b 5‘ ‘1' ; ‘51.. "l-‘J‘lblx ‘ 7"“ 'i ? . “3mm h 9:§I¢,‘ ‘o' .. t . h’ ‘-'-3£31\u'-.-.. 344.1 24;, 8:." is: .' 2p .5 13-..- _!L.,,: £3: 03 '5 a). T9 0" ‘ £3 :‘7. “S 33‘? y... a L 31,1? G" u. I. .7 I & 2“________‘_____:__::__:__ mm v . n O t ~' (:93: s: 7" fi‘r g: 1.3; - o . .t ( 1"!“ ‘36. ; Q: '5“? V. 3 r0““ up.“ ”.0: w. ’ ‘ ‘- 1‘ V .— .6 4|. PLACE IN RETURN Box to remove this checkout from your record. TO AVOID FINE return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE moo mm“ ABSTRACT A STUDY OF THE EFFECTS OF MECHANICALLY INDUCED TENSION OF THE NECK MUSCLES ON THE PERCEPTION OF VERTICALITY by Carl W. Schneider The present study was designed to investigate the effect of increasing tension of the neck muscles on the perception of verticality. An apparatus was constructed that enabled the experimenter to produce a rotational torque on the subjects neck by the addition of weights. When the subject counteracted the force of the weight by main- taining a fixed position with the head, tension was induced in the neck muscles. Under the various degrees of tension the subject was required to set a rod to the vertical position from.some initial position. Four degrees of tension and seven initial rod positions were used. These were combined to form 28 conditions which were randomized and presented to each subject. The measure of the effect of tension was the number of degrees the subjecfls setting deviated from true vertical (0°). Thirty-five male subjects made one setting under each of the 28 conditions. Carl W. Schneider Specifically, the eXperiment was designed to test the hypotheses that as tension of the neck muscles increases the perceived vertical will deviate farther from the true vertical, and that the perceived vertical will still deviate from.the true vertical independent of the initial rod position. The eXperimental results support the first hypo- thesis and do not support the second. The relation- ship between neck tension and the subjects' deviation of setting from true vertical was found tobe prOpor- tional. Initial rod position did have an effect on the subjects' settings when the rod approached true vertical in a clockwise direction. One further finding of the eXperiment suggests that tension may produce a change in the curvature of the lens of the eye. Approved: S1V~Qqfl§ Date: EMA 15,1967“ A STUDY OF THE EFFECTS OF MECHANICALLY INDUCED TENSION OF THE NECK MUSCLES ON THE PERCEPTION OF VERTICALITY by Carl W. Schneider A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF.ARTS Department of Psychology 1962 ACKNOWLEDGMENTS The writer extends his sincere thanks to Dr. 8. Howard Bartley, chairman of the guidance committee, for his help in formulating the problem and for his interest and encouragement in bringing this effort to fruition. Thanks is also expressed to Dr. Donald Ml Johnson and Dr. Stanley Ratner for their reading and sugges- tions on the writing of the thesis. C. w. S. ii TABLE OF CONTENTS LIST OF TABLES.......................................1v LIST OF FIGURES...................................... V I INTRODUCTION.................................... 1 II METHOD..........................................lO Subjects.....................................10 Apparatus....................................lO Procedure....................................lu III RESULTS.........................................16 IV DISCUSSION......................................2u Further Check on Certain Results.............26 V SUMMARY.........................................28 BIBLIOGRAPHY.........................................30 111 TABLE 1 TABLE 2 TABLE 3 LIST OF TABLES Algebraic mean position of the perceived vertical with reference to the true vertical for all of the 28 conditions........................l7 Arithmetic mean position of the perceived vertical with reference to the true vertical for all of the 28 conditions........................18 Summary of Analysis of Variance of settings of the rod to verticality under the different conditions of tension and initial rod position.........20 iv Figure Figure Figure Figure h LIST OF FIGURES Apparatus...............................11 Cutaway of supporting base to show mounting of revolving mechanism.........12 Target..................................12 Graph of mean deviations of 35 subjects from true vertical for the 28 conditions arranged in order of presentation................22 INTRODUCTION The present study in its Specific form, stems from several considerations, some observational and some theoretical. The title ostensibly links neck tension and visual perception, the former as a con- dition for the latter. Gibson (h) for one, has pointed out that all visual reaponses we know about occur, not in a vacuum, but in a gravitational field, and the visual response is not something totally separate from concurrent responses via other mechanisms such as kinethesis. He believes up and down would have no meaning outside the gravitational field. ‘We are unaware of much of the work that has been done in the study of "weightlessness" at the present time because of military secrecy. Hence, the results of various tests of Gibson's theory that might have been incidentally made are unknown to us. The point to be made here, however, is that we know that the organism.does Operate in a gravitational field, and that various patterns of muscular tension do exist during perceptual activities. we presume the organism is some sort of a unity. Whereas we are not fully aware of the nature of the connections between various activities in the body, we tend to make certain assumptions, varying from.that we take as sure, to that we wish to test. The ideas that Werner and wapner (9) eXpress in their sensory-tonic theory of perception are an example 1 2 of connecting perceptual end results and various body tension conditions. While we need neither describe their theory here in detail nor follow it in our experi- mental planning, the fact of their ideas and the nature of some of their findings do lay a tenable foundation for assuming some active relationship between the struc- ture of the visual field (the pattern of the seen field) and muscular processes. The organism, as far as relation to gravity is con- cerned, involves two major components, (a) the head and (b) the trunk and hind limbs. Body posture, as far as support in the upright position is concerned, is carried out by the leg and back muscles. The visual organs, the eyes, are in the head which is variably related to the body in position. The vestibular organs are in the head as well. The neck muscles connect and control the postural relation of head and trunk. The only mode of feedback from muscle action is through the kinesthetic sense with its stretch afferents, etc. in muscle tendon and joint. Tension is one of the effects produced in muscles, either through their own contraction or through loads put upon them. Various positions involve both active tension and passive tension. One of the results of kinesthetic information is not only effective posture or movement, but also self-awareness of position and motion. This self-awareness occurs in relation to what is seen, and so arises the question of what interrelations 3 there may be between the two. Something may look to be where it is seen on account of some peculiar body posi- tion, or the body position may be experienced where it is by reason of how the visual field appears. To anti- cipate a bit in regard to the pr0posed problem, the following may be pointed out. For example, a subject is asked to adjust a rod to what would be a true verti- cal, and the result may depend not only upon body orien- tation in the gravitational field, but also upon where the starting position of the rod is. All experimental design, even in ignorance of this, is likely to include different rod starting positions just as a check on initial position as a possible effective variable. Various investigators have recognized the impor- tance of the neck in motor and perceptual processes. Bartley (l) and'Woodworth and Schlosberg (11) have sug- gested that the existing evidence shows that the neck muscles may be very important indicators of an overall state of muscular tension. Dusser de Barenne (3) has thoroughly analyzed the importantcfunctions performed by the neck muscles in aiding the organism to maintain its motor coordination. From his analysis the following conclusions are drawn. The head is a very heavy structure which must be sup- ported by the neck muscles. If the head is not sup- ported the organism.cannot maintain a prOper sense of *n—w "- equilibrium. The head contains the visual mechanism. h which is the most important distance receptor. There- fore, movement of the head and eyes to locate an object in space or in anticipation of body movement must be accomplished with extreme ease or motor coordination is disturbed. It is reported in Guyton (S) that the neck prOprio- ceptors yield the most important information needed by the organism.in the maintainance of equilibrium, because they keep the nervous system informed of the orientation of the head with respect to the rest of the body. ‘When the head is tilted to one side the neck prOprioceptors oppose impulses from the vestibular apparatus and thus prevent the person from develOping a sense of mal- equilibrium. Cohen (2) performed a study to investigate the.role of the neck prOprioceptive mechanisms in body orienta-- tion and motor coordination. Macaque Nemestrina monkeys and Papio papio baboons received injections of an anes- thetic to the Cl, 2, 3 dorsal roots. This injection blocked the passage of impulses from the neck prOprio- ceptors to the central nervous system. As a result of this blocking the animals became severely impaired in motor coordination and space orientation. A very limited number of experiments have been designed to study the effects of muscular tension of the neck upon visual perception. Some that hgve involved the neck muscles were not directly interested 5 in the importance of this area as such. The findings are reported here because it is felt by the eXperimenter that part of the results are pertinent to this study. In 1937 Kleint (6) found that when subjects, observing a vertical line, sit erect and counterbalance a weight attached to the head, the vertical line tends to appear tilted in the direction of increased tonus. Werner and wapner (10) did a study in which the subjects received electrical stimulation to the left or right side of the neck. After the stimulation began, the subject was required to set a luminescent rod to the vertical position from an initial position of 30° to the left or right of vertical. They found that the mean control setting (no extraneous stimulation) was -l.Lto (counterclockwise from true vertical). When stimulation was applied to the right side of the neck the setting was to the left of control, and when stimu- lation was applied to the left side of the neck the setting was to the right of the control. The settings under stimulation.were significantly different than the control settings. Starting position of the rod was not tested for effect. In a later paper, in which Werner and'Wapner (9) were develOping their sensory-tonic theory, they reported the following on the previous study. The control was reported to be +l.h°. When stimulation was applied to the right side of the neck the setting was to the right 6 of control, and when the stimulation was applied to the left side of the neck the setting was to the left of control. This report seems to contradict the findings of the eXperiment. Therefore, it seems that the only finding from the study we can be sure of is that extra- neous stimulation does have some effect on the setting of a rod to the vertical position. In another study Werner and Wapner (8) investi- gated the effects of sidewise tilt of the head on the perception of verticality. Three starting positions of the rod were used.(+30°, 0°, -30°). The control (head upright) was found to be -1.0° for men and -l.u° for women. When the head was tilted 15° to the right the settings were to the left of control, and when the head was tilted hSo to the left the settings were to the right of control. They found that the head tilt had a significant effect, but the starting position of the rod did not. In light of the foregoing discussions, it can be seen that one may wish to study the matter of muscle tension patterns in relation to some function of the visual field, verticality of an object in it, for example. What we have said suggests the neck-muscle tension would seem.to be a significant case to study. Already some study has been made of the effect of neck-muscle tension by using head tilt as a variable. This procedure involves not only the production of the desired asymmetry 7 of muscle tension on the two sides of the neck, but also it involves departure from.the primary head positions, i.e. head upright and in line with the target and/or the gravitational axis. In other words, head tilt may introduce factors that are both unnecessary and inappro- priate for the fundamental testing of the prOposition suggested. A preferable set of conditions productive of left- right asymmetry in neck-muscle tension would include some device for simply applying a rotational torque to the head while the subject is asked to maintain a fixed straight ahead position. Thus, what we are asking is simply the application of a rotational tension without head rotation. The question is whether the appearance of any factors of the visual field will be modified by this. One of the simplest visual tasks is the adjustment of a rod, rotatable around its midpoint in the frontal plane, so that it appears to be in the true vertical. Actually, the organism tacitly Operates on certain pre- mises, namely that it is either in line with the gravi- tational vertical or that it is a "known" amount out of line. This is simply to say it uses something as a base, for "looking vertical" is not a characteristic of visual appearance independent of everything else. In the pre- sent experiment the subject is in every respect in line with the true vertical, but asymmetrical tension is 8 produced in the neck. This tension is not of the kind produced by head tilt or other deviations from the true vertical. It is the kind produced by horizontal torque, the pattern most dissimilar from the gravitational. The question then is whether this tension will produce some effect in the apparent vertical. If so, then one of the strongest arguments for general and broad rela- tions between kinethesis and Space perception has been demonstrated. The present study was designed to investigate the effects of tension of the neck muscles upon the percep- tion of verticality. The Specific hypotheses to be tested are: a. As tension of the neck muscles is increased the perceived vertical will deviate further from the true vertical (plumb line). b. That the perceived vertical will deviate from the true vertical independent of the initial rod position. While the foregoing hypotheses give Specific character to what is literally eXpected, the essen- tial question is whether or not neck tension has some sort of influence upon the perception of the visual field. 'Were there no influence whatsoever detected, then the answer would be negative and the matter would be terminated. On the contrary, if some sort of dependable relation is demonstrated, 9 then an essential sort of success has been attained. What is to be said or done further depends upon what relations are found. In.a way this involves a second step and can easily carry one beyond the natural bounds of the present investigation. METHOD SUBJECTS: The Ss in this experiment were 35 male stu- dents from an introductory course in psychology. The 83 were volunteers and none had participated in a psy- chological eXperiment previous to this one. They ranged in age from 18 to 28 years. None of the Ss had any Specific knowledge about the purpose of the eXperiment. APPARATUS: An apparatus was designed to induce tension in the muscles of the neck. A rotational force to the S's right was applied to the head in the horizontal plane, and when the S counteracted this force, tension was induced in the neck muscles. The whole apparatus is illustrated in Figure l. The main part of the revolving mechanism.was supported by a rigid steel pipe stanchion, 72 inches high, ES inches wide and 26 inches deep. The revolving mechanism is illustrated in Figure 2. The base supporting the revolving disk was 37 inches long, 22 inches wide and 1% inches thick. In the center of the base there was a hole 16 inches in diameter with a counterbore 18 inches in diameter and 3/h inch deep. The counterbore provided a 1 inch track on which the disk revolved. The revolving section contained a ply- wood disk 15% inches in diameter and 3/h inch thick. Another disk, 12% inches in diameter and 1% inches thick, was centered on the larger disk. Six Killian wheel bearings with 3% inches X 3/8 inch set screws for axles lO 11 Figure l Apparatus 12 Figure 2 Cutaway of supporting base to show mounting of revolving mechanism 0. . 4 +qo -&0 Front Back Figure 3 Target 13 were attached equidistantly around the circumference on the t0p of the larger disk, and the disk revolved freely on the track. Four of the Killian hearings were also used to keep the mechanism centered as it revolved. Two steel attachments, 10 inches apart and parallel, projected down 8 inches from the underside of the 12% inch disk. These attachments held the foam rubber-lined head strap. A chain.was attached to the right edge of the disk and run over the back left side of the stan- chion on a pulley. When weights were attached to the chain the disk turned to the S's right. An adjustable stool rested on a platform (5 inches high) directly below the head strap. An electrical switch that con- trolled a light projector was suSpended on the left side of the S within his reach. The visual target was 18 feet from the S's head attachment. It consisted of a white rod, 2h inches long and 1 inch in diameter, which revolved about its mid- point in the center of a black screen, 36 inches Square. On the reverse side of the screen from the rod a wheel containing a dial indicated the degree in which the rod was placed. The rod revolved in a lighted area 2 feet in diameter. The mechanism was constructed so that the rod could be moved very slowly and smoothly. The pro- tractor used allowed accurate readings to be made within o.25°. Both the dial and the rod were set to plumb line vertical (0°). The target is illustrated in Figure 3. Illlllll'lallll‘iirl. 11; During the entire experiment the room.was dark and only the illuminated rod could be seen. PROCEDURE: Each subject was met at the door of the experimental room.which was completely dark. The S was then seated in the apparatus for a period of ten minutes to allow some time for dark adaptation. During this time E obtained information from the S about his height, weight, neck size, agd and class. Before the experiment began each S received the following instructions: “You are about to participate in an eXperi- ment designed to study the effects of tension of the neck muscles on the setting of a rod to the vertical position. A foam.rubber-lined belt will be strapped around the t0p of your head, and during the experiment you will feel this belt pulling your head in a clockwise direction. You must counteract this force by keeping your head directly to the front at all times. When I give you a signal you will push the switch in your hand to turn on the projector. At this time the rod.will move slowly from some position toward the vertical. When you think the vertical point has been reached say 'StOp'. If the rod still appears as though it is not vertical you will have some time to make finer adjustments in either direc- tion. 'When you are satisfied.with the vertical setting turn off the projector. Please do not talk during the experiment unless you have some question about procedure. All other questions about the eXperiment will be answered at the end of the experiment." After the instructionswere completed the S was given a switch which controlled the light projector and was then given four practice trials with no tension and the starting position of the rod in h different positions. At this point E answered any questions about procedure. 15 After the practice trials each S was required to make one setting under each of 28 different conditions. There were four degrees of tension: 0 (control), 1 (appa- ratus strapped on), 2 (2.7 Kg weight added), 3 (h.h Kg weight added). There were seven different rod starting positions: 0°, +50, -5°, +300, -3o°, +9o°, and -9o°. All of the starting positions were combined.with the h degrees of tension to make a total of 28 different conditions. The 28 conditions were randomized and presen- ted to each S in that order. The S had approximately 20 seconds to make his setting, and there were 30 seconds between the end of one setting and the beginning of the next. During this time E changes the weight condition on the apparatus. The measures were degrees of deviation from.true (plumb line) vertical. If the deviation was clockwise of true vertical it was arbritrarily designated as (+) positive, and if the deviation was counterclockwise of true vertical it was given a (-) negative Sign. Each setting that the S made was recorded on a data sheet by E, and S had no knowledge of his results. RESULTS Table 1 shows the algebraic means obtained by the 35 SS on each of the 28 conditions. As can be seen from the table, without tension (control), the perceived vertical is +.lO7°. That is, the rod is perceived as verticaL,on the average when it is rotated .lO7° clock- wise. Also the grand means for the four degrees of ten- sion indicate that the perceived vertical tends to deviate farther from the true vertical as the tension is increased. Tension and deviation from true vertical are almost prOportional. However, the grand means for the various starting positions of the rod do not Show the same type of relationship. The perceived vertical for the (+) starting positions deviate farther from true vertical than that for the (-) starting positions. This relationship is consistent for each of the three (+) and three (-) starting positions. That is, the grand means for +50, +300, and.+90° are larger than those for -5°, -3o°, and -9o°, respectively. This indi- cates that the rod starting position did influence the setting. Table 2 presents the arithmetic means obtained by the 35 SS on each of the 28 conditions. In other words, the signs have been ignored in computing the totals and the means. The observed mean for each condition indi- cates that the 3's deviation from the true vertical becomes more extreme as tension increases. The most 16 17 TABLE 1 Algebraic mean position of the perceived vertical with reference to the true vertical for all of the 28 conditions Tension Initial Rod Grand Position 0 l 2 3 Mean 0° .021 .035 .078 .071 .051 +5° .257 .385 .978 .900 .630 -5° -.2h2 -.392 .171 -.107 -.1h2 +300 .050 .321 .u28 .650 .362 ~30° .2oo .1u2 .1lh .228 .171 +9o° .292 .307 .657 .828 .521 -90° .171 .235 .207 .h85 .h90 Grand.Mean .107 .1h7 .376 .h36 18 TABLE 2 Arithmetic mean position of the perceived vertical with reference to the true vertical for all of the 28 conditions Tension Initial Rod Grand Position 0 l 2 3 Mean 0° .292 .250 .335 .357 .309 +5° .700 .828 1.192 1.31h 1.009 -5° .728 .850 .8111 1.135 .882 +30° .86h 1.035 .828 1.307 1.009 -30° .671 1.100 1.11u 1.h00 1.071 +90° .721 1.035 1.057 1.h71 1.071 -90° 1.01h .992 1.107 l.h7l 1.1h6 Grand Mean .713 .870 .921 1.208 l9 extreme deviation from true vertical occurs with the greatest degree of tension and the most extreme rod position. .Many SS consistently perceived the vertical to be to the right of the true vertical (0°), and there are some that perceive it to be to the left. However, on the average, there seem to be more SS that perceive verticality clockwise of the true vertical. The data from the experiment were analyzed by a triple classification analysis of variance and a summary of the results is presented in Table 3 (7). It is ‘ assumed here that error of measurement variance is the same for all cubicles. There is no measurement repli- cation with m scores per cubicle so the assumption is not testable (7). [As can be seen, the statistical analysis of the data is in line with the obtained mean values. As tension increased the perceived vertical deviated further from the true vertical. The effect of tension was significant, F = 15.89, df = 3 and 102, p