t’lyl'll’ >Lr'l y i} Date 12/8/81 0-7639 This is to certify that the thesis entitled SPEECH FLUENCY AND LATERAL HAND ORGANIZATION IN STUTTERERS AND NONSTUTTERERS presented by Jay R. Greiner has been accepted towards fulfillment of the requirements for Masters 4233,33 in Deve] ogmenta] Psychology 91w 52% MSU LIBRARIES .g— RETURNING MATERIALS: Place in book drop to remove this checkout from your record. FINES will be charged if book is returned after the date stamped below. SPEECH FLUENCY AND LATERAL HAND ORGANIZATION IN STUTTERERS AND NONSTUTTERERS By Jay R. Greiner A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF PSYCHOLOGY Department of Psychology 1981 '- du mor COD SEQL and nOns; ABSTRACT SPEECH FLUENCY AND LATERAL HAND ORGANIZATION IN STUTTERERS AND NONSTUTTERERS By Jay R. Greiner Theoretical and empirical studies suggest mildly compromised left hemisphere functioning in stutterers during dysfluency, as well as general differences between stutterers and nonstutterers in cere- bral lateral organization. The present study compares lateralization ~of speech and nonspeech motor function in 40 adult males, 15 right- handed and £5 lefthanded stutterers and 15 righthanded and 5 left- handed nonstutterers. Measures included: (1) speech production dur- ing spontaneous speech, oral reading and singing; (2) bimanual handwriting of verbal and nonverbal engrams; and (3) concurrent speech (spontaneous, oral reading and singing) and unimanual sequential finger tapping. Results indicate: (l) greater dysfluency in stutters only during spontaneous speech; (2) stutterers' left hand (especially lefthanded stutterers) is significantly less organized and produces more mirror-image engrams than either hand of nonstutterers; (3) concurrent spontaneous speaking and unimanual finger sequencing pro- duced more stuttering and greater interference on correct finger sequencing in stutterers as compared to nonstutterers. Oral reading and singing produced significantly less interference on speech and nonspeech function in stutterers. Jay R. Greiner Consistent with Aldridge's (l981) hypothesis of central-level and peripheral-level processing in speech production, the present findings suggest differences in central-level attentional demands during spontaneous speaking in stutterers because of disrupted auto- maticity in peripheral-level processes. This work is dedicated to Marti, my friends, colleagues and family who have been understanding and supportive throughout this endeavor. ii ACKNOWLEDGMENTS This research was possible through the advice and shared knowledge of faculty and students and I am deeply grateful to every- one involved hithe completion of this thesis. I would especially like to thank each of the following individuals. Hiram E. Fitzgerald, chairperson of the Masters committee and major advisor throughout my graduate career at Michigan State Univer- sity. I am particularly grateful for his patient guidance through diverse areas of research and the interest he expressed in synthesis of medical science and psychology, culminating in this thesis on stuttering; Paul A. Cooke and Lauren J. Harris, my other committee members, for assistance in understanding the theory and therapy of language and speech disorders, particularly incorporating literature on stuttering into a broader neuropsychology base; Steven Gitterman and Roger Buldain for their computer pro- gramming skills and training sessions on the use of computerized methods of analysis; Karen Cornwell and Tom Stevenson for their concerned and intelligent input during collection and coding of the data, as well as the discussions we had relating this study to other research; Tom Johns, Terri Kummer, Jeff Bronstein, Erin Goldstein and Robert Tillotson for their assistance in collection of the data. iii The study was supported in part by an NIMH National Research Service Award 5T32 MH l4622-05(J.R.G.)andauiMSU Foundation Research Grant (HEF & PAC). iv N: k TABLE OF CONTENTS Page LIST OF TABLES ........................ vii LIST OF FIGURES ....................... viii INTRODUCTION ........................ l LITERATURE REVIEW ...................... 4 Dichotic listening differences between stutterers and nonstutterers . . ......... 4 Dichotic listening and reversed hemisphere functioning . ..................... 6 Bilateral tachistoscopic word perception ......... 7 Alpha asymmetry and hemisphere function in stutterers and nonstutterers .............. 8 Perceptual differences between stutterers and nonstutterers .................... 9 Speech production differences between stutterers and nonstutterers ................... 10 Measuring nonspeech manual lateralization ......... l3 Bimanual coordination in stutterers and nonstutterers ..................... l5 Concurrent speech and nonspeech unimanual motor performance ...................... l7 Motor sequencing in speech production .......... l8 Hemispheric representation and concurrent task interference ................... 20 Summary: General procedure and predictions ....... 22 METHOD ............................ 24 Subjects ......................... 24 Design .................. . ....... 24 Procedure ........................ 26 Data scoring ....................... 30 RESULTS ........................... 33 Pretest measures: Speech and bimanual coordination ...................... 33 Concurrent measures: Speech and unimanual sequential tapping ................... 39 V Page DISCUSSION ........ . ..... . ........... 59 APPENDICES ......... . ................ 67 A. Verbal and nonverbal stimuli for bimanual simul- taneous handwriting: numbers, letters and symbols . . 68 B. Project description letter to subjects, research informed consent form, individual information form, and sequential finger tapping complete instructions . . 73 REFERENCES .......................... 82 vi IO Table 10. ll. LIST OF TABLES Page Leuden square experimental design . . . . ........ 25 Speech fluency and speech rate in righthanded and lefthanded stutterers and nonstutterers during pretest spontaneous speech ...... . . . ...... 34 Speech fluency and speech rate in righthanded and lefthanded stutterers and nonstutterers during pretest oral reading ......... . ........ 35 Speech fluency and speech rate in righthanded and lefthanded stutterers and nonstutterers during pretest singing ..... . . . . . . . . . . . ..... 36 Pretest mean scores and ANOVA comparing stutterers and nonstutterers on bimanual simultaneous handwriting . 37 Pretest mean scores and ANOVA comparing righthanders and lefthanders on bimanual simultaneous handwriting . . 38 Means comparing righthanded and lefthanded stutterers and nonstutterers on mirror-image reversals during bimanual handwriting . . . . . . . . . . ........ 4O Multidimensional relationships and dimensional loading matrix between the dimensions of speech fluency and rate, correct and total sequential tapping, and number of finger omission errors while tapping . . ..... . . 42 Means and ANOVA comparing speech fluency in stutterers and nonstutterers during concurrent speech and bi- manual sequential tapping . . . ..... . . . . . . . . 43 Sheffe' post-hoc analysis of task means comparing speech fluency in stutterers and nonstutterers during concurrent speech and unimanual sequential tapping . . . 44 Means and ANOVA comparing correct and total unimanual sequential finger tapping and finger omission errors across four timeblocks of concurrent speech and sequen- tial tapping and across four tasks of silent nospeech, spontaneous speech, oral reading, and singing ...... 49 vii Figure 10. LIST OF FIGURES Sequential finger tapping apparatus used for concurrent unimanual sequential tapping and speech tasks . . . . . . . . . . . . . . . ....... Multidimensional relationships and factor corre- lations between speech and unimanual sequential finger tapping . . . . . . . . . . . . . . . . . . . . . Speech fluency during spontaneous speech, oral reading, and singing across four timeblocks of concurrent speech and unimanual sequential tapping ..... . . . Speech fluency in righthanders and lefthanders during concurrent speech and unimanual sequential finger tapping with the right and left hand . . . . . . . . . . Speech rate during spontaneous speech, oral reading, and singing across four timeblocks of concurrent speech and unimanual sequential tapping ........ Total unimanual sequential finger tapping in stutterers and nonstutterers during concurrent sequential tapping and spontaneous speech, oral reading, and singing . . . Correct unimanual sequential finger tapping in right- handers and lefthanders during concurrent speech and unimanual sequential tapping with the left hand . . . . Correct unimanual sequential finger tapping in right- handed stutterers and nonstutterers during concurrent speech and unimanual sequential tapping with the right and left hand . . . . . . . . . . . . . ..... . . . Correct unimanual sequential finger tapping in lefthanded stutterers and nonstutterers during concurrent speech and unimanual sequential tapping with the right and left hand . . . . . . . . . . . . . . . . . . . . . . . Total number of finger omission errors during concur- rent speech and unimanual sequential tapping with the right and left hand across all subjects . ....... viii Page 28 41 45 47 48 50 51 53 54 55 Figure Page ll. Total number of finger omission errors in right- handers and lefthanders during concurrent speech and unimanual sequential tapping with the right and left hand . . . . . . . . . . . . . . . . . . ..... 56 l2. Total number of finger addition errors in righthanders and lefthanders during concurrent speech and unimanual sequential tapping with the right and left hand . . . . 58 ix INTRODUCTION The assertion that cerebral lateral organization is related to stuttering originated from theories emphasizing incomplete lateral- ization or lack of cerebral dominance (Orton, 1927; Travis, l93l), and from clinical reports linking stuttering to forced changes in children's handedness (Ballard, l9ll; Claiborne, l9l7; Bryngelson, l935; Bloodstein, l975). According to the Orton-Travis hypothesis, dominance of one hemisphere over the other is necessary for estab- lishment of the temporal rhythm of speech. Stutterers were thought to lack dominance and, therefore, their speech musculature was in- fluenced by independent functioning of the left and right cerebral hemispheres. Early theories relating lateral organization to stuttering assumed handedness or hand preference to be a reliable index of the degree and direction of the lateralization of speech function (Bloodstein, 1975). Many aspects of the Orton-Travis theory were discarded during the l930's and l940's because investigators failed in their attempts to distinguish stutterers from nonstutterers on the basis of later- ality or handedness (Bloodstein, l975; Danield, l940). Recent research, however, has stimulated fresh interest in lateralization theories of stuttering (Jones, 1966; Curry & Gregory, 1969; Brady & Berson, l975; Sussman & MacNeilage, l975; Moore, 1976; Moore & Lang, l l977; Moore & Haynes, 1980; Zimmermann & Knott, l974). Much of con- temporary research uses the dichotic listening task or the tachis- toscopic word perception task. Hemispheric involvement is inferred from measures of speech perception, electroencephalographic recording of brain wave activity, or motor performance. Relatively little attention is given to handedness as an etiological factor in stuttering or, more specifically, to hand skill use as an indicator of cerebral organization or disorganization in stuttering. Because some stutterers differ from nonstutterers during assessment of lateralization of perceptual functions, researchers became interested in whether or not similar differences exist in hemisphere control of independently and simultaneously occurring speech and nonspeech manual motor tasks. Sussman & MacNeilage (l975) found that among stutterers and nonstutterers in whom no differences were found in speech perception, the stutterer's hemispheric dominance for speech production was the reverse of the nonstutterers, i.e., stutterers were more likely to show a left ear (right hemisphere) advantage. In the same study, the stutterers demonstrated a left ear (right hemisphere) advantage in a manual tracking task with the right hand. This greater right hemisphere involvement in manual pursuit auditory tracking might be consistent with the Orton-Travis theory which identifies the stutterer's main failing as a lack of motor lead control. The greater right hemisphere involvement is further related to reports of mirror-writing in stutterers (Bryngelson, l935; Bryngelson & Rutherford, l937; Greiner et al., 1981). Mirror-writing during simul- taneous hemisphere activation is reported to be a frequent occurrence after left hemisphere injury that results in transfer of language function to the right hemisphere, resulting in right hemisphere con- trol of left hand performance (Corbalis & Beale, 1976). Evidence exists for left hemisphere impairment in stutterers (Rosenbeck et al., 1978; Luchsinger & Arnold, 1965, Schiller, 1947; Rosenfield, 1972; Shtremel, 1963, Daly & Smith, 1979), and more specifically Wood et al., (1980) indicate the impairment to be transient as indicated by cerebral blood flow measurements. Transient left hemisphere dysfunction would explain the lack of right ear advantage in some stutterers as well as the on-off nature of the stuttering moment. Studies of concurrent speech and unimanual finger sequencing have accumulated demonstrating generalized and lateralized depression in finger sequencing during speech, especially in righthanders (McGlone, 1972; Lomas & Kimura, 1976; Hicks et al., 1975; Hicks, 1976; Hicks et al., 1978; Summers & Sharp, 1979). In addition, research has addressed the issue of limited cerebral space during speech and non- sequential manual motor tasks, with the conclusion that effortful motor tasks compromise manual motor performance (Kinsbourne & Cooke, 1971; Kinsbourne & MacMurray, 1978; Kinsbourne & Hiscock, 1977; Hiscock & Kinsbourne, 1978; Ramsay, 1979). The remaining literature review will cover in detail the re- search that differentiates stutterers from nonstutterers during per- ceptual and production tasks involving language. LITERATURE REVIEW Dichotic listening differences between stutterers and nonstutterers In 1966, the Orton and Travis explanation was reactivated in part by Jones' study of four stutterers who appeared to have repre- sentation of speech bilaterally. Using the Nada technique (Nada & Rasmussen, 1960), Jones injected sodium amytal into the left and right carotid arteries, in all cases producing loss of speech irre- spective of the side of injection. The results of Jones' study may have been affected by the fact that all four subjects had unilateral cerebral pathology and three of the four were lefthanded (Moore, 1976). Although stuttering may have existed as a consequence of injury or as a consequence of handedness (lefthanders show more bilateral representation of speech), Jones' results did lead to renewed interest in cerebral dominance theories of stuttering. Widespread use of Nada technique to examine the relationship of cerebral lateralization and speech did not occur because of the invasive nature of the procedure. Furthermore, at about the same time, Doreen Kimura (1961, 1967) adapted Broadbent's (1954) dichotic listening method for use as a means of assessing lateralization of perceptual functions. The technique requires simultaneous activation of the hemispheres or a condition of perceptual rivalry during which crossed auditory pathways are seen as more effective than uncrossed. This is manifest in a right ear advantage (REA) for linguistic stimuli processed in the left hemisphere and a left ear advantage (LEA) for nonlinguistic or nonverbal stimuli processed in the right hemisphere. Using the dichotic and monotic listening technique, Curry and Gregory (1969) administered four different tasks to 20 stutterers and 20 nonstutterers all of whom were righthanded and nonbraindamaged. The four listening tasks were: 1) Dichotic Nord Test, 2) Monotic Nord Test, 3) Dichotic Environmental Sounds Test, 4) Dichotic Pitch Test. The Curry and Gregory results indicate the expected cerebral dominance for nonstutterers in that 75% showed a REA on the Dichotic Nord Test. However, only 45% of the stutterers received higher right ear scores, which the authors interpreted as lending support for the theory that stutterers lack cerebral dominance. The right ear superiority for nonstutterers was found only on the Dichotic Nord Test. Moreover, the mean between-ears difference scores on the Dichotic Nord Test for nonstutterers were more than double the scores for stutterers, lending support to the view that stutterers have incomplete lateralization. In addition to the possible incomplete lateralization of hemisphere function, a reversal of ear advantage occurs in some stutterers. As part of their 1969 study, Curry and Gregory found that 55% of the stutterers had reversed ear advantage in the Dichotic Nord Test (i.e., these stutterers performed consistent with predictions for a LEA). Brady and Berson (1975) demonstrated findings similar to Curry and Gregory (1969) in which a REA for verbal stimuli was not found in stutterers. However, Brady and Berson also found subgroup of LEA stutterers and when this LEA subgroup was removed, the remain- ing stutterers had nearly identical right ear scores with the non- stutterers, i.e., a right ear advantage. This subgroup of stutterers with reversal of ear advantage in dichotic listening also was found by Quinn (1972) in an attempt to replicate Curry and Gregory (1969). Quinn found that 20% of the stutterers had reversed ear advantage (LEA); however, the other aspect of the Curry and Gregory results relating to incomplete lateralization was not replicated by Quinn in that the interaural difference scores did not differentiate stutterers from nonstutterers. 0n the basis of the Quinn study as well as Slorach and Noehr (1973), it appears that stutterers and nonstutterers cannot be differentiated on the basis of the extent of cerebral lateraliza- tion for speech. It does seem, however, that a subgroup of stutterers can be differentiated from nonstutterers on the basis of reversal of ear advantage for linguistic processing. Dichotic listening and reversed hemisphere‘TUnctioning Curry and Gregory (1969) cite evidence (Kimura, 1961) that reversals in ear superiority on a dichotic task, as occurred in the LEA subgroup of stutterers, can occur in known cases of reversals in hemispheric functioning as determined by sodium amytal tests. Curry and Gregory (1969) also cite evidence (Goodglass, 1967) that 62% of cases of known left hemisphere damaged persons (13 out of 21), ob- tained higher left ear scores on a dichotic digit test. Whether the reversal in hemispheric functioning found in these cases and in the stutterers is due to left hemisphere cortical dysfunction, develop- mental variation, or genetic transmission is an empirical question, yet unanswered. Bilateral tachistoscopic wordgperception Sussman & MacNeilage (1975) attempted and failed to confirm previous findings of the lack of a REA for stutterers on a verbal dichotic task; however, they did demonstrate a lack of REA on a measure of speech production. 0n the basis of these results they conclude that stutterers and nonstutterers differ in speech pro- duction but not in speech perception. The variability in findings on the dichotic tasks with stutterers was addressed by Moore (1976), who argued that the difference might be related to the nature of the linguistic stimuli used. All studies that failed to find a REA in stutterers employed meaningful linguistic stimuli, and studies (Sussman & MacNeilage, l975; Cerf & Prins, 1974) that found similar performance on dichotic verbal tasks used less meaningful nonsense syllables as stimuli. Using meaningful linguistic stimuli, Moore (1976) investi- gated differences between stutterers and nonstutterers in hemis- pheric processing by using bilateral tachistiscopic procedures and comparing visual half-field preferences. Moore found a right half- field preference/left hemisphere processing of linguistic stimuli in normal subjects; however, stutterers did not demonstrate a difference between their mean right half-field scores and their mean left half- field scores. Furthermore, significantly more stutterers than non- stutterers obtained a left half-field percentage score greater than 50%. Moore also found a clear reversal of visual half-field in that 53% of the stutterers had higher left half-field scores. Alpha asymmetry and hemisphere function in stutterers and nonstutterers Nhen righthanded nonstutterers process meaningful linguistic information, they tend to show: 1) a right ear superiority for ver- bal dichotic stimuli; 2) a right visual half-field preference in tachistoscopic tests; and 3) suppression of alpha activity of the left hemisphere indicative of left hemisphere processing of the linguistic stimuli (Moore & Lang, 1977). In attempting to further differentiate suttterers and non- stutterers, Moore & Lang (1977) examined alpha activity over the left and right hemisphere when processing meaningful linguistic information. Specifically, they compared the performance of right- handed stutterers and nonstutterers on the third area of suppression of alpha activity over the left hemisphere, indicative of left hemisphere processing. Percent alpha time over each hemisphere during five oral readings of two different passages was examined. The Moore and Lang results indicate that a significantly larger proportion of nonstutterers had greater percent alpha time over the right hemisphere as compared to stutterers. Conversely, a significantly larger proportion of stutterers had greater percent alpha time over the left hemisphere. Decreased alpha time over the right hemisphere in stutterers was interpreted as indicating dependence on visual-spatial components during linguistic processing, in contrast to dependence on verbal components processed by the nonstutterers. It is important to note that Moore and Lang measured hemi- sphere activity preceding a speech production task and interpreted the differences as differences in processing. In contrast, another electroencephalographic study employing the contingent negative variation (CNV) procedure (Zimmermann & Knott, 1974), demonstrated differences between stutterers and nonstutterers only at the lateral electrode site. Compared to stutterers, nonstutterers showed a larger shift in the left hemisphere during speech and nonspeech (expectancy), suggesting that the differences in left hemisphere activity are occurring preceding speech as well as during speech production. Perceptual differences between stutterers and nonstutterers Summary: The following conclusions are suggested from this review of research studies in dichotic listening, tachistoscopic perception, and electroencephalographic activity preceding and during speech: First, the Orton-Travis model of lack of cerebral dominance or of incomplete lateralization of hemisphere functioning in stutterers is not supported; 10 Second, the important difference between stutterers and non- stutterers exists in a subgroup of stutterers demonstrating a reversal of hemispheric processing of meaningful linguistic information as well as a reversal of hemispheric functioning preceding and during speech production. During hemispheric rivalry in processing language, some stutterers demonstrate typical left and some right activation. Speech production and hemispheric control and activation in stutterers and nonstutterers also has been explored recently and indicates further differences between stutterers and nonstutterers in mechanisms of speech production and lateralization of motor skills. Speech production differences between stutterers and nonstutterers Based on a review of research on speech perception in stutterers, it appears that a certain percentage of stutterers process meaningful linguistic information in the right hemisphere to a greater degree than is typical in righthanded nonstutterers. Based largely on observation of the language of aphasic patients, Benton (1972) describes these patients as incapable of left hemisphere, proposi- tion speech. However, they are capable of speech production that can be described as emotional, interjectional and automatic. In relation to right hemisphere function in speech, Harris (1973) cites evidence that patients with lesions of the left hemisphere or with total hemispherectomy still are capable of speech production (although some are impaired), with the inference that the production involved is mediated by the right hemisphere. Such patients can sing, swear, 11 and utter simple, familiar words and phrases. These studies of clinical populations led researchers to conclude that the left hemi- sphere was the major or lead hemisphere for speech; however, if the left hemisphere was compromised, the right hemisphere could be in- volved in speech production because of verbal engram bilateral place- ment during language development (Harris, 1973). Examination of the fluent speech of stutterers reveals simi- larities with right hemisphere speech production. Research of the speech production of stutterers indicates that therapeutic reduction of stuttering may be associated with certain modification of vocaliza- tion (Ningate, 1969). Important consideration should be given to similarities in right hemisphere speech to modified vocalizing which decreases stuttering. Examples of this modified vocalizing include prolongation of syllables, rhythmic or metronomic speech, monotonic speech, whispering, and continuous phonation. The reduction of stut- tering during singing has been discussed as "one of the universal facts about stuttering" (Ningate, 1979). In 1976, Healey, Mallard and Adams attempted to determine whether the reduction of stuttering during singing was a result of modification of vocalization factors or was a result of the familiar- ity of the melodies being sung. In condition one, the subject read conventional lyrics ("Home on the Range," "God Bless America," and "Silent Night"). In condition two, the subject sang these conven- tional lyrics; in condition three, the subject read aloud with new, unfamiliar lyrics; and in condition four, the subject sang new lyrics to conventional melodies. 12 The results indicated that the greatest reduction in stutter- ing occurred when the stutterers were singing familiar lyrics with familiar melodies. Healey et al., concluded that fluent vocalizing during singing in stutterers is related to familiarity of the melody and lyrics in addition to modification of the vocal apparatus. Other authors (Brayton & Conture, 1978) suggest further study of temporal changes in stutterers' speech during fluency-inducing speech such as singing. Measuring speech lateralization during singing may be one way to account for hemispheric processing during types of vocalizing with inherent rhythm, and with variable neuromotor demands (Zimmer- man, 1980). Measuring speech lateralization In an effort to provide additional evidence of differences between stutterers and nonstutterers in speech production, Sussman & MacNeilage (1975) experimented with the same group of subjects reported in the earlier study of dichotic listening, in which no differences were found between stutterers and nonstutterers on dicho- tic speech perception. They were interested in comparing stutterers and nonstutterers on a measure of speech production known as pursuit auditory tracking. The task of the subject in the pursuit auditory tracking task is to control the motor system regulating articulation (jaw tracking) and that regulating nonspeech motor activity (right hand tracking). The task involves moving the jaw or right hand in described directions so as to match a tone being controlled with the frequency fluctuations 13 of a target tone; the tones being dichotically presented. For exam- ple, jaw depression decreased the frequency of the to-be-controlled tone and jaw elevation increased the frequency. Nonstutterers showed a clear REA on the jaw tracking task, which Sussman and MacNeilage interpreted as left hemisphere control of the articulatory motor system. However, the stutterers did not demonstrate a REA, interpreted as the lack of clear left hemisphere control of the speech production mechanisms. The proportional differ- ences from this study indicate left processing in nonstutterers and bilateral processing stutterers. Measuring nonspeech manual lateralization From the Sussman & MacNeilage (1975) study, a higher percen- tage of stutterers have right hemisphere advantage for speech- related tasks, and in addition, stutterers demonstrated a left ear, or right hemisphere advantage for the nonspeech motor task of manual pursuit auditory tracking. Based on this finding of right hemisphere involvement, in some stutterers, for processing stimuli in manual pursuit auditory tracking, stutterers and nonstutterers can be differentiated on the basis of lateralization of manual motor skills. The importance of manual activity was noted as early as 1927 by Samuel Orton. In reporting studies in stuttering, Orton 14 described a severe stutterer who spoke fluently when writing with his left hand. I have tried the experiment of making him write with the left hand while he is attempting to speak, with the aim of thus determining a consistent right cerebral lead. During this action he can talk with comparative freedom, though slowly, of course, in order not to get ahead of his pencil. Nithout this guide, he has the greatest difficulty. (p. 672) Orton indicates that this supports the theory that stuttering is an expression of confusion in cerebral dominance. However, handedness or hand preference has not proven to be a reliable index of lateralization of speech function. Recently, researchers interested in a possible genetic etio- logy for stuttering administered a handedness questionnaire to stutterers and nonstutterers (Records, Heimbuch & Kidd, 1977). There was no indication of greater lefthandedness among stutterers than nonstutterers using univariate analysis. However, a MANOVA analysis of these same data, demonstrated a slight, although statistically insignificant, increase in the proportion of lefthandedness in stutterers. Records et a1. (1977) suggest that previously reported differences between stutterers and nonstutterers might have been due to additive effects of the slight increase in lefthandedness found in both stutterers and males. The male to female ratio of stutterers is approximately 4:1 and therefore the reported increase in lefthanded- ness in stutterers may be related to sex differences in handedness with a higher incidence of lefthandedness in males. If stutterers and nonstutterers cannot be differentiated on the basis of lefthandedness per se, then other possibilities need to 15 be examined. For example, it may be possible to differentiate stutterers from nonstutterers on the basis of differences in lateralization of manual motor skills. Bimanual motor coordination in stutterers and nonstutterers Bimanual motor coordination as required in simultaneous handwriting tasks has produced mirror writing in stutterers to a greater extent than in nonstutterers (Bryngelson, 1935; Greiner et al., 1981). Greiner et al. (1981) report that during simultaneous handwriting, 64% of adult stutterers (n=11) and none of the non- stutterers (n=ll) demonstrated reversal of numbers with their non- dominant or nonpreferred hand. In addition, stutterers had poorer organization of the numbers written with their nonpreferred hand. The occurrence of mirror writing in stutterers has been interpreted as indicating dominant hemisphere impairment, resulting in the necessity for transfer of language function to the right hemisphere (Corballis & Beale, l976). Rasmussen & Milner (1977) suggest limita- tions on conditions during which this transfer will actually occur. From a series of studies, these authors conclude that childhood injuries to the left hemisphere incurred after age five did not result in transfer of speech representation to the right hemisphere, but prior to age five transfer was possible. Recovery of speech function in children age six and older is achieved by an intrahemi- spheric reorganization following the left hemisphere injury (Rasmussen & Milner, 1977). l6 Impaired left hemisphere function compromises motor lead control or cerebral dominance needed for bimanual coordination. Evidence for left hemisphere impairment in stutterers has mounted (Rosenbeck et al., 1978; Luchsinger & Arnold, 1965; Schiller, 1947; Rosenfield, 1972; Shtremel, 1963). Recently, Wood et a1. (1980) reported a decrease in cerebral blood flow in Broca's area of the left hemisphere during stuttering. However, when stutterers' speech was fluent, no decrease in cerebral blood flow was found. This transient hemisphere activity might explain the on-off nature of the stuttering moment and the direct association of stuttering blocks with increased effort and motor tension through the mechanism of diminished cerebral blood flow. In relation to this view of stuttering as transient impairment, Greiner et a1. (1981) report the occurrence of mirror writing to be sporadic and transient, i.e., not all "potentially reversible" numbers were actually reversed by stutterers. Such transient mirror writing suggests a shift in motor lead control, a transient loss of cerebral dominance, or a relation- ship to mechanisms of hemispheric control of the lateral gradient of attention (Kinsbourne, 1970). Further exploration of the components of attention and effort during hemispheric activation has been accomplished by a series of time-sharing speech and nonspeech motor task studies. These dual-task studies address the issue of accessible cerebral space in pertinent motor areas, during effortful motor tasks (Kinsbourne & Cooke, 1971; McGlone, 1972; Lomas & Kimura, 1976; Kinsbourne & MacMurray, 1978; Kinsbourne & Hiscock, l977; Hiscock & l7 Kinsbourne, 1978; Ramsay, 1979; Hicks et al., 1975; Hicks, 1975; Hicks et al., 1978; Summers & Sharp, 1979). Concurrent speech and nonspeech, unimanualgperformance The evidence for interference of nonspeech manual activity during speaking may be summarized as follows: 1) Spontaneous move- ments of the right hand in particular are facilitated during speaking but not during an equivalent nonspeech vocalization such as humming (Kimura, 1973; Lomas & Kimura, 1976); 2) Nhen the manual task is more specific rather than spontaneous as in dowel balancing or sequen- tial typing tasks, the effect is depressed manual performance of the right hand (Kinsbourne & Cooke, 1971; Hicks, 1975; McGlone, 1972; Lomas & Kimura, 1976). As a result of these experiments on time-sharing between speaking and unimanual tapping, the lowered tapping rate by the right hand has been interpreted as indicating left hemisphere special- ization for speech with the assumption that there is interference between concurrent activities controlled by the same hemisphere (Kinsbourne & Hiscock, l977; Ramsay, 1979). Hicks et a1. (1975) discuss the mechanism of lateralized effects in the following way. Nhen two cerebral control centers are concurrently active, as in sequential tapping and unsequenced, spontaneous speech, they interfere with each other inversely with their anatomical distance from each other, and directly with the amount of activity required of each center for the particular motor task. 18 In addition, Lomas & Kimura (1976) suggest that the inter- action between speaking and manual activity is related to the "limited cerebral space" concept in that both speech and right hand movement are controlled by the same hemisphere. More specifically, these authors conclude that the overlap in the left hemisphere is for speech and rapid movement sequences of the contralateral hand. They raise the further possibility that rapid positioning of a limb or parts of a limb, with minimal visual guidance, is the factor related to lateralized decrement in concurrent speaking tasks. If this is true, the contribution of the left hemisphere to speaking may also be in the control of rapid placement of the articulatory musculature. Motor sequencing in speech production Dysfluent speech has been described as "temporal disruption in the unity of motor patterning" (Van Riper, 1971), and supraglottal articulatory activity has been implicated as a major factor in dis- coordination and disruption of motor sequencing. Phonation is the central factor in speech and is a function of integration and coordi- nation of the complexity of glottal laryngeal factors, subglottal respiratory processes, and supraglottal articulation. The specific phonetic and linguistic aspects of a particular language are especially important because phonetic segment duration is determined physiologically by the rates of movement of the supraglottal arti- culators. Furthermore, Ningate (1977) has described stuttering as a defect in transition from one phoneme to another. The consonant- vowel-consonant combinations most often are the source of the l9 stuttering blocks, and it is these C-V-C combinations that require rapid sequencing and differentiation phonetically. Hypothetically, the phonetic transition defect is most pronounced during speech pressure and communicative stress which are typically associated with increased neuromotor Speech movement (Zimmerman, 1980). Speech production is a variable dimension described by rate, rhythm, and intonation of speech as well as vocal intensity. Thus, slowing the rate of speech, regularizing the rhythm of speech, speaking in a monotonic voice, whispering, or speaking with much increased vocal intensity all have been shown to reduce stuttering. The vocalization modification hypothesis suggests that modified vocalizing induces fluency. Zimmerman (1980) suggests that the overriding change is in reduction of movement variability as it occurs in the simplified neuromotor demands of whispering or in the imposed rhythm of singing. The three vocalization tasks used in the present study vary on this speech production dimension of modified vocalizing and on temporal sequencing requirements. These tasks are spontaneous speech, reading aloud, and singing a familiar melody. The vocalization tasks vary in the degree to which they challenge the motor organization and sequencing ability of the speech apparatus. Biological hemispheric representation of speech is another factor to be considered in predicting dysfluency in the concurrent speech and unimanual sequencing task. Lomas & Kimura (1976) report that speech associated with the decreased right hand tapping con- tained too few errors for any meaningful analysis. However, Sherrard 20 (1975) reports dysfluent speech in nonstutterers during a concurrent speech and nonspeech task. Employing the signal detection procedure, Sherrard has described stuttering as "false alarm" responding and has demonstrated that during performance of two tasks simultaneously (reading a text aloud and following a stylus maze with the right hand), normal nonstutterers had dysfluent speech. All subjects in Sherrard's study were righthanded as were those in Lomas & Kimura's (1976) study. Sherrard (1975) likened the simultaneous performance of two tasks to a divided attention condition, which previously had been shown to increase the probability of false alarm responding in a signal detection task. Therefore, stuttered speech produced by nonstutterers, and by implication, stuttering in stutterers, may be associated with false alarm responding. Hemispheric representation and concurrent task interference Oldfield (1969) hypothesized that the hands are each specialized for specific functions which are especially important during bimanual performance: the preferred hand is superior at leading or initiating a sequence, while the nonpreferred hand is better at following or supporting the movements of the preferred hand (Hicks et al., 1975). Although McGlone (1972) confirmed the Oldfield hypothesis on bilaterally synchronized sequential tasks, less consistent preferred hand superiority occurred during a uni- manual sequencing task. 21 Hicks et a1. (1975) report that vocal rehearsal of verbal lists concurrent with unimanual sequential tapping interfered more with the right than the left hand in normal speakers. The import- ance of this finding as well as work of other researchers who report lateralized effects of unimanual sequential tapping and speech (Lomas & Kimura, 1976; Summers & Sharp, 1979; Hicks et al., 1978) is that the effects of dual-task or concurrent speech and nonspeech unimanual sequencing tasks may be lateralized, but may also be generalized; that is, general interference of speech or tapping may occur. For example, Hicks et a1. (1975) report that silent rehearsal did not produce the lateralized hand effect like vocal rehearsal but did produce generalized interference of manual sequencing. To examine possible generalized effects on speech and non- speech, all aspects of sequencing errors were analyzed in the present study including errors in speech and unimanual sequencing. Dys- fluent speech consists of deviation in motoric sequencing, speci- fically defined as either repetitions of a word or partword or silent or audible prolongation of words. In general, researchers report whether or not subjects make errors on sequential finger tapping tasks but do not report what such errors were. The present study examined all finger tapping errors for either omissions or additions in any one particular sequence. 22 Summary: General procedure andgpredictions The present study was designed to use the unimanual sequen- tial tapping task within a time-sharing tapping and speech task, with the speech tasks designed to vary in the degree to which they en- gage lateralized speech-control mechanisms. The spontaneous speech task is most dependent on left hemisphere speech representation and temporal programming. Singing is assumed to be represented mainly in the right hemisphere and therefore is differentially lateralized to the right (Gordon & Bogen, 1974). Oral reading is lateralized to the left hemisphere, but not to the degree of spontaneous formulation of speech because of visual-spatial aspects of reading and fewer temporal ordering requirements. This hierarchical structuring of speech tasks is based on consistent interindividual hemispheric representation of types of speech and speech performance. Nithin the stuttering and non- stuttering population, homogeneity of neuropsychological functioning is unlikely because handedness confounds cerebral organization in lefthanders and righthanders (Daly & Smith, 1979; Sussman & MacNeilage, 1975; Kimura, 1973; Branch et al., 1964; Goodglass et al., 1954). In addition to the speech tasks, a silent, nospeech condi- tion was tested in the present study in order to examine effects of unimanual sequencing outside the dual-task paradigm. Based on the preceding literature review, the following predictions were made: 23 Simultaneous Handwriting; l. Stutterers will have significantly poorer structural organiza- tion in their bimanual handwriting than will nonstutterers, Pretest Speech Tasks; 2. During pretest speech tasks, stutterers will be more dysfluent and speak slower than nonstutterers during spontaneous speech, but will not differ from nonstutterers during oral reading and singing. Concurrent Tasks; 3. During concurrent tasks, stutterers and nonstutterers will differ in speech fluency and rate, with the most dysfluency occurring during spontaneous speech, followed by oral reading, then singing. The slowest speech rate will occur during spontaneOus speech, followed by singing, then oral reading. 4. During concurrent tasks, stutterers and nonstutterers, right- handers and lefthanders will differ in the amount of speech inter- ference on unimanual sequential finger tapping. Spontaneous speech will produce the most interference, followed by oral reading, then singing. METHOD Subjects The subjects were 40 males, including 15 righthanded stutterers (mean age 25.9 years; range 16-54), 5 lefthanded stutterers (mean age ' 22.0 years; range 16-36), 15 righthanded nonstutterers (mean age = 27.2 years; range = 16-34) and 5 left- handed nonstutterers (mean age = 26.2 years; range = 20-42). The stutterers were recruited from the Michigan State University Audiology and Speech Sciences Clinic. The nonstutterers were recruited from undergraduate psychology courses at Michigan State University. Informed consent was obtained prior to partici- pation of subjects in the study (see Appendix 8). Design The sequence of events involved assessment of pretest speech and bimanual coordination followed by concurrent speech and unimanual sequential finger tapping. For the concurrent tasks, a Leuden Square Experimental Design was used which involved 2 condi- tions and 4 tasks. The sequences are shown in Table l. The experimental design randomly distributed the order of concurrent speech task presentation (1 = silent tapping, 2 = tapping while spontaneously speaking, 3 = tapping while reading aloud, 4 = tapping while singing) over four (4) blocks of eight trials per block. The first 2 time blocks of 16 trials for subjects assigned 24 25 Table l Leuden Square Experimental Design Subject Subject Condition A (l) (2) (3) (4) Condition 8 (5) (6) (7) (8) n=4O Left, Right 1 2 3 4 Right, Left 1 2 3 4 2 4 l 3 2 4 l 3 3 l 4 2 3 l 4 2 4 3 2 1 4 3 2 1 Left, Right 2 l 4 3 Right, Left 2 1 4 3 4 2 3 1 4 2 3 1 l 3 2 4 l 3 2 4 3 4 l 2 3 4 l 2 Right, Left 4 3 2 1 Left, Right 4 3 2 l 3 1 4 2 3 l 4 2 2 4 1 3 2 4 1 3 l 2 3 4 l 2 3 4 Right, Left 3 4 1 2 Left, Right 3 4 1 2 1 3 2 4 l 3 2 4 4 2 3 1 4 2 3 l 2 l 4 3 2 1 4 3 26 to Condition A involved tapping sequences with the left, then right hand. The 3rd and 4th time blocks involved right, then left hand tapping for 16 trials. Condition 8 was exactly the opposite of Condition A with respect to which hand would lead during the time- block, but used the same randomization of order of concurrent speech tasks. Procedure Pretest speech fluency and rate. Pretest speech fluency and rate were assessed with the Stuttering Severity Instrument (Riley, 1972). The subject was asked to speak spontaneously for 3 minutes, sing two rounds of the song "Row, row, Row your boat," and read aloud the following passage: If you throw a stone into a quiet pond, you see small waves start out from the place where the stone fell into the water. These waves spread steadily outward in circles. A chip of wood floating on the water will bob up and down as the waves pass. This happens because motion is handed on from the stone to the chip by means of the waves. After the set of waves has gone by, the surface of the water is again quiet and the chip is still. The waves on the pond give you a picture in slow motion of what happens when you hear a sudden noise. An exploding firecracker disturbs the air around it, just as the stone disturbed the water. Naves move out through the air in all directions. Nhen these waves hit your ear, they pass some of the motion on to your eardrum, and you hear the sudden noise. During pretest speech, all vocalizations were recorded on a Panasonic taperecorder for later analysis of fluency and rate. Determination of handjpreference and bimanual coordination. Nonspeech manual performance was assessed using the Harris Tests of Lateral Dominance (1957) to determine placement of subjects in hand 27 preference categories. Bimanual performance was assessed using a simultaneous handwriting task, modified from Harris (1957) and requiring bimanual coordination. The stimuli for this task were the numbers one to twelve and a set of 50% single and 50% double digit numbers, letters, and symbols chosen as language engrams represent- ing left (numbers and letters) and right (symbols) hemisphere func- tion. (See Appendix A.) Nonspeech bimanual performance involved the subject sitting at a table with a pencil in each hand. Subjects were told that they would not be able to see their hands while they were writing the numbers one to twelve with both hands simultaneously. Subjects then were instructed to write the numbers from one to twelve as quickly as possible without going off the sides or bottom of the page. An identical procedure was used for the additional 36 stimuli which were randomly ordered and presented to the subject one at a time. Subjects were required to copy the individually presented number(s), letter(s) or symbol(s) with both hands simultaneously as quickly as possible without going off the sides or bottom of the page. Concurrent speech and unimanual sequential finger tapping. The unimanual sequential finger tapping task was modified from pre- vious research (Lomas & Kimura, 1976). A screen was used to occlude subject's view of the sequential tapping apparatus (see Figure 1) during the study. Each of the 8 finger keys was digitally programmed by a DEC LSI 11/03 general purpose minicomputer located in an adjacent 28 .mxmmp commam use mcwaqwg meucmacmm szcmswca pcmggzocoo com tom: mzumgmaam mcwnamp cmmcwm pawucmsamm ._ mesmwu .0 mo\: .3 41/: _ 29 room. The computer recorded finger taps and latency (milliseconds) between taps. These data were stored on a floppy disk system and printed for later scoring and analysis. Each of the right and left thumb keys also was programmed to light up and then switch off as an indicator of the beginning of a trial as well as to indicate whether the right or left hand would be tapping during that trial. The procedure for the concurrent speech and unimanual sequen- tial tapping was as follows. Each subject wasseated facing the sequential tapping apparatus and was given one 30—second trial with each hand separately. At this time, the subject was permitted to see the finger keys. This initial practice trial was followed by one additional 30-second practice trial with each hand separately, with the subject now prevented from seeing the finger keys, as he would be throughout the study. Instructions were varied according to whether subjects were assigned to Condition A (start unimanual task with right hand) or Condition 8 (start with left hand). (See Appendix B for complete instructions.) Subjects were instructed to rest the palm of each hand on the tapping apparatus while tapping so as to lessen any effects due to typing or piano playing experience. The subjects then were instructed to tap sequentially as fast as they could beginning with their index finger and tapping outward to the small finger, and then to return to the index finger for a new sequence. The subjects also were urged to avoid errors in sequencing. 30 Data scoring Pretest speech fluency and rate were assessed with the Stuttering Severity Instrument (Riley, 1972) on three tasks: spon- taneous speech, reading aloud, and singing. Speech fluency was scored by skipping the first 25 words and then counting the number of dys- fluent words in the next 100 words. An utterance was judged to be dysfluent if a whole word or part of a word was repeated, or silently or audibly prolonged. The percentageof dysfluent words was then calculated. The speech rate was defined as the number of words spoken per minute. Nonspeech motor performance during simultaneous handwriting was scored based on the following criterion. Subjects were given 10 points initially for each number, and points were deducted on the following bases: 1) one point for lack of general alignment of numbers or scattered numbers; 2) one point for overlap from one number to the next; 3) one to three points depending on degree of incompleteness of the number; 4) one to two points depending on the lack of appropriate and necessary structure; 5) one to two points depending on lack of general symmetry of the number; and 6) one point for lack of general legibility of the number. These same criteria were applied to letters and symbols. Reversed or mirror-written numbers, letters, or symbols were rated on organization aside from the reversal, and the number of reversals was calculated separately. For the purpose of rating, the data was randomized by hand and subject so that the rater would not know whether the numbers, 31 letters, or symbols were written by a right or left hand or by a stutterer or nonstutterer. Two independent raters received one practice rating session with the experimenter before the actual rating task. Pearson correlations were used to calculate the interrater reliability across the two raters for each number, letter and symbol. The reliability across both raters and all stimuli was .95. The range of correlations was .85 to 1.00, with poorer relia- bility for numbers with poorer organization and perfect correlation with engrams that were written close to the standard set of numbers, letters, and symbols used for rating (see Appendix A). The mean score across the two raters for each number, letter, and symbol was then used in the final analysis of handwriting organization. This simultaneous handwriting rating criterion has been used previously in a study of simultaneous handwriting (Greiner et al., 1981) with mean interrater reliability across three raters of .96. The concurrent unimanual sequential tapping data was stored on L51 11/03 floppy disks, and printed copy was scored with atten- tion given to the following variables: (See Appendix D for example.) 1. number of keys tapped per trial, 2. number of keys tapped in correct sequence per trial, 3. number of keys omitted in any particular sequence for fingers 1, 2, 3, and 4 per trial, 4. number of keys added in any particular sequence for fingers 1, 2, 3, and 4 per trial, 5. number of keys omitted across all fingers per trial, 6. number of keys added across all fingers per trial, 32 7. number of errors across all fingers (omissions or addi- tions per trial. RESULTS Pretest Measures: Speech and Bimanual Coordination No significant differences were found between stutterers and nonstutterers or between righthanded or lefthanded subjects for speech fluency or speech rate during oral reading or singing; however, nonstutterers were significantly more fluent than stutterers during spontaneous speech. Initial analysis of spontaneous speech indicated no differences between stutterers and nonstutterers but when dysfluency contributed by 'starters' (e.g., "uh...") was not included in the analysis, nonstutterers were significantly more fluent. (See Table 2, 3 & 4.) Bimanual handwriting produced significant differences between stutterers and nonstutterers (see Table 5). Stutterers performed significantly better than nonstutterers during simultaneous hand- writing of numbers and letters when using their right hand, but the two groups did not differ when writing symbols with the right hand. Conversely, stutterers performed significantly worse than non- stutterers when writing numbers, letters, or symbols with the left hand (see Table 5). Finally, stutterers had more total mirror reversals and more reversals in left-hand writing than did non- stutterers. Results comparing righthanded and lefthanded subjects are summarized in Table 6. As indicated in Table 6, there were no 33 34 0A=000533 aomowv 22222222 222222222 usocuwz Aucm:_2 2222222222 2o compmpzopmo :0 22222 2222222 nowmqm 2202:22202m2 222.v2z 22.2 222.2 2.22 2.22 ---- ---- 2222222 222222 22222222222 222.v2z 22.2 222. 2.222 2.222 ---- ---- 2222 222222 22222222222 222.v 22.2 222.2 22.22 222.v2z 22.2 222. ---- ---- 2.22 2.22 22222.2 222222 22222222222 222.v2z 22.2 222. ---- ---- 2.222 2.222 2222 222222 22222222222 2 22 22222 2 2222222222 22222222222 2222222222222 2222222222 222222 xmmpu—mzu o2 gowgav sommam 2222222 mgmupaumcoz 2:2 memcmuuapm 2222222222 222 22222 :2 222m 222 2222222 gummqm N mFDMF 35 222.v2z 22.2 22.2 2.22 2.22 ---- ---- 2222222 2222222 2222 222.v2z 22.2 22.2 222 222 ---- ---- 2222 2222222 2222 222.v2z 22.2 222. ---- ---- 22 2.22 2222222 2222222 2222 222.V2z 22.2 222. ---- ---- 2.222 222 2222 222222 2222 2 22 22222 2 2222222222 22222222222 2222222222222 2222222222 222222 222212222 o2 gowgav 222222 2222222 2222222222202 222 2222222222 2222222222 222 22222 :2 2222 2:2 2222222 commqm m wpnmh 36 222.v2z 22.2 22.2 222 2.22 ---- ---- 2222222 2222222 222.v2z 22.2 22.2 2.222 222 ---- ---- 2222 2222222 222.v2z 22.2 222. ---- ---- 222 2.22 2222222 2222222 222.v2z 22.2 222. ---- ---- 222 2.222 2222 2222222 2 22 22222 2 2222222222 22222222222 2222222222222 2222222222 222222 2222:2222 22 222222 222222 2222222 2222222222222 222 2222222222 2222222222 222 22222 :2 2222 222 2222222 222222 2 2222» 37 Table 5 Pretest Mean Scores for Bimanual Handwriting Organization in Stutterers and Nonstutterers (high score = high organization with maximum of 10 and reversal means refer to absolute values) Stutterers Nonstutterers F(l,36) P TaSk (n=20) (n=20) Greiner Numbers: 8.55 7.48 57.50 .0005 Right Hand Harris Numbers: 9.07 7.03 94.55 .0005 Right Hand Letters: 8.47 6.96 79.26 .0005 Right Hand Symbols: 8.75 8.37 4.06 NS Right Hand Greiner Numbers: 7.07 8.5l 28.35 .0005 Left Hand Harris Numbers: 6.38 8.99 46.90 .0005 Left Hand Letters: 6.89 8.4l 34.43 .0005 Left Hand Symbols: 8.37 8.83 4.60 .039 Left Hand . . Total Reversals l5.70 .80 77.35 .0005 Total Reversals .70 .80 .04 NS Right Hand Total Reversals l5.00 0.00 115.96 .0005 Left Hand 38 Table 6 Pretest Mean Scores for Bimanual Handwriting Organization in Righthanders and Lefthanders (high score = high organization with maximum of 10 and reversal means refer to absolute values) Task Stutterers Nonstutterers F(l,36) P (n=20) (n=20) Greiner Numbers: 8.31 3.26 .19 NS Right Hand Harris Numbers: 8.69 8.55 .72 NS Right Hand Letters: 7.70 8.22 2.84 NS Right Hand Symbols: 8.59 8.71 .52 NS Right Hand Greiner Numbers: 7.22 7.64 3.20 NS Left Hand Harris Numbers: 6.60 7.48 7.23 .010 Left Hand Letters: 6.97 7.59 7.80 .008 Left Hand Symbols: 8.49 8.47 .01 NS Left Hand Total Reversals 2.50 14.00 45.62 .0005 Total Reversals 1.00 .50 1.01 NS Right Hand Total Reversals 1.53 13.53 73.48 .0005 Left Hand 39 differences between righthanded and lefthanded subjects when writing numbers, letters, or symbols with the right hand. However, there were differences when writing numbers (Harris number list) and letters with the left hand. Handedness also was related to the number of reversals. Lefthanded subjects had more reversals and reversals when using the left hand than did righthanded subjects (see Table 3). Analysis of the means in Table 7 indicated that most reversals (F (1,36)=59.24, p<.0005) and reversals written with the left hand (F (1,36)=73.48, p<.0005) were made by lefthanded stutterers. In fact, only one nonstutterer had any reversals at all and these occurred when writing with the right hand. Concurrent Measures: Speech and Unimanual Sequential Tappipg, Multidimensional relationships were found between speech and sequential finger tapping (see Figure 2 and Table 8). Speech fluency and rate loaded one dimension directly related to total and correct sequential finger tapping and were not related to the type of sequen- cing error. The number of sequencing errors was inversely related to finger sequencing performance. As indicated in Table 9, the concurrent measures did produce more dysfluency in stutterers than in nonstutterers across all speech tasks (F (l,36)=5.66, p<.023) and spontaneous speech accounted for most of this difference (F (2,72)=4.72, p<.015). Across the 4 timeblocks involved in this study, spontaneous speech was most dysfluent, followed by oral reading, then singing (see Table 10 and Figure 3; F(6,216)=3.43, p<.003). Post hoc analysis 40 Table 7 Means Comparing Righthanded and Lefthanded Stutterers and Nonstutterers on Mirror-Image Reversals During Bimanual Handwriting Stutterers Nonstutterers Right Handed Left Handed Right Handed Left Handed Total Reversals 3.47 28.0 1.6 0.0 Reversals 3.06 27.0 0.0 0.0 Left Hand Reversals .40 1.0 1.6 0.0 Right Hand 41 Correct Speech Unimanual Fluency Sequencing ,4 +41 \e + + 1‘ " Speech Total Rate Tapping *=9l *=69 -26 +5 Finger 3 Omissions + Total Omissions *=85 zomm pzmgmm :Hmz Hahm fi mm 1 nm awe inc +84 jmv we [9141 Jad Bugddel ueaN .o weamwm 51 .ucc; new? vcc pcmwc asp saw: acrunmu meucwacmm szcmswcz ucm guwmam ucmcczu icou mcwgzc mgmncm;umm_ vcm mcmucmcpcmwg :w mcwagmu Loan?» Fmvpcwzcmm szcmswcz powecoo .m mgzmwd ecu: 888— weeeeeeuceu 1 I424 ecu: u;o_e meeeeezuces u xxx; nee; bee. meeeeezo;m_g u Iszm ewe» eemue~*_eee> new; b;m_e meeeeeeuemwx u xxx“ wz_m o o o Gama zmam hzmqnm - SS 92: E: aim $8 9qu :5: I Imm.o I m.o rmm.o im~& T m.~ lm~.~ [914l/suotssimo 436u13 ueaw .o. eeamwe 56 .ucm; gem? new agave ecu cue: manamu pmwucmacmm szcmswcz new commam ucmcgzocoo mcwgsu mgwccngwwp ucm mcmucmspsmwg cw mgoggm cowmmwso gmmcwm 4o Lmnsac Fmpop .FP mesmwd 884: nee: Pdub h=u_g leg4l/suotssgwo 436013 ueaw 2353543 aim d $325sz I 57 of that found for finger omission errors. The lefthanders had signi- ficantly more addition errors with their left hand as compared to the right hand (see Figure 12), and the left hand of lefthanders pro- duced more addition errors than the left hand of righthanded subjects. 58 mam usmssso . e se mm; ms» sue: mswgseu peepsmzcmm Fessesws: use sum -sou mmflmuupwswumesuwmp use msmusespsmws sw msossm sowyeuue smmswe eo senses Peach ms_saep so; umm: use: hum; hIQHm w.o I to e; 19141/5u0131ppv Jafiulj ueaw .. 232$.th aim .. mseezsxezess aruutq .~_ ee=e_s DISCUSSION The only significant difference between stutterers and non- stutterers during pretest speech was that nonstutterers were more fluent during spontaneous speech. This fluency in nonstutterers relative to stutterers during pretest speech is based on exclusion of starters (e.g., "uh...") which contributed 6.2% "dysfluency” in nonstutterers. Dysfluency in stutterers was defined specifically as wholeword or partword repetitions or prolongations. Starters (e.g., "uh...") occurred rarely in the pretest spontaneous speech of stutterers. Nhen starters were present in stutterers, they alleviated persistent blocking behavior and initiated speech flow into the next phrase. In nonstutterers, the starters usually func- tioned as a pause in spontaneous formulation of speech. Significant differences between stutterers and nonstutterers during pretest bimanual handwriting can be separated into verbal (Greiner and Harris numbers and letters) and nonverbal (symbols) performance. During bimanual handwriting of verbal engrams, three findings differentiated stutterers from nonstutterers: 1) Greater differences occurred between performance of the right and left hand in stutterers than nonstutterers; 2) the left hand of stutterers had poorer organization than nonstutterers; and 3) the left hand of stutterers, especially in lefthanded stutterers, produced mirror- 59 60 writing of verbal engrams, whereas only one nonstutterer had mirror- writing. These three findings suggest that stutterers and nonstutterers differ in their nonspeech bimanual motor organization. The differ- ence confirms previous findings of relative clumsiness in the left hand of righthanded stutterers. This finding, in addition to the relative clumsiness of the left hand in lefthanded stutterers supports several theoretical positions addressed previously: 1) stuttering has etiology in the lack of motor lead control necessary for motor organization during verbal tasks, particularly in left- handed stutterers; 2) the left hand production of mirror-script during bilateral activation results from early impairment of the right hand/left hemisphere organization of language which produces interhemispheric mirror-image reversals of language engrams (Corballis & Beale, 1976); and 3) the early left hemisphere impairment renders the left hand as the language-representative, especially in left- hand-dominant stutterers. According to the pathological lefthanded- ness model, this right hemisphere/left hand combination may not be efficient for language, resulting in pathological lefthandedness, particularly in language-related tasks (Satz, 1972). There were no significant differences between stutterers and nonstutterers in right hand performance during bimanual handwriting of nonverbal symbols. However, the left hand of stutterers had poorer organization than nonstutterers. No differences occurred between stutterers and nonstutterers in production of mirror-image nonverbal engrams. 61 The finding of poorer nonverbal organization with the left hand in stutterers might be seen as a result of interference from imposed right hemisphere language function, which over time com- promises right hemisphere nonverbal representation (Moore and Haynes. 1980). According to the pathological handedness model, the one righthanded nonstutterer who shoed mirror-writing only with his right hand would have incurred early right hemisphere damage, when his natural hand preference was his left. This right hemisphere damage would not be associated with disturbed speech centers, however, as it would for the lefthanded stutterer. During the concurrent speech and unimanual sequencing aspect of this study, righthanded stutterers evidenced relative clumsiness in motor organization of the left hand, lending further support to the pathological handedness model. The left hand of righthanded stutterers had significantly depressed performance compared to the left hand of righthanded nonstutterers; however, this was true only for the spontaneous speech task. This relative clumsiness during simultaneous speech and nonspeech, or dual-task performance is com- parable to the clumsiness of simultaneous handwriting in that two cerebral motor centers are competing, with motor activity arising from hemispheres with compromised or limited cerebral space. This limitation is not apparent in less effortful and motorically demand- ing speech or motor tasks, such as singing or silent no-speech finger sequencing. 62 The limited space for motoric coordination in righthanded stutterers is inferred to be in the left hemisphere which then allocates more demand on the right hemisphere which may not be an efficient motor programmer. This transfer of motor programming to the right hemisphere hypothesis is supported by the Sussman & MacNeilage (1975) study which indicated lack of typical left hemi- sphere activity in speech production-like tasks. In addition, this relative clumsiness was only seen during speech tasks (spon- taneous) which require much more active speech centers in motor programming. The inference based on the Hick et al. (1975) model of mechanisms of lateralized and generalized effects, is that those cortical areas responsible for speech sequential motor and non- speech unimanual sequential motor tasks are sufficiently close to result in interference during simultaneous activation. From the present results we know spontaneous speech has the generalized effect of producing dysfluency in stutterers, whereas oral reading and sing- ing do not. We also know from the present results that the demands that concurrent tapping and spontaneous speech make on motor organization are lateralized to the left hand in stutterers, while spontaneous speech did not have lateralized effects on the left hand of nonstutterers. It is the specific sequencing characteristics of the motor task and the degree of activation required that produces relative disorganization in stutterers. Further evidence for the cortical overlap in function for speech sequencing and unimanual sequencing arises from the strong 63 positive (+41) relationship acorss all subjects in the multidimen— sional analysis. Because of the lateralized interference during spontaneous speech only, it is necessary to examine further the motor programming differences between propositional and approposi- tional speech. In a recent study of levels of processing in speech produc- tion, Aldridge (1981) hypothesized two-level processing, with a central level requiring organizational mechanisms also required for rehearsal of information in short-term memory (as would occur in spontaneous speech) and a more peripheral execution-controlling level that places little demand on the central phonetic-organizational process. The central-level processes involve mechanisms for program- ming articulatory gestures with the peripheral mechanisms executing these phonetic programs. Aldridge suggests that if motor movements (speech or unimanual sequencing) can be accurately made in the absence of feedback, the inference can be made that the movement is programmed in advance, with the execution being ballistic and inde- pendent of feedback. In the present study unimanual finger sequen- cing is an example of movement programmed in advance with the sequen- cing activity being accomplished without visual guidance. Sequencing errors did occur however, in speech and unimanual sequencing. The speech movements most likely programmed in advance are singing and oral reading. Propositional, spontaneous formulation of speech probably demands activation of the central-organizational level process of speech production interfering with the ballistic automatic 64 movement of finger sequencing. Since the interference of spontaneous speech on finger sequencing occurred in stutterers' left hand, one might implicate difficulty in stutterers in amount of attention available for allocation to these competing programs (i.e., spon- taneous speech and left hand sequencing). Another way of describing the ballistic or automatic execution level of speech production is that it has reduced attentional requirements. Propositional speech requires short-term memory and attention. Whereas the right hand of stutterers has sufficient program to sequence accurately, the left hand does not and is therefore more disrupted because of the need to compete with the central-organizational level process involved with formulating speech. Following the Hicks et a1. (1975) model of mechanisms of lateralized effects resulting from cortical overlap in function, one could suggest that the decrease in left hand correct sequencing in lefthanders (but not righthanders) only during oral reading and singing would indicate right hemisphere representation of these speech tasks, but not of speech associated with spontaneous formu- lation. Therefore, it is important in future studies of hemispheric representation of speech in lefthanders and righthanders to specify type of vocalization being represented. Spontaneous speech relies more on the hemisphere responsible for temporal motor programming whereas oral reading relies more on hemispheric representation of the written language and perceptual processing of the reading passage. In this study, the left hand of lefthanded stutterers and non- stutterers was interfered with less than was the right hand during 65 spontaneous speech, indicating left hemisphere/right hand temporal programming to be relatively disorganized in lefthanders. This might also be interpreted as a result of greater right hemisphere repre- sentation of motor programming in lefthanders, especially in left- handed stutterers as compared to righthanded stutterers and non- stutterers. By examining the relative dysfluency in righthanders and lefthanders, the assumption can be made that lefthanders have more effective bilateral representation of speech motor programs. During the concurrent performance tasks, all righthanders, whether stutterers or nonstutterers, were more dysfluent while sequentially tapping with their right hand than were lefthanders while tapping with their right hand. This finding gives further support to left hemisphere representation of speech in right handers. The Hicks et al. (1975) model of mechanisms of lateralized effects during concurrent speech and nonspeech tasks presupposes interference on all motor activity. I have discussed interference on speech resulting in dysfluency and I can also discuss interference on sequential finger tapping, in addition to general correct sequencing, by discussing the type of sequencing errors in tapping. The multidimensional relationships in the analysis, indicate an inverse relationship (-26) between type of finger sequencing error and correct unimanual sequencing performance, and no relationship to speech performance. Within the unimanual sequencing performance, the type of error could be related to hemisphere activity especially in lefthanders. If there is a relationship, it arises from the fact 66 that finger omission errors in lefthanders originate from the left hemisphere and finger addition errors originate from the right hemisphere. In righthanders, there was no difference between right and left hand performance in the number of finger omissions or additions. Further research into signal detection and false alarm responding within the unimanual sequential procedure is warranted. One might assume finger omissions arise from lack of efficient motor programming during interference of concurrent speech and unimanual sequencing, and the finger additions in the left hand of lefthanders resulting from an impulsive or overly active pro- grammer in the right hemisphere. APPENDICES 67 APPENDIX A Verbal and Nonverbal Stimuli for Bimanual Simultaneous Handwriting; Numbers, Letters and Symbols 68 23 ab 36 hd , 75 10 11 12 789 1.2.3456 APPENDIX 8 Project Description Letter, Research Informed Consent Form, Individual Information Form, Sequential Finger Tapping Complete Instructions 73 74 MICHIGAN STATE UNIVERSITY DEVELOPMENTAL PSYCHOBIOLOGY LABORATORY Speech Development Project Department of Psychology, Snyder Hall East Lansing, Michigan 48824 PROJECT DESCRIPTION LETTER Investigators in the Developmental Psychobiology Laboratory at Michigan State University are conducting a long term scientific study of the relationship between behavioral and emotional aspects of stuttering. As a participant in the present study, you will complete question- naires concerning feelings about speaking situations, reactions to various experiences, and degree of speech fluency. The final aspect of this experiment will assess handedness and lateral hand organiza- tion during speech. As a participant, you will read aloud, spon- taneously speak and sing while tapping with your fingers in sequence. This letter is to inquire whether I may give your name to these investigators so that they or a member of their staff may contact you to discuss your participation in their study. I would like to add that in no way can any individual be identified once the informa- tion is collected. Strict confidence and anonymity are guaranteed by removing all names and identifying materials from records that are kept. I would also like to emphasize that this research does not involve therapeutic intervention. This is a basic research effort which may prove useful for therapists and researchers and may have implications for therapy. Should you agree to consider participating in this work, I will forward your name to the project staff. What will happen next is that they will contact you and arrange an interview to discuss study participation in greater detail. It is anticipated that the research project will require one 60-minute session and will be conducted on the campue of Michigan State University. 75 If you want to consider participating in this work, please sign the attached form so that I may inform the study workers. Signing this form does not obligate you in any way should you decide not to participate. Also, although I hope that you will decide otherwise, please indicate on the attached form if you do not wish to be con- tacted. Finally, if you have any questions about this letter you may discuss the project with one of the project staff by calling 353-6468 or 353-3933. Jay Greiner Project Coordinator Hiram E. Fitzgerald Lauren J. Harris Paul A. Cooke Professor Professor Assistant Professor Dept. of Psychology Dept. of Psychology Audiology & Speech Sciences Please check one of the following: Yes, I give my permission to release my name and phone number so that the above named investigators may contact me to pro- vide more detail about their experiments. No, I do not want to have my name released nor do I wish to participate in the project described on the enclosure. Signature Name: please print Date Phone number Please return this form in the self-addressed, stamped envelope. Thank you. 76 MICHIGAN STATE UNIVERSITY DEVELOPMENTAL PSYCHOBIOLOGY LABORATORY Speech Development Project Department of Psychology. Snyder Hall East Lansing, Michigan 48824 RESEARCH CONSENT FORM I have freely consented to take part in a scientific study being conducted by Jay Greiner (Research Assistant), Hiram E. Fitzgerald and Lauren J. Harris (Psychology), and Paul A. Cooke (Audiology and Speech Sciences) all of Michigan State University. The study has been explained to me and I understand the explanation that has been given and what my participation will involve. I understant that I am free to discontinue my participation in the study at any time without penalty. I understand that the results of the study will be treated in strict confidence and that I will remain anonymous. Within these restric- tions I understand that general results may be presented at pro- fessional and scientific meetings and may appear in appropriate professional journals and other publications. Moreover, the results of the study will be made available to me at my request. I understand that my participation in the study does not guarantee any beneficial results to me directly. Finally, I understand that, at my request, I can receive additional explanation of the study after my participation is completed and that I will not receive any financial compensation for participation in this one-hour study. Signed: Parental Signature (if necessary): Date: Note: This form is to be held in locked file. 77 MICHIGAN STATE UNIVERSITY DEVELOPMENTAL PSYCHOBIOLOGY LABORATORY Speech Development Project Department of Psychology, Snyder Hall East Lansing, Michigan 48824 INDIVIDUAL INFORMATION This information is to be kept in the locked file folder and used to l) assign code numbers, and 2) provide research summaries to parti- cipants. Participant: Name: Phone Number: Address: I would like to receive summaries of the research results when they are available. YES NO CODE NUMBER 78 INSTRUCTIONS Condition A: L,R/L,R/R,L/R,L Practice Trials First I'd like you to practice tapping with your left hand. When you tap, always begin with your index finger (point to it) and move outward to your small finger. (Demonstrate.) When you tap With your small finger, return to your index finger and begin a new sequence. 00 not tap with your thumb. Be sure to press each key in sequence. OK, now do that as fast as you can with your left hand. Next I'd like you to practice the same thing with your right hand, always being sure to tap in sequence from index finger outward to small finger then return to index finger. Do not tap with your thumb. OK, now do that as fast as you can. Now, when the experiment begins you will notice the left thumb light will be on. Whenever a light is shining on the board, you do nothing. When the left thumb light goes off, begin tapping as we practiced with your left hand. You will continue tapping with your left hand until the right thumb light comes on. Again, when a light is on, do nothing. Nhen the right thumb light goes off, begin tapping with your right hand. Continue tapping with the right hand until the left light comes on. When the left thumb light goes off, begin tapping with the left hand. During the 20 minutes of the experiment, we will continue to switch back and forth from left to right hand. There will be a 30 sec. rest period three different times throughout the experiment. I will be here to tell you when each rest period occurs. 79 Condition A (Continued) There are four parts to the tapping task. In each part you will do different things. First, you will be tapping with the left and right hand as fast as you can while remaining silent. Second, when you are tapping, you will be reading outloud from this passage. When you tap with left hand, you will read the first paragraph and when you tap with your right hand you will read the second paragraph. Third, I will ask you to tell me in sentences what comes to mind about a particular word that I might mention while you tap with your left hand and then your right hand. Fourth, while you tap with your left hand I'd like you to sing "Row Row Row Your Boat" and continue singing until you finish tapping with the left hand. Then sing the same song while you tap with the right hand. Throughout the experiment, the order in which you read, talk or sing with vary. I will tell you what you are to do in each part of the task. OK? Are there are questions? The first thing that will happen is the left thumb light will come on. When that light goes off, begin tapping with your left hand and I will tell you what to do next. OK? 80 INSTRUCTIONS Condition 8: R,L/R,L/L,R/L,R Practice Trials First, I'd like you to practice tapping with your right hand. When you tap, always begin with your index finger (point to it) and move outward to your small finger (demonstrate). When you tap with your small finger, return to your index finger and begin a new sequence. 00 not tap with your thumb. Be sure to press each key in sequence. OK, now do that as fast as you can with your right hand. Next I'd like you to practice the same thing with your left hand, always being sure to tap in sequence from index finger outward to small finger then return to index finger. Do not tap with your thumb. OK, now do that as fast as you can. Now, when the experimenter begins you will notice the right thumb lights will be on. Whenever a light is shining on the board, you do nothing. When the right thumb light goes off, begin tapping as we practiced with your right hand. You will continue tapping with your right hand until the left thumb light comes on. Again when a light is on, do nothing. When the left thumb light goes off, begin tapping with your left hand. Continue tapping with left hand until the right light comes on. When right thumb light goes off, begin tapping with the right hand. During the 20 minutes of the experiment, we will continue to switch back and forth from right to left hand. There will be a 30 sec. rest period three different times 81 throughout the experiment. I will be here to tell when each rest period occurs. There are four parts to the tapping task. In each part you will do different things. First, you will be tapping with the right and left hand as fast as you can while remaining silent. Second, when you are tapping, you will be reading outloud from this passage. When you tap with right hand, you will read the first paragraph and when you tap with yourileft hand you will read the second paragraph. Third, I will ask you to tell me in sentences what comes to mind about a particular word that I mention while you tap with your right hand and then your left hand. Fourth, while you tap with your right hand I'd like you to sing "Row Row Row Your Boat" and continue singing until you finish tapping with the right hand. Then sing the same song while you tap with the left hand. Throughout the experiment, the order in which you read, talk or sing will vary. I will tell you what you are to do in each part of the task. OK? Are there any questions? The first thing that will happen is the right thumb light will come on. 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