EARLY EXPERIENCE AND
AVOEDANCE BEHAVIOR:

SCME RELEVANT PARAMETERS

“zest: for {the Dayna of M. A.
MECHE‘SAN HEW WWEESETY
Norman J. Karl

E965

IHESlS

 

[J LIBRARY

Michlgan State
Universuy

     

ROOM USE 0*»va

ABSTRACT

EARLY EXPERIENCE AND AVOIDANCE BEHAVIOR:
SOME RELEVANT PARAMETERS

by Norman J. Karl

The present study investigates the influence of per—
ceptual experience, litter background and species differ—
ences on avoidance behavior and body weight.

Vauipulation of perceptual experience consisted of
placing an animal in a highly reduced perceptual input
{EPI) environment (i.e., darkness, masked sound, and
visual isolation from other animals). It was introduced
at one of three times of age: viz., just after weaning
for 87 days (Early RPI), the 37 days just before testing
began (Late RPI), and just after meaning for Fm ohys
(Extended RPI). A control group remained in :kr dyer
laboratory for 5H days after weaning.

Eight P. leucopus and eight P. policnotus mothers
casting a minimum of four pups each supplied the total
sample of 6M §s. Each pup from the same biological m~irtl
was randomly assigned to one of the three exterimental
ditions or to the control group. Each gr up cgnsisted ml

a total of 16 animals, eight from each of the two spevies.

Norman J. Karl

In testing for effects on later avoidance behavior,
measures were taken of the time required for discovery of
water in a novel setting, reactivity to shock, and rapidity
of avoidance conditioning and extinction. A punishment
procedure was employed by means of which an aversive shock
stimulus was coupled with a consummatory drinking response.
Testing was begun for an § when it had reached maturity,
and continued until he had successfully learned to avoid
the aversive stimulation, and then had subsequently come
to extinguish this avoidant behavior in the absence of
shock. Body weight was determined throughout testing.

The results clearly indicate that whether or not RPI
has an effect on avoidance behaVior, as well as what the
direction of the effect will be, depends upon both the
species of the animal and the particular behavior being
looked at. Since there is no general systematic effect
associated with the EFT treatment dimension, it was con—
cluded that diminished sensory input per_§e during the
early life of an organism does not permanently effect per—
formance in terms of reacting to noxious or novel stimu—
lation, learning to avoid an aversive stimulus, or extin—
guishing avoidance behavior.

Both litter background and species differences occur
on almost all measures. The importance of these factors

is emphasized since frequently the experimental literature

Norman J. Karl

fails to report adequate controls for these variables. It
is proposed that many previous results which find in favor
of, or against, the "effects of early experience" may be
spuriously derived due to the use of litters from just a
few mothers, or a strain of one type.

In general the findings do not lend support to the
so-called Hebbian position that an animal reared under a
reduced sensory environment will be more retarded at
maturity in the ability to learn, and to reSpond to aver—
sive stimulation, than will animals not so deprived.
Neither do the results support another major theoretical
formulation which posits that the early environmental
situation, where stressful, will yield a mature organism
that is better adapted to cope with his environment, or
one that is more reactive to a later stressful situation.

On the basis of present and previous results, it
seems clear that there are many factors which are inter—
dependent and serve to influence the effects of early RPI
on later behavior. Such factors as the measuring device,
the environment (housing) of the §s, sex, age, and Species
need to be considered in the interpretation and generaliza—

tion of any particular set of results.

fl f/Zfl‘WMQ/
floatyly/ ”a,

EARLY EXPERIENCE AND AVOIDANCE BEHAVIOR:

SOME RELEVANT PARAMETERS

BY

Norman J. Karl

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF ARTS

Department of Psychology

1965

ACKNOWLEDGMENTS

The author wishes to express his appreciation to
Dr. R. E. McMichael, master's committee chairman, for his
very thoughtful consideration and help on this project,
and throughout the entire graduate program. Dr. J. A.
King, offered highly valued constructive criticism and
suggestions, and was kind enough to supply the animals,
cages, and water bottles used in the study.

The author is also indebted to Dr. C. Hanley and
Edwin Rubel for their suggestions on the statistical
analysis. A very Special word of thanks goes to the
author's wife for her constant support and encouragement

'througtmnft this tmnaiod.

ii

DEDICATION

To Elly

iii

TABLE OF CONTENTS

ACKNOWLEDGMENTS

DEDICATION

LIST OF TABLES.

LIST OF FIGURES

Chapter
I. INTRODUCTION: LITERATURE REVIEW
II. PROBLEM
III. METHOD
Subjects. . . . . . . . . . .
Weaning, Marking, and Sex Determination
Caging and Maintenance Activities
RPI Conditions. . . . . . . . .
Testing Apparatus, Procedures, and Measures
IV. RESULTS
Treatment Effects.
Species Effects .
Litter-Mate Effects
Sex Differences
V. DISCUSSION.
VI. SUMMARY.
BIBLIOGRAPHY
APPENDICES

iv

Page
ii

iii

vi

KC)

11

13
i6

17

.J'
L..1_.

27
29

Table

1.

LIST OF TABLES

Schematic Representation of Subject Assign-
ment--Peromyscus leucopus and Peromyscus
polionotus . . . . . . . . . .

Distribution of Male and Female Subjects by
Treatment and Condition . . .

F. and p Values for Response and Body Weight
Measures . . . . . . . . .

Mean SFT Scores (in milliamps) for SS Grouped
by Species and Treatment. . . . . . ..

Mean ITD Scores (in seconds) for SS Grouped by
Species and Treatment . . . . . . .

Mean TC Scores for Ss Grouped by Species and
Treatment. . . . . . .

Mean Response and Body Weight Values for P.
leucopus and P. polionotus .= . . . . .

Means of the Four Pups from the Same Biological

Mother on Each Measure

Page

lO

13

23

2A

26

26

28

3O

Figure

1.

LIST OF FIGURES

Mean Values of First Shock Taken for Species
and Treatment Conditions . . . .

vi

Page

25

CHAPTER I
INTRODUCTION: LITERATURE REVIEW

Psychoanalysis and the comparative studies of primitive
cultures have provided evidence emphasizing the importance
of early experience on the mature organism. If the pro—
cesses which are cited as important by psychoanalysis have
their basis in biological mechanisms, they should manifest
themselves in lower animals as well as in human beings
(Hunt, lQAl). Hebb and Thompson (1954), indicated that
work on animals is not directly applicable to man, but that
the principles underlying the effects of early experience
on later behavior are similar across all organisms. Since
it is impossible to employ on children the radical designs
which these experiments necessitate, the comparative study
is the next best method (Hebb and Thompson, 195A).

A good portion of the experimental work which has
been concerned with the question of the effects of early
reduced perceptual experience has been a direct outgrowth
of the work conducted by Hebb. Simply stated, Hebbian
theory proposes that animals having ”enriched” environments
early in life prove to be superior learners in adulthood.

He indicates that there is an inverse relationship between

the facilitative effect of an enriched environment, and

the age at which the perception is gained (Beach and Jaynes,
1954). Hebb posits that all learning uses and builds upon
the learning which has gone before. This early learning is
permanent and helps to make the behavior of the mature ani—
mal efficient (Hebb, 1949).

The aforementioned Hebbian principal of primacy of
effect is called into serious question by those theorists
who hold to the critical period hypothesis. Denenberg and
Karas (1960), found rats handled during the first ten days
of life to be superior learners, in adulthood, to those
animals handled during the second ten day period. Ss
handled on days 16—2O learned better than those handled on
days 11-15. These experimenters interpret their results in
terms of the critical period viewpoint, and indicate that
Hebbian theory does not adequately account for these
findings (Denenberg and Karas, 1960).

Different treatment at critical periods in the life of
an organism has produced differences in the adult agressive
behavior of mice (King, 1957), in the avoidance learning
of mice in adulthood (Denenberg and Bell, 1961), and in the
mortality rate of rats under conditions of terminal depriva—
tion (Levine and Otis, 1958). Griffiths (1961), found that
the same experience instituted at different periods of
development in the life of a rat, did not produce signifi—

cantly different performances on treadmill activity.

3

It is clear that there is disagreement as to whether
the earliest period of life is of greatest importance for
later behavior, or whether there are critical periods during
which an organism must make the necessary adjustments before
it can proceed to the following level. At present there is
both theoretical inconsistency and contradictory experi-
mental evidence within both points of view. It seems
however, that the major difference between the two positions
is more one of interpretation and emphasis than any other
single factor. There is general agreement that when you
provide manipulation of any sort to one group of animals
and not to another in early life, the latter are most
likely to manifest maladaptive behavior in adulthood.

There is a plethora of research evidence which indi—
cates the maladaptive nature of restriction in early life,
and the possible facilitative effects of gentling in in-
fancy on later reactions to environmental problems and
demands. The evidence for handling comes in part from the
work of Levine (1956), who has shown that rats handled
early in life tended to be superior in avoidance learning
to those animals who had received no such stimulation.

Clarke,_et_a1. (1951), found that dogs reared under
a restricted environment (i.e., one that employed reduced
visual inputs), were inferior in problem—solving ability
at maturity to those animals reared in a more complex

environment. Dogs deprived of early social and perceptual

experience were retarded with regard to the appearance of
normal adult social behavior (Melzack and Thompson, 1956).
At the same time, however, McMichael (1960), found that
differential treatment of rats in infancy did not yield
differences in response to various stress situations in
adulthood, nor in physiological damage under conditions
of deprivation.

Several investigators have interpreted the effects
of early treatment in terms of the emotionality of the
animal. Here again, the literature suggests that handling
seems to produce a more emotionally stable adult organism.
Where no handling is the treatment condition in infancy,
there may be a profound effect on the subsequent emotionality
of the animal (Levine, 1959). Lindzey, winston, and Manose-
vitz (1963), however, found that mice exposed to noxious
infantile stimulation were more highly emotional than those
used as controls. This evidence seems to contradict the
notion that all treatment, whatever its nature, serves to
produce a more adaptive organism than the one which has
received no such treatment in infancy. It similarly con—
tradicts those theorists who submit that infantile stimu—
lation stresses the organism, and is thus the cause for
the animal's reduced responsiveness to later stressing
events (Denenberg and Karas, 1960).

There is an important theoretical consideration

regarding methodology here, in that experimenters are equating

\J‘l

different experimental conditions. Generally, it is the
early handling experience that is considered by some to

be stressful. Thus, the experimental evidence seems to
indicate that the animal handled in infancy is more
capable of coping with stress in adulthood because it has
become ”accustomed” to stress in the past. Where intense
stimulation (shock, auditory) is used, or where reduced
sensory input is employed, the animal in both cases shows
maladaptive emotional adult behavior. In the former case,
the maladaptive pattern is produced by excess stimulation,
and in the latter by reduction of stimulation. Thus,
there are contradictory statements as to the effects pro—
duced by infantile ”stress” experiences of one form or
another. In view of this, it seems appropriate to consider
the procedures which are employed, and to question the
validity of generalizing a set of results obtained via one
experimental paradigm, to those which employ methodologies
differing in varying but marked degrees.

Although some kind(s) and amount(s) of early experience
sometimes exercise a profound effect on adult behavior, these
effects may be reversible, to some degree at least, by later
experiences in the life of the organism. Although the
effects of prolonged visual deprivation in infancy are
great in the adult animal, it appears that they do not need
to be permanent. Increasing practice with visually directed

responses tends to reverse the original effects (Beach and

6

Jaynes, 195A). woods (1959), for example, found that the
consequences of motoric and sensory deprivation in infancy
could be greatly reduced by subsequent exposure to an
enriched environment.

It is also the case that not all organisms react
similarly to varying environmental experiences. Various
species react quite differently to similar experimental
conditions. The effects of breed differences have been
reported by Lindzey, Winston, and Monosevitz (1963), and
by King and Eleftheriou (1959). Here again, however, it
seems advisable to proceed with caution; some evidence
indicates that the differences in behavior among species
that have been reported, do not necessarily reflect genetic
components, but rather, variations in the early environment—-
different species ”handle” their young in differing amounts

(Ressler, 1962).

CHAPTER II
PROBLEM

In view of the contradictory evidence presented with
regard to the possible facilitative or harmful effects of
early experience on adult behavior, the present study was
conducted in an attempt to clarify the nature of this
relationship. It was designed to partial out some of the
relevant factors which possibly serve to influence this
relationship—-factors which King (1958) and others (e.g.
McMichael, 1960), have suggested must be given further
experimental scrutiny.

Previous research suggests that animals reared under
conditions of reduced perceptual input show relatively
poorer later learning in problem—solving situations than
animals not so deprived (Beach and Jaynes, 1954; Melzack
and Thompson, 1956; Melzack and Scott, 1957). when and
how long such reduced perceptual input is experienced, also
seems to be associated with how such reduction will influ—
ence learning, if at all (Hebb, 1947; woods, 1959; Scott
and Marston, 1950; Denenberg, 1958, 1960). There is also
research precedent which suggests that attention needs to
be given to whether or not the form of a function found
between reduction of perceptual input and later learning

7

will vary with species (Rosen and Hart, 1963). Similarly,
it must be determined if the form of the relationship will
vary for genetic differences within Species (King and
Eleftheriou, 1959).

The present research investigates the following

dimensions: (1) Treatment-—involves varying periods of

 

time under conditions of reduced perceptual input; (2)

Litter-Mates-—consists of equal numbers of pups from

 

each mother assigned to all treatment conditions, permitting
scrutiny of genetic influences; (3) Species——two Species
are employed in an attempt to assess what influence species

differences have, if any; (A) Interactions——interactions

 

are checked to determine whether or not a treatment effect

holds for a certain Species only.

CHAPTER III
METHOD

The variations selected for investigation in manipula-
tion of Reduced Perceptual Input (RPI), and in Species and

Genetic differences are shown in Table 1.

Subjects

The sample of 6A deermice, obtained from the animal
colony of the Biology Research Center at Michigan State
University, includes 32 animals of each of the species
Peromyscus leucopus and Peromyscus polionotus.l Sixteen
females, casting litters of a minimum of four pups, met
the demands of balancing and the total N as indicated in
Table 1. When litters exceeded four pups the excess animals
were discarded according to a procedure which would maxi-
mize the number of males in the sample.

Animals were obtained in a staggered manner over a
two month period, with a restraint imposed to the effect

that no more than three successive litters from the same

Species appeared in the sample. This procedure eliminated,

 

1The following descriptive material is presented to
more thoroughly acquaint the reader with the physical and
behavioral characteristics of these two Species.

Peromyscus leucopus is found in forest and brushy areas
(Burt, 1957) throughout the east, midwest, and south. This

9

IO

.Haoo coflpfipcoo Ham x moflooow comm CH mpocbos Hmo
Iflmofioflp @H onb mo some Sosa non m ma opens .coflpflmossou poppflg x moflooom
o mood Dcwflo no annoy <m

x Coflpflpcoo Hum mo Coflpmoflwan oao hmzuoopcp onp pflw

 

 

 

asso ms-ws ages ms-am name ms-am name ms-am asaoeoaaoo .s

name maum: mans NSIQH mhmo mquwa swamp mSImH mSQOoSoH .m
opmg popcopxm xanmm Hohpcoo

:m u moss no .oc Hobos ncoflsflpcoo Ham mofloonm

QH H mnmcpoz mo .0: Hmuoe

 

 

mDBOZOHdom MDQMwZOmmL de WDSOODMQ mbomwzommm
IEZMEZUHmm< Eomflubm mo ZOHB<Bzmmmmmmm UHdemmom

H MQQ<B

11

in part, any massing of one species at the early or late part
of the experimental procedure. The transfer of all litters
and their mothers to the Psychology laboratory occurred when
the pups reached the age of 2—3 days.

All SS remained with their biological mother and three
litter-mates until weaning. At weaning each one of the four
pups in a litter was randomly assigned to one of the treat-
ment conditions. After weaning each S was caged separate
from any other animal and remained so for the duration of

the experiment.

Weaning, iarking, and Sex Determination

 

Weaning.——Weaning occurred at 18 days of age for
Peromyscus leucopus, and at 21 days of age for Peromyscus
polionotus.2 The four pups from any given mother were
randomly assigned to either the control condition or to

one of the three RPI conditions.

 

species' tail measures 2 2/5-4 inches, they weigh from
10.6—26.6 grams at adulthood, and achieve a length of 6—8 1/2
inches at maturity (Palmer, 1954). This largely herbivorous
spgcies bears an average of four young per litter (Golley,
19 2 .

Peromyscus polionotus is often referred to as the Old
Field or Beach mouse. This species is primarily found in a
dry sandy habitat (beaches), and in rock fields in the south—
eastern part of the U. S. (Palmer, 1954). They are a noc-
turnal animal and Spend the hot period of the day in the cool—
ness of their burrows. Peromyscus polionotus feeds primarily
on seeds of grass and herbs, and also on insects. They have
a short tail (1 3/5—2 2/5 inches), weigh from 8.3—1A.9 grams
at maturity, ranging from 5-6 1/2 inches. They bear an av-
erage of three young per litter (Golley, 1962).

2Pi1ot studies indicated that polionotus pups were less
capable of living at the age of 18 days, when separated from

l2

Marking.-—Since marking the SS when they were born
would have involved undesirable stimulation and handling
the necessity for this procedure was avoided by housing

all of the animals in individual living units.

Sex determination.——The sex of SS belonging to those

 

litters which had to be reduced to the required number

(viz., A), was determined when they had reached 2-3 days

of age. This procedure was followed in an attempt to ob-
tain a sample which consisted entirely of males, if possible.
Since each litter of four pups remained with its mother
until weaning, sex was again determined at that time for
each animal, before they were placed in the particular

treatment condition.3

 

their mother, than were pups from the leucopus strain. On
the basis of these results, and due to discussions with ex—
perts on the behavior of Peromyscus, it was decided that
different weaning ages would yield more maturationally com—
parable animals.

Precedence for this procedure appears elsewhere, as well.
King, Deshaies, and Webster (1963) employed a method in
which the weaning weight in the two strains of deermice was
determined by the age at which the weanling could maintain
itself without weight loss for a 24—hour period after sep-
aration from the mother.

3Agreement between early and late sex determination
was high; it was necessary to re-classify only three ani—
mals on the basis of later observations. This high rate
of agreement is primarily due to the technique employed-—
a puff of air was directed at the genital region of the
pup, which resulted in erection even in the immature male
animal.

13

Of the 64 SS, a total of 43 males (21 Peromyscus
leucopus and 22 Peromyscus polionotus), and 21 females (11
Peromyscus leucopus and 10 Peromyscus polionotus), were
represented in the final sample. The distribution of male
and female animals by treatment condition is presented

in Table 2.

TABLE 2

DISTRIBUTION OF MALE AND FEMALE SS
BY TREATMENT CONDITION

 

Species RPI Conditions

 

Control Early Extended Late

 

M F M F M F M F
P. leucopus 5 3 5 3 5 3 6 2
P. polionotus A A 7 1 5 3 6 2
TOTAL 9 7 12 4 10 6 12 4

 

Caging and Maintenance Activities

 

Caging.—-Prior to weaning, the four pups of each mother
remained together with the mother in one compartment of a
Thoren double cage constructed of clear plastic. The cages
were covered with a wire mesh top through which the animal
obtained food and water. These cages remained essentially
under the same conditions which will later be described as

the ”normal” laboratory environment setting.

14

At weaning all SS were individually housed in the
double cages. Each individual housing compartment measured
12 x 6 x 6 inches. Cages used in the RPI conditions were
covered with black plastic cloth on all sides (except the
top), eliminating the possibility of visual contact with
other animals. To further preclude any influence of
uncontrolled aspects of housing position, the animals were
randomly assigned to left or right position in the double
cage, and the cage, in turn, was randomly assigned to one
of two wooden bins.

The wooden bins measured 25 1/2 x 23 x A8 inches.
Each bin contained a shelf partition, and accommodated
four cages on the top shelf, and four on the bottom. Thus,
a bin housed a total of eight double cages, or 16 animals.
Black plastic cloth completely covered the bins, preventing
light leaks into the cages. Ventilation holes were also
baffled to prevent light leaks. A blower mounted on the
front of each bin ran continuously. The blower served the
triple function of ventilating the inner bin area, of pro—
viding a constant auditory stimulation pattern, and of
providing a relatively constant air flow pattern. Lining
each bin with Celotex material served to further attenuate

external auditory influx.

Maintenance activitieS.——After transfer to the

 

Psychology laboratory when the litter was 2-3 days old,

15

the mother and her litter were undisturbed until weaning.
Prior to weaning, the cages of all mothers and their litters
contained wood shavings and a wad of non-sterile absorbent
cotton. After separation from the mother, the weanling was
placed in its cage by use of a rubber—tipped forceps. These
cages contained fresh wood Shavings, a clean wad of non—
sterile absorbent cotton, and a fresh supply of water. A
handful of Old Fashioned Quaker Oats, strewn on the floor

of the cage, enabled the weanling to find food more readily
initially after separation from the mother, since the food
basket, located above the floor of the cage, could only be
reached by climbing.

The cages were not cleaned for the duration of the
experiment. None of the animals were handled after place—
ment in the appropriate RPI condition, except for the Early
and Late RPI groups. SS in these two latter groups were
handled with a rubber—tipped forceps at the age of A5 or
A8 days, at which time transfer to the opposite condition
occurred.

Food (Purina Laboratory Animal Blocks) and water were
availablezflilibitum until the time of testing. The tops
of the wire mesh cages held a supply of food which sustained
the SS throughout the experiment without need for replenish—
ment. The water bottles used contained approximately one
month's supply of water. Vater was replenished once for
all Ss while they were being reared, and once after testing

had begun.

l6

RPI Conditions

 

All SS were housed in the same room. This room con—
tained a powerful window exhaust fan which ventilated the
area. A constant room temperature of 80 degrees was
maintained. For purposes of this experiment, RPI was
defined as an unaltering pattern of visual and auditory
cues, and a relatively stable flow of air current. Vari—

ations in duration of RPI were as follows:

Extended RPI.-—All cages were placed in a totally

 

darkened wooden bin (see Caging, page 13). The animals
remained under the RPI conditions from weaning until the
start of testing at 72 days of age for the leucopus strain,

and at 75 days of age for P. polionotus.

Early RPI.--Animals in this treatment conditions were

 

reared under the RPI conditions until they reached A5 (P.
leucopus) or A8 (P. polionotus) days of age. At that time
transfer from the bin environment to the regular laboratory
environment took place, where the Ss then remained until

they were tested at 72 or 75 days of age.

Late RPI.-—From the time of weaning until A5 (P.
leucopus) or A8 (P. polionotus) days of age, the animals
remained under conditions of the regular laboratory environ~
ment. At this time they were transferred to wooden bin
environment where they then remained until testing at 72 or

75 days of age.

17

No RPI.——The control animals stayed in the normal
laboratory environment from weaning until testing at 72 or
75 days of age. The normal laboratory environment consisted
of a 2A—hour light cycle, and visual stimulation from exter—
nal sources. The animals were visually exposed to each
other, and to a variety of other animals maintained in the
same room @Lg., rats and quail). Thus, a varying pattern

of auditory and visual cues prevailed for this group.

Testing Apparatus, Procedures, and Measures

 

The test cage, constructed of the same plastic material
as the home cage, contained a metal mesh floor and sides
whichvmnmewired in a series circuit with the metal spout of
a water bottle and an Applegate Stimulator. The animal
completed the circuit upon coming irfio contact with the
electrified water spout, permitting the delivery of shock.

At 72 or 75 days of age, each S was placed on a A8—hour
deprivation schedule. Immediately after a A8—hour depriva-
tion period, the animals were weighed (i.e., prior to each
test trial), after which they were placed in the test
apparatus.

The animal to be tested was removed (in the test cage)
to a cubicle in another room, where testing took place.

This cubicle served the function of reducing auditory and
visual stimuli presented by the other laboratory animals,

and by experimental research being conducted by others.

18

The following procedures obtained on each test trial:

1. Habituation to the test apparatus (i.e., test
cage and cubicle), for a period of eight minutes occurred
before testing was begun. Following this habituation
period, water was presented via an inverted metal drinking
tube. The amount of time necessary for any particular S
to discover that water was present (i.e., on the first
test trial), was recorded.

2. When the animal began to lick the water tube,
shock was introduced. Increasing levels of shock were
presented, and the shock level required to drive the
animal away from the water was recorded.

3. When the S returned to drink for a second time,
a record was obtained of the amount of shock necessary to
drive the animal away from the water once more.

These three pieces of behavior (i.e., time taken
to drink, level of initial shock taken, and amount of
shock taken on return), defined one test trial. If this
behavior pattern did not manifest itself within a five-
minute period, the trial was defined by the five—minute
time interval rather than by the behavior, If the animal
did not perform the required behavior within the five—
minute period, he was removed from the testing situation
and returned to his home cage for a period of 72 hours.
The 72-hour interval between test trials similarly

applied to those SS who had manifested the three pieces of

l9

behavior which satisfied the alternate definition of
a test trial.

During the first 2A—hours of this 72—hour period in
the home cage, water was available. Immediately after
this 2A—hour period the A8—hour water deprivation schedule
was reinstituted at the end of which the animal's weight
was noted, and the testing procedure repeated.

The number of trials during which an S took shock in
order to receive water was noted. An animal was considered
to have manifested "conditioned avoidance behavior” on that
trial during which he avoided contact with the water tube
for the entire five-minute test period.

Once an animal had exhibited avoidance behavior an
extinction procedure obtained. The measure here consisted
of the number of trials that it took for the animal to
resume drinking (i.e., extinction of conditioned avoidance
behavior) in the same situation which had previously coupled
aversive stimulation with the ”desired” object——water, and
which the animal had learned to avoid. Prior to each extinc—
tion trial, the SS were maintained on the same 72-hour
schedule——i.e., 2A—hours on water, A8—hours water—deprived.
Testing terminated at that point where the animal found
that shock no longer accompanied licking the Spout, and
began to drink within the confines of a five—minute test
period. The number of trials that it took an S before he

resumed drinking was recorded.

20

The experimental literature clearly indicates that
sensorily deprived animals learn more slowly and adapt
more poorly to novel situations than do animals not so
deprived. In addition, there is contradictory evidence
which suggests, on the one hand, that the deprived animal
will be less reactive to noxious stimulation in adulthood,
and on the other hand, that such early deprivation will
yield a "stressed" organism——one which will be more reactive
to aversive stimulation. The different reSponse measures
were selected in order to permit analysis more specifically
bearing on these points. The following measures were sub-
jected to statistical analysis:

1. The amount of time (in seconds) that it took

for an experimentally naive animal (i.e., one

that had never had water presented previously

in the test apparatus), to discover the pres-

ence of water--i.e., Initial Time to Discovery
(ITD) .

2. The amount of shock (in milliamps) necessary
to drive the experimentally naive S (i.e., one
which had never previously had shock presented
in contiguous association with water), away
from the water Spout——i.e., Shock Taken—the
First Time Given (SFT).

3. The number of trials which it took to manifest
conditioned avoidance behavior—-i.e., Trials
to Conditioning (TC).

A. The number of trials which it took for the
animal to resume drinking in the test appara-
tus once conditioned avoidance behavior had
manifested itself—~Trials to Extinction (TE).

The ITD measure bears on the question of the adapta-

bility of the animal in a novel situation. SFT bears on

21

the question of greater or lesser reactivity to aversive
stimulation on the part of the mature S who had been
reared under reduced input conditions. The TC and TE
measures have to do with the question of retarded learning
ability for the RPI animals.

The literature also indicates that body weight gain
from infancy to adulthood is somehow also influenced by
RPI rearing conditions. Two body weight measures were
therefore.inc1uded:

l. The SS Weight (in grams) at Weaning (WW).

2. The Ss weight gain (in grams) from the time of
weaning until the first trial, divided by the
animal's weight at weaning--i.e., the Proportion
of Net Weight Gain from Weaning to Maturity (NWG).

WW was determined in order to assess the possibility
that one particular treatment group had a weight advantage
on the basis of random assignments alone. The NWG measure

relates to the question of the deleterious or facilitative

effects of the RPI conditions on body weight.

CHAPTER IV

RESULTS

The F and associated p values for treatment, litter—
mate, species, and treatment by species interaction effects
are presented in Table 3 for each measure. Full summaries
of the analysis of variance on each of the four reSponse and

1;

two body weight measures are presented in Appendix A.

Treatment Effects

 

As shown by the data in Table A, the significant treat—
ment effect on the SFT measure is basically attributable to
the interaction of treatment and species. The interaction
is illustrated in Figure 1. Significant simple effects occur
only with the extended RPI animals of the Species P. polio—
notus; they take significantly less shock than either their
P. leucopus counterparts or the control P. polionotus animals.

Although an analysis of variance indicated no main or
interaction effect of treatment on the ITD or TC measures,
in view of the skewness and variability of these response

measures further analyses were carried out using nonparametric

 

”A total of five animals (all P. leucopus) perished
during the rearing and testing period. A score was calculated
for their empty cell by using the row and column means for
their species. A reduction of one degree of freedom was made
for each such calculation.

22

23

 

 

 

 

 

 

 

.n.s Hv Ho.v oa.m Hoo.v sm.on n.c Hv A.nem cav 5:2
.c.s HH.m Ho.v mo.n .n.s ms.a h.s mo.m A.nsw sav 33
monsmmoz pnwfloz abom
.n.s sm.H mo.v ma.m .n.c cm.m n.c av as
.n.: so.m Ho.v mm.m Ho.v mw.am n.s Hv on
mo.v os.m mo.v mm.m .n.s A. ,m.v om.s A.oe saw saw
.n.e Av .o.e mm.H mo.v om m a.c mm.fi A.oon cav can
Q m o m Q m o m
moflommm x E opmzlpoppflq nowoonm pnoepmmgs

 

®UCQHHQ> .HO wOvHSOW

monSmmmz omnoomom

 

 

mmmbm<mz BEUHME

wflom QZ< mmzommmm mom

m mamas

mmpq<> a oza a

2A

TABLE A

MEAN SFT SCORES (IN MILLIAMPS) FOR Ss GROUPED
av SPECIES AND_TREATMENT

 

 

 

 

Species RPI Condition

Control Early Extended _ (Late
P. leucopus .0638 .0500 .0613a .0625
P. polionotus .0900b .0500 .02638’b .OA38
Combined .0769C .0500 .0438 .0531,

 

a’bVertically adjacent entries with superscript g and
horizontally adjacent entries with superscript S are sig-
nificantly different from one another at the '.05 level or
less; by Mann-Whitney U tests.

CThe combined control group differs (p .05) from each
Of the combined RPI groups; none of the combined RPI groups
differs from one another.

tests. The data were grouped by treatment and species and
analyzed by a Kruskal-Wallis H test. The H values are sig—
16.73,
7,

nificant for both ITD and TC: for the ITD analysis H

df = 7, p <.O2; and for the TC analysis H = 27.01, df

p .001. The results of further analysis for simple group
differences by the Mann—Whitney U test on ITD and TC are
presented in Tables 5 and 6, respectively. On the ITD there
are no differences among the treatment groups of P. leucopus,
while within the species P. polionotus the early and late

RPI groups both discover water significantly faster than the

pcoEpmone
Opmq nonempxm mfinmm Hoppcoo

r n,( F A
_ C d _

.IIII.II.l.m5po:oHHOQ mzomhsonom //

 

mzoooBOH moomhsonom ./

mZOHEHQZOU BZMEB<mmB QZ<
mmHommm mom ZMK<B MOOSW EmmHm mo mmbd<> Z<m2

H mmDUHm

1H0.

imo.

rmo.

 

(OH.

sdwetrttw u: xooqs jo iunomv aBeaaAv

26

TABLE 5

MEAN ITD SCORES (IN SECONDS) FOR SS GROUPED
BY SPECIES AND TREATMENT

 

 

 

 

Species RPI Condition

Control Early Extended Late
P. leucopus 798 6258 1293 281
P. polionotus 151 15Aa’13 513b’C 289C

 

aVertically adjacent entries with this superscript are
significantly different at the .05 level or less.

b’CHorizontally adjacent entries witn the
script are significantly different from one a
.05 level or less.

some super—
ags‘ ,‘ Law.
Lather at tut

TABLE 6

MEAN TC SCORES FOR SS GROUPED BY SPECIES
AND TREATMENT

 

 

 

 

Species RPI Condition
Control Early Extended Late
P. leucopus 4.63 3.25a 3.38a 3.753
,b a “,5
P. polionotus 6.75b 11.008 9.50 7.251

 

a’bVertically adjacent entries with superscript g and
horizontally adjacent entries with superscript S are signif—
icantly different from one another at the .05 level or less.

extended RPI group. The P. caliototus early RPI group at
discovers water significantly faster than its P. leucopus
counterpart. 0n TC the control and three RPI groups of

P. leucopus show an equally rapid rate of conditioning. In

the cas of P. polionotus, the control roup conditions more

(‘9

rapidly than the early RPI group, and all three RPI group:

take longer to cordition than their respective P. leucopus
5
counterparts.“

 

on the lib, TC, and WW3 measures are in.icated by the data
presented in Table 7. P. leuc,r1s takes significantly
longer to discover water, leurr: more rapidly to avoid The

electrified water tube, ard tends To take longer to ex—

tinguisn. As expected, P. leucopus gains proportionately

\J

more weight from weaning to maturiTv——it being the larger

of the two species at maturity. diin respect 1; ITD and T‘.

however, it is in ortant to recall trat the Species effect

does not hold regardless of treatment condition. And, as
noted in presenting the treatment results, on SFT there is

also an interaction between treatment and srecies.

 

[2
’The results are the same whether trials to condi-

tioning or number of shocks to conditioning are used.

 

)M‘
i

TABLE 7

"T VALUES FOR

WHEN RESPONSE AND BODY WEISH
POLIQNOTUS

P. IEUCOPUS ANC’P.

 

 

 

 

Response Measure Species l

P. leucopus P. polionotus
lTD {in sec.) 74) 277 <.05
SFT (in ma.) .039W .053? --—-
to 3.8 8.6 <.C'l
TB 9.4 1.5 .10— C“

 

 

Body Meigtfi ikaisures

 

l—J .
L1
UQ
3
C")
“\J
OD
r—4
N
W
l:

/‘.

a \J

(H)
}__Jo
'\
Wt!
.7
p_l
o
\ )7
\U
.
Y]
H
A

 

29

Litter-Mate Effects

 

There is an effect associated with this factor on all
the measures except ITD. The large variability among litters
within and across Species is evident from inspection of the
same mother litter—mate means presented in Table 8. It
i;years that this source of variance has a more generalized
effect on the measures under consideration in this research

firth does either treatment or species per se.

Sex Differences

 

A check for possible sex differences was made on all
measures. Comparisons within and across both Species reveal

differences. Mean values for male and female §s on eacm

lues

{D

of the measures are presented in Appendix F. Mean v
for male and female §s of both species are presented in

Appendix G.

30

TABLE 8

MEANS OF THE FOUR PUPS FROM THE SAME
BIOLOGICAL MOTHER ON EACH MEASURE

 

 

Mother # Response Measure Body Weight Measure

 

ITD SFT T C TE NW N W G

 

P. leucopus

 

 

 

1 499 0575 6 00 1 50 8.25 1.22
2 183 0500 4 00 2 5 8.23 1.47
3 1123 0625 2 75 2 00 7.63 1.74
4 162 0450 2 00 4 50 6.38 2 12
5 1221 0550 2 25 4 - 7.95 1 5
6 1438 0600 3 00 1 50 8.70 1.63
7 1056 0475 6 c0 2.0c 6.90 1.44
8 314 .0975 4.00 1.25 8.45 1.37
P polionotus
1 702 .0400 11.25 1.50 6.83 65
2 597 .0450 8.75 1.00 6.85 1 c9
3 123 .1100 13.00 3.50 6.90 ”5
4 156 .0225 8.00 1.00 7.95 4:
5 185 .0300 6.25 1.75 8.33 14
6 104 .0600 7.50 1.00 8.15 .31
7 143 .0725 6.28 1.00 7.08 52
8 203 .0400 8.00 1.25 6.63 42

 

CHAPIER V

DISCUSSION

1

n this

Ho

:ed

l

(

fhe response and body weight measures u;
research were selected in order to possibly clarify some
of the contradictory experim ntal eviderre found in the
literature, and tecause the results obtained by use of
these measures presumably fit under the major interpretive
formilations commonly applied to data cn experiments in
which tne opportunity for perceptual experience is severely

restricted. The reSponse measures used were tho

(I)

e COH-
sidered to be most likely to reflec: differences which might
obtain due to the nature of the particular treatment con—

dition under which an animal nad been reared. Thus,

Q)

“can ‘ "3"“ : Up
5.3 k.) 1-" L. 1 '_. L \‘ C.

conditioning and extinction behavior, which are

or learned phenomena- phenomena which the experimental
literature suggests are markedly disturbed by conditions
of reduced sensory imput—-were included. In addition,

recording initial time to the discovery of water makes i;

possible to determine which, if ary, of the treatment

0.)

conditions produces a more adaptable animal—-ad.p ability

(

here construed as a greater length of time necessary to

discover water. Similarly, the experimentally naive

animal's ability to withstand increasing levels of shock

w.s studied in light of the evidence which exists that the

H)

deprived animal is either more reactive to painful stimula—
tion or that he is less reactive to such stimulation.
Finally, the net body weight gain from weaning to maturity
was observed since there are also reports as to the detri—
mental or facilitative effect of restricted sensory environ—
ment upon this measure.

What can be said regarding the lindings? First off,
the results as a whole are not adequately accounted for by
either of the two so-called general and rather opposed sets
of notions which have been proposed to describe the effects
of reduced sensory input. One formulation is that somehow
(mechanism unknown), reduced perceptual experience early in
life results in a decrement in appropriate reSponsiveness
to painful stimulation later in life, and, in addition,
this decrement becomes more pronounced in direct relation
to the period of time during which the reduced perceptual
input is in force. Within the conditions of the present
experiment, this suggests that the Extended RPI condition
should have been more deleterious on avoidance learning
than either the Early or Late RPI conditions. Further,
the Early RPI condition should have been more detrimental
than the Late RPI condition (woods, 1959). And compared
to control animals, all three RPI conditions should hav
been associated with significant decrements in learning to

avoid painful stimulation.

33

The results of the present experiment do not support
this position in any sufficiently general or systematic way.
No particular RPI condition per se was more detrimental to
an animal's reactivity to shock, quickness to discover
water, and ability to learn to avoid painful stimulation.
If anything, the results obtained on the first shock
measure, for example, would contradict the notion that RPI
conditions necessarily produce more maladaptive behavior
patterns in the mature organism. The first formulation
would also predict that the RPI groups would take the great—
est amount of shock before retreating from the aversive
stimulus. Actually, the results indicate that the EFT
groups tended to take the least amount of shock before
withdrawal, whereas the control group took the greatest
amount of shock.

In contrast to the first formulation, the second
maintains that the animal reared under conditions of
reduced stimulation should be more ”emotional” or reactive
so that if faced with an avoidance learning situation he
should learn more quickly, if not more efficiently. This
suggests rather opposite predictions from the first inter—
pretation (Levine, 1959). For example, it would be pre—
dicted that the Extended RPI condition should yield animals
which learned to avoid most quickly, whereas the ”normal”
environment animals should take longest. The Extended RPI

group, however, does not react more readily to shock. For

34

that matter, there are no overall treatment effects. Rather,
there are simple treatment—species effects that suggest that
a particular treatment may increase, decrease, or have no
influence on the animal's response characteristics.

Both formulations are inadequate on still other grounds.
Neither one actually incorporates or really allows for such
things as litter or species influences. In reviewing the
literature, one becomes impressed also with the lack of
information provided regarding the biological line of descent
of the §s used. Frequently it is found that even if the
type or strain of animal is reported, little information is
provided beyond this. On the basis of this lack of mother
or litter information, it is presumed that few, if any,
precautions are taken in this regard. Yet, if litters from
only two mothers were used in two different treatment condi—
tions, and should there be some large genotypic difference,
the results would most certainly differ. And, although
these differences represent little more than artifact,
they nevertheless would be attributed to differences pro-
duced by variations in treatment condition, or at best
placed in an error term. On the other hand, if a larger
number of litters is used and this genotypic influence
is sufficiently strong, it could obliterate any small
treatment effects which might otherwise be found. Were
this the case it would account for the lack of support of

those studies which find treatment differences but use

litters from only a few mothers. Just as conceivable, of
course, is the situation where litter and treatment differ—
ences fortuitously combine to make "treatment effects" ap-
pear even larger. Whether or not such interpretations

might account for why some experiments find that different
treatments early in life produce differences in, for example,
avoidance learning in adulthood (Denenberg and Bell, 1961;
Levine, 1956) while others do not (Tapp and Markowitz, 1963),
remains a question to be answered by future research.

The fact that Species differences had a marked influ—
ence on the results bears out earlier findings. Several
experimenters have recently cited the importance of such
differences, for example, on avoidance learning in mice
(Collins, 1963, 1964; Roberts, 1962). In the present ex—
periment, P. leucopus took a longer time to "discover"
the presence of water, which can be taken as one indication
of the greater adaptability of this species. That is, such
”cautious” behavior is very necessary in dealing with the
unfamiliar in the natural habitat. Similarly, the finding
that P. leucopus both conditioned more rapidly and tended
to extinguish more slowly can also be construed as suggesting
the greater adaptability of this species. In this instance
there would seem to be at least a two—fold problem in the
conditioning situation used. The §s had to de—condition

(or extinguish)reSponsessuch as extraneous grooming behavior

36

before conditioned avoidance could occur to the aversive
stimulus.6 And P. leucopus was more rapid in the presumed
de—conditioning of these interfering responses. This way
of viewing the differences between the two species is in
agreement with previously described differences between P.
leucopus (Southwick, 1964) and P. polionotus (Horner, 1954).
Being in agreement does not mean, however, that the fore-
going presentation is sufficiently accurate. The results
clearly show that whether or not differences between the
two Species are found, as well as the direction of the dif—
ferences, depends in a given instance on either the treat—
ment condition or the behavior being looked at or both.

The real possibility also exists that the avoidance
conditioning results of simple treatment—Species effects
are further restricted in their generalizability in the
sense of being peculiar to the test procedure used.
Actually, the test procedure used is more fashionably re—
ferred to as ”punishment training” rather than avoidance
conditioning. Kimble (1961) describes the subtle but
seemingly important difference: the punishment procedure

entails the occurrence of aversive stimulation contingent

 

Contrary to the findings of many other experiments,
very little freezing behavior contiguous with the shock
stimulus was observed. This may be best explained by the
fact that an animal could take shock up to his particular
threshold and then retreat. In most other studies the
shock is not yoked in this way, but is a constant above
threshold quantity.

37

upon the manifestation of a specified response, whereas in
avoidance training, the painful stimulation obtains only
in those situations in which the response fails to occur.
Punishment training, then, refers more directly to the
process by which both positive reinforcement and noxious
stimulation are contingent upon a response. As such, in
this procedure, the response (drinking) mediates between
the discriminative stimulus (water tube), and the punishment
(shock)(Church, 1963). Kimble (1961) further points to
experimental evidence suggesting that shock in the presence
of water leads to the conditioning of responses to the
cues in the shock situation which are incompatible with
drinking. Further, the amount of response suppression
seems to be greater with punishment training than it is
with avoidance training. In punishment training water may
serve the function of a conditioned stimulus for shock
onset and thus becomes a noxious stimulus (Solomon, 196M).
In the context of the present experiment, then,
conditioning probably occurs as follows—-the unconditioned
fear response to shock became associated with the discrimi—
native stimulus (i.e., the water tube) through classical
conditioning. Since noxious stimulation is administered
in conjunction with contact with the water tube, the rate
of responding for the positive water reinforcement is
suppressed (ala Church, 1963). Also, since a punishment

training method was used, once conditioning takes place a

38
rather lengthy period should follow before extinction
occurs. This was not, however, the case--extinction oc-
curred within one or two trials after the animal was placed
in the test situation and his licking response to the water
tube was not negatively reinforced. This apparently contra-
dictory result, however, appears not to be so contradictory.
It seems to be a rather common finding that although punish—
ment training produces greater suppression of consummatory
responses than avoidance training (Solomon, 1964), there is
a concomitant decrease in the resistance to extinction with
this procedure (Church, 1963). One possible explanation
for such rapid extinction has recently been proposed by
Denny and Weisman (1964). They found that a long period
of time (e.g., 225 seconds) in a test compartment, without
the presence of shock for a good part of that time, actually
serves to facilitate subsequent approach behavior during
avoidance learning. They suggest that this large ratio
of nonshock to shock time permits the animal to first learn
to relax in the test compartment, and that this relaxation
pattern is readily reinstituted yielding more rapid extinc—
tion. Whatever the case may be regarding how well this
explanation fits the test situation of the present experi—
ment, it has not to date been stated in such a form as to
also account for the species—treatment effects in conditioning
found in this experiment. Such a refinement in formulation

appears to await further work.

39

It does seem certain that many factors are likely to
be operative in an interdependent or combining way in most
experiments studying the effects of early experience on
later behavior (e.g., see Baumeister, Hawkins, and Cromwell,
1964; King, 1958; McMichael, 1960). To pretend that such
is not the case, or to ignore at least the serious possi-
bility that it is the case, would appear to have had both
advantages and disadvantages. Two major advantages appear
to be that wider generalization of results is possible, and
in turn, interpretations can remain essentially unchanged.
The disadvantages seem to be that there is an increasing
lack of fit between empirical evidence and theory, over—
inclusive statements are made regarding the generalizability
of findings, psychological or physiological concepts are
created to account for results that are due only to methodo—
logical artifacts, and much empirical research that should
get done does not get done. In the long run the disadvan—

tages ought to outweigh the advantages.

CHAPTER VI
SUMMARY

The present study investigates the influence of
perceptual experience, litter background and species dif-
ferences on avoidance behavior and body weight.

Manipulation of perceptual experience consisted of
placing an animal in a highly reduced perceptual input (RPI)
environment (i.e., darkness, masked sound, and visual iso—
lation from other animals). It was introduced at one of
three times of age: viz., just after weaning for 27 days
(Early RPI), the 27 days just before testing began (Late RPI),
and just after weaning for 54 days (Extended RPI). A control
group remained in the open laboratory environment for 54
days after weaning.

Eight P. leucopus and eight P. polionotus mothers
casting a minimum of four pups each supplied the total
sample of 64 SS. Each pup from the same biological mother
was randomly assigned to one of the three experimental
conditions or to the control group. Each group consisted
of a total of 16 animals, eight from each of the two
species.

In testing for effects on later avoidance behavior,
measures were taken of the time required for discovery of

40

41

water in a novel setting, reactivity to Shock, and rapidity
of avoidance conditioning and extinction. A punishment pro—
cedure was employed by means of which an aversive shock
stimulus was coupled with a consummatory drinking response.
Testing was begun for an S when it had reached maturity,

and continued until he had successfully learned to avoid

the aversive stimulation, and then had subsequently come

to extinguish this avoidant behavior in the absence of
Shock. Body weight was determined throughout testing.

The results clearly indicate that whether or not RPI
has an effect on avoidance behavior, as well as what the
direction of the effect will be, depends upon both the
species of the animal and the particular behavior being
looked at. Since there is no general systematic effect
associated with the RPI treatment dimension, it was con—
cluded that diminished sensory input per se during the
early life of an organism does not permanently effect
performance in terms of reacting to noxious or novel stimu-
lation, learning to avoid an aversive stimulus, or extin-
guishing avoidance behavior.

Both litter background and Species differences occur
on almost all measures. The importance of these factors
is emphasized Since frequently the experimental literature
fails to report adequate controls for these variables. It
is proposed that many previous results which find in favor

of, or against, the ”effects of early experience” may be

spuriously derived due to the use of litters from just a
few mothers, or a strain of one type.

In general the findings do not lend support to the
so—called Hebbian position that an animal reared under a
reduced sensory environment will be more retarded at
maturity in the ability to learn, and to respond to
aversive stimulation, than will animals not so deprived.
Neither do the results support another major theoretical
formulation which posits that the early environmental
Situation, where stressful, will yield a mature organism that
is better adapted to cope with his environment, or one that
is more reactive to a later stressful Situation.

On the basis of present and previous results, it
seems clear that there are many factors which are inter—
dependent and serve to influence the effects of early RPI
on later behavior. Such factors as the measuring device,
the environment (housing) of the §S, sex, age, and Species
need to be considered in the interpretation and generaliza-

tion of any particular set of results.

BIBLIOGRAPHY

43

BIBLIOGRAPHY

Baumeister, A., Hawkins, W. F., and Cromwell, R. L. Need
state and activity level. Psychol Bull., 1964, 61,
438—453.

 

Beach, F. A., and Jaynes, J. Effects of early experience
upon the behavior of animals. Psychol. Bull., 1954,
51, 239—263.

 

Bingham, W. E., and Griffiths, W. J. The effect of differ—
ent environment during infancy on adult behavior in
the rat. J. comp.4physiol. Psychol., 1952, 45, 307-
312.

 

Burt, W. H. Mammals of the Great Lakes Region. Ann Arbor:
University of Michigan Press, 1957.

 

Church, B. M. The varied effects of punishment on behavior.
Psychol. Rev., 1963, 70, 369—402.

 

Clarke, R. S., Heron, W., Fetherstonhaugh, M. L” Forgays,
D. G., and Hebb, D. 0. Individual differences in dogs;
Preliminary report on the effects of early experience.
Canad. J. Psychol., 1951, 5, 150—156.

 

Collins, R. L. Inheritance of avoidance conditioning in mice:
A diallel study. Sci., 1964, 143, 1188—1190.

Denenberg, V. H. Effects of age and early experience upon
conditioning in the C57BL/lO mouse. J. Psychol.,
1958, 46, 211—226.

 

Denenberg, V. H. A test of the critical period hypothesis
and a further study of the relationship between age
and conditioning in the C57BL/lO mouse. J. genet.

Psycho., I960, 97, 379—384.

Denenberg, V. H., and Bell, R. W. Critical periods for the
effect of infantile experience on adult learning.
Sci., 1961, 131, 227—228.

Denenberg, V. H. and Karas, G. G. "Interactive effects of
age and duration of infantile experience on adult learning
Psychol. Rep , 1960, 7, 313—322.

Denny, M. R., and Weisman, B. G. Avoidance behavior as a
function of length of nonshock confinement. J. comp.
physiol. Psychol., 1964, 58, 252-257.

44

 

 

Golley, F. B. Mammals of Georgia. Athens: University of
Georgia Press, 1962.

 

Griffiths, W. J. Effects of isolation on treadmill running
in the albino rat. Psychol Rep., 1961, 8, 243-250.

 

Hebb, D. O. The effects of early experience on problem—
solving at maturity. Amer. Psychol., 1947, 2, 306-
307.

 

Hebb, D. O. The organization of behavior. New York:
John Wiley, 1949.

 

Hebb, D. 0., and Thompson, W. R. The social significance
of animal studies. In G. Lindzey (Ed.), Handbook of
social psychology. Cambridge: Addison Wesley, 1954.

 

 

Horner, B. Elizabeth. Arboreal adaptations of Peromyscus
with special reference to the use of the tail.
Contr. Lab. vert. Biol., 1954, No. 61.

 

Hunt, J. McV. The effects of infant feeding frustration
upon adult hoarding in the albino rat. J. abnorm.
soc. Psychol., 1941, 36, 338-360.

 

 

Kimble, G. A. Hilgard and Marquis' conditioning and
learning. New York: Appleton-Century—Crofts, 1961.

 

King, J. A. Belationsnip between early experience and
adult aggressive behavior in inbred mice. J. genet.

Psychol., 1957, 9o, 151—166.

King, J. A. Parameters relevant to determining the effects
of early experience upon the adult behavior of animals.
Psychol. Bull., 1958, 55, 46—48.

 

King, J. A., Deshaies, J. C., and Webster, R. Age of weaning
in two subSpecies of deermice. Sci., 1963, 139, 483—

484.

King, J. A., and Eleftheriou, B. E. Effects of early handling
upon adult behavior in two subspecies of deermice,
Peromyscus maniculatus. J. comp. physiol. Psychol.,
1959, 52, 82-88.

 

Levine, S. A further study of infantile handling and adult
avoidance learning. ‘J. Pers., 1956, 25, 70—80.

Levine, S. The effects of differential stimulation on emo—
tionality at weaning. Canad. J. Psychol., 1959, 13,
243—247.

 

46

Levine, S. and Otis, L. S. The effects of handling before
and after weaning on resistance of albino rats to
later deprivation. Canad. J. Psychol., 1958, 12,
103—108.

 

Lindzey, G., Winston, H. D., and Manosevitz, M. Early
experience, genotype, and temperament in Mus Musculus.
J. comp. physiol. Psychol., 1963, 56, 622—629.

 

McMichael, R. E. The effects of preweaning shock and
gentling on later resistance to stress. Doctoral
dissertation, University of Illinois, 1960.

Melzack, R., and Scott, T. H. The effects of early experi—
ence on the response to pain. J. comp. physiol.

Psychol., 1957, 50, 155—161.

 

Melzack, R., and Thompson, W. R. Effects of early experi—
ence on social behavior. Canad J. Psychol., 1956,
lo, 82—90.

 

Palmer, R. S. The mammal guide. Garden City: Doubleday,
1954.

 

Roberts, L. E. Genotype as a determinant of electrical
and behavioral reactions to Shock stimulation in the
mouse. Unpublished research report, University of
Minnesota, 1962.

Roberts, L. E. Genetically influenced mechanisms mediating
behavioral reactions to aversive stimulation. Unpub—
lished research report, University of Minnesota, 1963.

Rosen, J., and Hart, F. M. Effects of early social isolation
upon adult timidity and dominance in Peromyscus.
Psychol. Rep., 1963, 13, 47-50.

 

Scott, J. P., and Marston, M. V. Critical periods effecting
the development of normal and mal-adjustive social
behavior of puppies. J. genet. Psychol., 1950, 77,

 

 

25—60.

Solomon, R. L. Punishment. Amer. Psychol., 1964, 19,
239-253.

Southwick, C. H. Peromyscus leucopus: An interesting subject
for studies of socially induced stress reSponses. Sci.,

 

1964, 143, 55—56.

47

Storms, L. H., Boroczi, C., and Broen, W. E. Effects of
punishment aS a function of strain of rat and dura-
tion of shock. J. comp. physiol. Psychcl., 1963,
56, 1022—1026.

 

Tapp, J. M., and Markowitz, H. Infant handling: Effects
on avoidance learning, brain weight and cholinesterase
activity. Sci., 1963, 140, 486—487.

Tetzlaff, T. J. The effects of early handling on the adrenal—
cortical response to stress as measured by circulating
corticosterone. Doctoral Dissertation, Michigan
State University, 1964.

Woods, P. J. The effects of free and restricted environ—
mental experience on problem—solving behavior in the
rat. J. comp. physiol. Psychol., 1959, 52, 399—402.

 

APPENDICES

48

A P PIE DI X A

 

 

 

 

 

 

 

ANALYSES OF VARIANCE
Source SS DF MS F
Initial Time to Discovery (in seconds)

Treatment 16,221 3 5,407 n.s.
Treatment x Species 8,381 3 2,794 n.s.
Treatment x Mothers

within Species 169,045 38 4,449
Mothers 80,497 14 5,750 n.s.
Treatment x Mothers 177,426 41 4,327
Species 31,507 1 31,507 8.36, p<.05
Mothers within

Species 48,990 13 3,768

Shock Taken—the First Time (in milliamps)

Treatment .010082 3 .003361 4.20, p«.CT
Treatment x Species .008305 3 .002768 3.46, p<.CE
Treatment x Mothers

within Species .030363 38 .000799
Mothers .030594 14 .002185 2.32, p’.05
Treatment x Mothers .038668 41 .000943
Species .000757 1 .000757 n.s.
Mothers within ‘5

Species .029837 13 .002295

Trials to Conditioning

Treatment 26.63 3 8.88 n.s.
Treatment x Species 77. 2 3 5.71 n.s.
Treatment x Mothers

within Species 471.75 38 12.42
Mothers 606.25 14 43.30 3.23, p.<01
Treatment x Mothers 548.87 41 13.39
Species 380.25 1 80.25 21.88, p atl
Mothers within

Species 226.00 13 17.38

 

51

ANALYSES OE VARIANCE

 

 

 

 

 

 

 

 

Source SS DF MS F
Trials to Extinction

Treatment 4.06 3 1.35 n.s.
Treatment x Species 8.81 3 2.94 n.s.
Treatment x Mothers

within Species 83.13 38 2.19
Mothers 75.94 14 5.42 2 42, p« 05
Treatment x Mothers 91.94 41 2.24
Species 14.07 1 14.07 n.S
Mothers within

Species 61.87 13 4.76

Proportion of Net Weight Gain from Weaning
to Maturity (in grams)

Treatment .47 3 .16 n.s.
Treatment x Species .51 3 .17 n.s.
Treatment x Mothers

within Species 7.64 38 .20
Mothers 23.39 14 1.67 8.40, p<.01
Treatment x Mothers 8.15 41 .20
Species 19.01 1 19.01 56.37, p< .001
Mothers within

Species 4.38 13 .34

Weight at Weaning (in grams)

Treatment 2.72 3 91 n.s.
Treatment x Species 2.86 3 5 n.s.
Treatment x Mothers

within Species 17.23 38 .45
Mothers 34.71 14 2.48 5.06, p<.01
Treatment x Mothers 20.09 41 .49
Species 3.56 1 3.56 n.s.
Mothers within

Species 31.15 13 2.40

 

APPENDIX B

52

DJ
F/

 

 

 

 

 

 

 

 

 

 

 

 

an. az.m oo. mm.c m. ms.z rm. no.1 owsao><
:m.z mm.m am. mm.a ea. 66.2 »m. mm.a .o .a
om. ma.m ma.mw ma.m aa.a. om.m 1s. loo.m .H .a
mm
os.m ow.m as.a as.o mm.a ma.s om.m mo.m omotosa
a8.m mm.» mm.oa 6m.o so.os oo.aa ms.w ma.@ .6 .a
sm.m ms.m mnim, mm.m so.a mm.m mans mc.s .a .a
De
mmooo. ammo. oaooo. mmao. omooo. oomo. mmooo. mono. omsao><
mmooo. mmso. saooo. mono. msoco. oomo. smaoo. oooo. .a .a
ocooo. mmoo. moooo. mzmo. mmooo. oomo. moooo. ammo. .a .a
Amoebassae oav sew
ssm.oa mwm Omo.mss mom sao.om oom ama.ow was omsao><
aaa.om own Hmm.omfl mam mas.m sma sso.m Hmfi .o .a
ama.om awn www.mar mama oms.mma mm, saa.mom was .H .a
Ampcooom Cay ng
ooCmem> Cmoz ooCQHun> Emmi oocmmpm> 2mm: oocmflpm> Coo: monommoz oncogmom
ophq popcopxm kapmm HOLwcoo
szmzsamms so mmaomcm "mampmamz s:oHns aoom oz< mmzoamem so mmozawm<> nz< m:<az

 

ma. mo.a
:0. sq.
ma. os.H
a
F/ @mwom mm.”
ma.m am.s
om.w ma.s

Ma. 3H.H
SQ. m3 .
mm. mw.fi
m©.m .

so. am.
30. N:.
@m. am.H
3a.: Hm.n
m©.N 0:.N
mm.oa ma.w

oo.a

u
pm.a

owmpo><
oQ. cam
.H .m

 

Anasam say 822
omwso><
cg om
.H .m

 

AmEmhm cflv 33

 

mopzmaoz psmfloz Spom

 

ooCmHsm> Cmoz

ooCmHLm> Coo:

oocnflhw> coo:

oonHLm> smog

 

opmq

oooaooxm

zfipmm

HOppcoo

 

 

HZHEB<mmB wm mmHomgm

“mzmbm<mz RECHEE %Qom QZ< mmzommmm

ho meZQHm<> 924 mz<mz

A P P EN DI X C

 

 

 

 

om: Hmfi mma on am assos
mma mm ma m ma .6 .a
mam ms mma mo ma .s .a
we.
mmom mac smoa mmaa mos Hsooe
moom com saw coca om: .o .o
mmo msa maa m msm .H .a
18....
mmsm. ammo. mmso. ooso. mmfi. aseos
aaaa. Same. msoo. osmo. msmo. .o .a
/o mama. msmo. Osmo. mmo. ammo. .a .a
_, A.mE saw Ham
mommsnso momosmm msamssmm soassms mommwoom aspoa
mammmooa mommmm masmmsm mmomam Hmwomm .o .a
soaowosm mamssaa Hoooaomm asasmos msomosom .H .a
A.oon cap 69H
Hmuoe oumq popcopxm xflhmm Hohpcoo mohzmmoz oncoomom

 

 

coflpwpcoo onEpmohB

 

 

mmm<bam mo mzbm

 

 

 

 

ma.moa ac.wm ms.zm mm.sa mm.mm Hohoe
am.ofl mm.m rm.m mm.m sm.m .o .a
mm.am mc.mm ms.mm mo.ma mm.om .H .a
AmEmsm CHV U32
sm.mmsm os.amm Hm.mmw sm.waoa mfi.m®m assoe
mm.masa mm.msa om.mas om.css mm.mas .o .a
mm.mwma ms.mma Ho.wca so.msm ow.ama .H .a
Assets saw as
op: no: pgmfloz upom
Hmpoa opmd popcopxm zwumm aosLCoo

 

coapflpcoo pnoEpmoLE

 

 

mzm<bam

ho WEDQ

APPEI‘JDIX D

C'
s.)

.1
'1

CIL

-WITHIN SPE

C“

Ji‘J o

l
v
\

TDIVIDUAL COMPARIST”

Effli 1

zlLUth

[-

 

 

Body Weight Measures

ReSponse Measures

 

WG

P-p

)1“ )1);

TC TE

SET

ITD

Comparison

 

‘
L)

f T O 1”: L1 “:1

1eu

 

U) U) U)
C C1 C
U) U) U)
C. C. C.
U) U) U)
C C C.
C) U) U)
C C C
j) C) U)
9 a e' .
C) U) C)

SEC:

(DC)
Ill
<E<E<CC4

U)U)U)
CCC
CDC/)0)
{ICC
CDC-0U)
EEC.
[00).U)
CCC.
(CC/)6")
CCC
03090)
CCC
QDQQ

C40

ionotus

p01

 

01(0thin
CCCCCC

U)U)O)U)U)

mmmtotom
CCCCICJCI

U\
C)
J U) U) U) U) U)
Q o o o o o
C C1 C: C C
0‘
H
[—4
o '—{ o o o 0
U) Q U) U) U) U)
C V C C C, C
{1.
A
Of)
Li\ I,"
<3 0
C") '1'.) U) V C.,) V
o o o P a 11‘
C C C L.
0‘
(fl Cd
r—i r—1'
CD (I) Qr D Q Q

<E<lfl<ECJCQD

 

 

Late RPI.

Extended RPI D—

C-

O
Q
1

f

irly RPI

H 4
B— E

ment;

UV II'OH

HNormalH E

81

APPENDIX E

60

61

 

 

 

 

.o.c .o.e .o.c o.c .h.e moc.,t .ma.w
m.c .m.c .n.c .m.: .m.c .m.: aim
.m.c mo.vo .sm.a .a.e .m.c .m.s mo.vo .Ss.m o-m
.m.c .m.c .m.c .m.c :©.vo .wo.m .m.: Qn<
.m.e .n.s .m.a .n.: Ho.vo .mo.m moo.vo .wa.m o-<
.m.e mo.vo .oo.m .n.a .m.e mo.vo .om.m .m.c m-<
632 33 we on ham 69H comassano

 

mopSmwoz pnmfloz mpom

 

mohzmmoz omcoamwm

 

 

mmHommm mmomo<lumzomHm<mzoo Q<DQH>HQZH mom WMDQ<> N

APPENDIX E

MEAN

VALUES FOR MALE AND FEMALE

63

Ss

 

 

Treatment Condition

 

 

 

Measure A B c D

N212
ITD 620.78 451.67 972.10 154.50
SFT .0609 .0483 0340 0575
TC 4.44 7.67 7.40 6.25
TE .1.78 1.33 2.60 25
ww 7.56 8.03 7.37 7.91
NWG 1.22 .76 1.17 1.00

Female
ITD 286.29 402.25 787.33 676.00
SFT .0800 .0550 .0600 .0400
TC 7.29 5.50 4t83 3.25
TE 1.57 3.30 1.67 2.00
int 7.29 7.55 7.40 6.53
NWG .86 1.35 1.09 1.33

 

APPENDIX G

64

 

 

 

 

om: HMH wma 0% am Hmpoa
mma cw ma m ma .6 .a
mwm ma ama mm ma .a .a
My.
mmom mac smoa mafia mos asboe
ooom mom ago whoa 60: .a .6
who maa maa mm msm .H .m
um...
omsm. ammo. wmao. omso. mma. Capos
sasa. Samo. msoo. osmo. mswo. .o .a
/o mama. msmo. osmo. ommo. ammo. .a .a
C. /

CHE saw
mommsssm mooosmm msams mm aosssms mommwoom ssooe
msmomooa Smommmm masmmsc mmmmHm Homomm .o .a
scaomosm msmssaa Hmooaomm osssmos wsomoaom .H .a

A.oom say 65H
HmpoB opmq poocopxm xahmm Hohpcoo moCSmmoz ongoomom

 

coflpflpcoo pcoepmope

 

mmm<5®m ho mzbm

57

 

 

 

 

ma.moa Co.wm ms.am mm.sa mw.mm Capos
am.oa mm.m rm.m mm.m sm.m .o .a
mm.am mc.mm ms.mm mo.ma mm.om .H .a
AwEmsm QHV U32
sm.mmsm os.amm Hm.mmw sm.waoa ma.mmw aseos
mm.masa mm.msq om.mas om.mas mm.maa .o .a
mm.mmma ms.mma Ho.wos so.msm mm.ams .H .s
AmEmpo SHV 33
Mopzmmoz stfloz xpom
HmpoB opmq popcoax: xflumm Hoapcov

 

 

coppflpcoo pcoEpmoLE

 

mmm<58m

b0 mZDW

A PP EN DI X D

WITHIN SPECIES

C“
AJ—‘I/

EOR INDIVIDUAL COMPARISON

LIES

.‘\
n

[T

\

,r
/

PAAIUfl—DHIIIWIEY7 L

 

 

Body Weight Measures

Response Measures

 

IIWG

WW

TE

TC

SET

ITD

Comparison

 

m m main 6
CCCCCC
m m mCDUlm
QQCCCCI
m m mcoclm
CCCICCC:
m w mcoolm
CCCIGCICI
a a niacin
("CCCCIC
a m Quinta
:CCCCCI

 

Milo QCQCJQ
I I I I I I
<z< <Cflfllo

P. polionotus

 

m WCDUDW m
QCCCCC

U)U)U)U)U)U)

LI\
0
V U) U) U) U) U)
Q o o o o o
C1 C: C: C. C
0‘
H
H
o f——{ o o o 0
U) Q U) U) U) U)
C V C C. C: C
Cl.
OD
Lf\ {I-
C) O
u) ) U) V U) V
o o 0 L44 0 CL,
C: C. C: C
n 0x
m Cd
v—"I t—I

CJOQOQQ
llllll
<E<E<CQCQO

 

Extended RPI' D— Late RPI.

a- ”Early RPI; c-

)

i1” Environment

,
C.

Norm

H

APPENDIX E

60

61

 

 

 

 

m.c .m.c .n.c .m.c .m.: .m.: Gum
omoc moovg “Noon—H omog omoc omog mOoVQ «NS-m Olm
omog .mog smog owe: fiO-VQ «woom .moC QI<
.mog owoc .mog .mo: HO.VQ nM©.N NOO.VQ nmfiom Old
omog mOoVQ nooom .m.: .m.: mooVQ nwmcm omoq ml<
633 33 me oh Ham 63H comaasQEoo
moHSmmoz pcwwwz xpom moLSmmoz oncoamom

 

 

 

WMHommm mmomo<llmzomHm<mzoo Q<DQH>HQZH mom mmbq<> N

APPENDIX E

62

MEAN

63

VALUES FOR MALE AND FEMALE

 

 

Treatment Condition

 

 

 

Measure A B C D Total
N212
ITD 620.78 451.67 972.10 154 50 (43)
SFT .0609 .0483 0340 0575
TC 4.44 7.67 7.40 6.25
TE .1.78 1.33 2.60 2 25
ww 7.56 8.03 7.37 7.91
NWG 1.22 .76 1.17 1 00
Female
ITD 286 29 402.25 787.33 676.00 (21)
SFT .0800 0550 .0600 .0400
TC 7.29 5.50 4.83 3.25
TE 1.57 3.30 1.67 2.00
Ifli 7.29 7.55 7.40 6.53
NWG .86 1.35 1.09 1.33

 

APPENDIX G

65

MEAN VALUES FOR MALE AND FEMALE SS OF BOTH SPECIES

 

 

 

 

Measure _Species

Male - P. 1. P. p.
ITD 900.29 1256.68
SFT .0576 .0486
TC 3.90 9.05
TE 2.48 1.50
ini 7.96 7.54
WW 1 61 45

Female

ITD 460.45 517.60
SFT .0627 .0610
TC 3.45 7.70
TE 2.36 1.50
IflJ 7.53 6-89
NWG 1.56 .61