Classics in the History of Psychology
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Christopher D. Green
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The Nature of Love
Harry F. Harlow (1958)[1]
First published in American Psychologist, 13, 673-685
Posted March 2000
Address of the President at the sixty-sixth Annual Convention of the
American Psychological Association, Washington, D. C., August 31, 1958.
First published in American Psychologist, 13, 573-685.
Love is a wondrous state,
deep, tender, and rewarding. Because of its intimate and personal nature it is
regarded by some as an improper topic for experimental research. But, whatever
our personal feelings may be, our assigned mission as psychologists is to
analyze all facets of human and animal behavior into their component variables.
So far as love or affection is concerned, psychologists have failed in this
mission. The little we know about love does not transcend simple observation,
and the little we write about it has been written better by poets and
novelists. But of greater concern is the fact that psychologists tend to give
progressively less attention to a motive which pervades our entire lives.
Psychologists, at least psychologists who write textbooks, not only show no
interest in the origin and development of love or affection, but they seem to
be unaware of its very existence.
The apparent repression of
love by modem psychologists stands in sharp contrast with the attitude taken by
many famous and normal people. The word "love" has the highest
reference frequency of any word cited in Bartlett's book of Familiar
Quotations. It would appear that this emotion has long had a vast interest
and fascination for human beings, regardless of the attitude taken by
psychologists; but the quotations cited, even by famous and normal people, have
a mundane redundancy. These authors and authorities have stolen love from the
child and infant and made it the exclusive property of the adolescent and
adult.
Thoughtful men, and
probably all women, have speculated on the nature of love. From the
developmental point of view, the general plan is quite clear: The initial love
responses of the human being are those made by the infant to the mother or some
mother surrogate. From this intimate attachment of the child to the mother,
multiple learned and generalized affectional responses are formed.
Unfortunately, beyond these
simple facts we know little about the fundamental variables underlying the
formation of affectional responses and little about the mechanisms through
which the love of the infant for the mother develops into the multifaceted
response patterns characterizing love or affection in the adult. Because of the
dearth of experimentation, theories about the fundamental nature of affection
have evolved at the level of observation, intuition, and discerning guesswork,
whether these have been proposed by psychologists, sociologists,
anthropologists, physicians, or psychoanalysts.
The position commonly held
by psychologists and sociologists is quite clear: The basic motives are, for
the most part, the primary drives -- particularly hunger, thirst, elimination,
pain, and sex -- and all other motives, including love or affection, are
derived or secondary drives. The mother is associated with the reduction of the
primary drives -- particularly hunger, thirst, and pain -- and through
learning, affection or love is derived.
It is entirely reasonable
to believe that the mother through association with food may become a
secondary-reinforcing agent, but this is an inadequate mechanism to account for
the persistence of the infant-maternal ties. There is a spate of researches on
the formation of secondary reinforcers to hunger and thirst reduction. There
can be no question that almost any external stimulus can become a secondary
reinforcer if properly associated with tissue-need reduction, but the fact
remains that this redundant literature demonstrates unequivocally that such
derived drives suffer relatively rapid experimental extinction. Contrariwise,
human affection does not extinguish when the mother ceases to have intimate
association with the drives in question. Instead, the affectional ties to the
mother show a lifelong, unrelenting persistence and, even more surprising,
widely expanding generality.
Oddly enough, one of the
few psychologists who took a position counter to modern psychological dogma was
John B. Watson, who believed that love was an innate emotion elicited by
cutaneous stimulation of the erogenous zones. But experimental psychologists,
with their peculiar propensity to discover facts that are not true, brushed
this theory aside by demonstrating that the human neonate had no differentiable
emotions, and they established a fundamental psychological law that prophets
are without honor in their own profession.
The psychoanalysts have
concerned themselves with the problem of the nature of the development of love
in the neonate and infant, using ill and aging human beings as subjects. They
have discovered the overwhelming importance of the breast and related this to
the oral erotic tendencies developed at an age preceding their subjects'
memories. Their theories range from a belief that the infant has an innate need
to achieve and suckle at the breast to beliefs not unlike commonly accepted
psychological theories. There are exceptions, as seen in the recent writings of
John Bowlby, who attributes importance not only to food and thirst
satisfaction, but also to "primary object-clinging," a need for
intimate physical contact, which is initially associated with the mother.
As far as I know, there
exists no direct experimental analysis of the relative importance of the
stimulus variables determining the affectional or love responses in the
neonatal and infant primate. Unfortunately, the human neonate is a limited
experimental subject for such researches because of his inadequate motor
capabilities. By the time the human infant's motor responses can be precisely
measured, the antecedent determining conditions cannot be defined, having been
lost in a jumble and jungle of confounded variables.
Many of these difficulties
can be resolved by the use of the neonatal and infant macaque monkey as the
subject for the analysis of basic affectional variables. It is possible to make
precise measurements in this primate beginning at two to ten days of age,
depending upon the maturational status of the individual animal at birth. The
macaque infant differs from the human infant in that the monkey is more mature
at birth and grows more rapidly; but the basic responses relating to affection,
including nursing, contact, clinging, and even visual and auditory exploration,
exhibit no fundamental differences in the two species. Even the development of
perception, fear, frustration, and learning capability follows very similar
sequences in rhesus monkeys and human children.
Three years'
experimentation before we started our studies on affection gave us experience
with the neonatal monkey. We had separated more than 60 of these animals from
their mothers 6 to 12 hours after birth and suckled them on tiny bottles. The
infant mortality was only a small fraction of what would have obtained had we
let the monkey mothers raise their infants. Our bottle-fed babies were
healthier and heavier than monkey-mother-reared infants. We know that we are
better monkey mothers than are real monkey mothers thanks to synthetic diets,
vitamins, iron extracts, penicillin, chloromycetin, 5% glucose, and constant, tender,
loving care.
During the course of these
studies we noticed that the laboratory raised babies showed strong attachment
to the cloth pads (folded gauze diapers) which were used to cover the
hardware-cloth floors of their cages. The infants clung to these pads and
engaged in violet temper tantrums when the pads were removed and replaced for
sanitary reasons. Such contact-need or responsiveness had been reported
previously by Gertrude van Wagenen for the monkey and by Thomas McCulloch and
George Haslerud for the chimpanzee and is reminiscent of the devotion often
exhibited by human infants to their pillows, blankets, and soft, cuddly stuffed
toys. Responsiveness by the one-day-old infant monkey to the cloth pad is shown
in Figure 1, and an unusual and strong attachment of a six-month-old infant to
the cloth pad is illustrated in Figure 2. The baby, human or monkey, if it is
to survive, must clutch at more than a straw.
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We had also discovered during some allied
observational studies that a baby monkey raised on a bare wire-mesh cage floor
survives with difficulty, if at all, during the first five days of life. If a
wire-mesh cone is introduced, the baby does better; and, if the cone is covered
with terry cloth, husky, healthy, happy babies evolve. It takes more than a
baby and a box to make a normal monkey. We were impressed by the possibility that,
above and beyond the bubbling fountain of breast or bottle, contact comfort
might be a very important variable in the development of the infant's affection
for the mother.
At this point we decided to
study the development of affectional responses of neonatal and infant monkeys
to an artificial, inanimate mother, and so we built a surrogate mother which we
hoped and believed would be a good surrogate mother. In devising this surrogate
mother we were dependent neither upon the capriciousness of evolutionary
processes nor upon mutations produced by chance radioactive fallout. Instead,
we designed the mother surrogate in terms of modem human engineering principles
(Figure 3). We produced a perfectly proportioned, streamlined body stripped of
unnecessary bulges and appendices. Redundancy in the surrogate mother's system
was avoided by reducing the number of breasts from two to one and placing this
unibreast in an upper-thoracic, sagittal position, thus maximizing the natural
and known perceptual-motor capabilities of the infant operator. The surrogate
was made from a block of wood, covered with sponge rubber, and sheathed in tan
cotton terry cloth. A light bulb behind her radiated heat. The result was a
mother, soft, warm, and tender, a mother with infinite patience, a mother
available twenty-four hours a day, a mother that never scolded her infant and
never struck or bit her baby in anger. Furthermore, we designed a
mother-machine with maximal maintenance efficiency since failure of any system
or function could be resolved by the simple substitution of black boxes and new
component parts. It is our opinion that we engineered a very superior monkey
mother, although this position is not held universally by the monkey fathers.
Before beginning our initial experiment we also
designed and constructed a second mother surrogate, a surrogate in which we
deliberately built less than the maximal capability for contact comfort. This
surrogate mother is illustrated in Figure 4. She is made of wire-mesh, a
substance entirely adequate to provide postural support and nursing capability,
and she is warmed by radiant heat. Her body differs in no essential way from
that of the cloth mother surrogate other than in the quality of the contact
comfort which she can supply. In our initial experiment, the dual
mother-surrogate condition, a cloth mother and a wire mother were placed in
different cubicles attached to the infant's living cage as shown in Figure 4.
For four newborn monkeys the cloth mother lactated and the wire mother did not;
and, for the other four, this condition was reversed. In either condition the
infant received all its milk through the mother surrogate as soon as it was
able to maintain itself in this way, a capability achieved within two or three
days except in the case of very immature infants. Supplementary feedings were
given until the milk intake from the mother surrogate was adequate. Thus, the
experiment was designed as a test of the relative importance of the variables
of contact comfort and nursing comfort. During the first 14 days of life the
monkey's cage floor was covered with a heating pad wrapped in a folded gauze
diaper, and thereafter the cage floor was bare. The infants were always free to
leave the heating pad or cage floor to contact either mother, and the time
spent on the surrogate mothers was automatically recorded. Figure 5 shows the
total time spent cloth and wire mothers under the two conditions of feeding.
These data make it obvious that contact comfort is a variable of overwhelming
importance in the development of affectional response, whereas lactation is a
variable of negligible importance. With age and opportunity to learn, subjects
with the lactating wire mother showed decreasing responsiveness to her and
increasing responsiveness to the nonlactating cloth mother, a finding
completely contrary to any interpretation of derived drive in which the
mother-form becomes conditioned to hunger-thirst reduction. The persistence of
these differential responses throughout 165 consecutive days of testing is
evident in Figure 6.
One control group of
neonatal monkeys was raised on a single wire mother, and a second control group
was raised on a single cloth mother. There were no differences between these
two groups in amount of milk ingested or in weight gain. The only difference
between the two groups lay in the composition of the feces, the softer stools
of the wire-mother infants suggesting psychosomatic involvement. The wire
mother is biologically adequate but psychologically inept.
We were not surprised to discover
that contact comfort was an important basic affectional or love variable, but
we did not expect it to overshadow so completely the variable of nursing;
indeed; indeed, the disparity is so great as to suggest that the primary
function of nursing as an affectional variable is that of insuring frequent and
intimate body contact of the infant with the mother. Certainly, man cannot live
by milk alone. Love is an emotion that does not need to be bottle- or
spoon-fed, and we may be sure that there is nothing to be gained by giving lip
service to love.
A charming lady once heard
me describe these experiments and, when I subsequently talked to her, her face
brightened with sudden insight: "Now I know what's wrong with me,"
she said, "I'm just a wire mother." Perhaps she was lucky. She might
have been a wire wife.
We believe that contact
comfort has long served the animal kingdom as a motivating agent for
affectional responses. Since at the present time we have no experimental data
to substantiate this position, we supply information which must be accepted, if
at all, on the basis of face validity:
One function of the real
mother, human or subhuman, and presumably of a mother surrogate, is to provide
a haven of safety for the infant in times of fear and danger. The frightened or
ailing child clings to its mother, not its father; and this selective
responsiveness in times of distress, disturbance, or danger may be used as a
measure of the strength of affectional bonds. We have tested this kind of differential
responsiveness by presenting to the infants in their cages, in the presence of
the two mothers, various fear-producing stimuli such as the moving toy bear
illustrated in Figure 13. A typical response to a fear stimulus is shown in
Figure 14, and the data on differential responsiveness are presented in Figure
15. It is apparent that the cloth mother is highly preferred over the wire one,
and this differential selectivity is enhanced by age and experience. In this
situation, the variable of nursing appears to be of absolutely no importance:
the infant consistently seeks the soft mother surrogate regardless of nursing
condition.
Similarly, the mother or
mother surrogate provides its young with a source of security, and this role or
function is seen with special clarity when mother and child are in a strange
situation. At the present time we have completed tests for this relationship on
four of our eight baby monkeys assigned to the dual mother-surrogate condition
by introducing them for three minutes into the strange environment of a room
measuring six feet by six feet by six feet (also called the "open-field
test") and containing multiple stimuli known to elicit
curiosity-manipulatory responses in baby monkeys. The subjects were placed in
this situation twice a week for eight weeks with no mother surrogate present
during alternate sessions and the cloth mother present during the others. A
cloth diaper was always available as one of the stimuli throughout all
sessions. After one or two adaptation sessions, the infants always rushed to
the mother surrogate when she was present and clutched her, rubbed their bodies
against her, and frequently manipulated her body and face. After a few
additional sessions, the infants began to use the mother surrogate as a source
of security, a base of operations. As is shown in Figures 16 and 17, they would
explore and manipulate a stimulus and then return to the mother before
adventuring again into the strange new world. The behavior of these infants was
quite different when the mother was absent from the room. Frequently they would
freeze in a crouched position, as is illustrated in Figures 18 and 19.
Emotionality indices such as vocalization, crouching, rocking, and sucking
increased sharply, as shown in Figure 20. Total emotionality score was cut in
half when the mother was present. In the absence of the mother some of the
experimental monkeys would rush to the center of the room where the mother was
customarily placed and then run rapidly from object to object, screaming and
crying all the while. Continuous, frantic clutching of their bodies was very
common, even when not in the crouching position. These monkeys frequently
contacted and clutched the cloth diaper, but this action never pacified them.
The same behavior occurred in the presence of the wire mother. No difference
between the cloth-mother-fed and wire-mother-fed infants was demonstrated under
either condition. Four control infants never raised with a mother surrogate
showed the same emotionality scores when the mother was absent as the
experimental infants showed in the absence of the mother, but the controls'
scores were slightly larger in the presence of the mother surrogate than in her
absence.
Some years ago Robert Butler demonstrated that
mature monkeys enclosed in a dimly lighted box would open and reopen a door
hour after hour for no other reward than that of looking outside the box. We
now have data indicating that neonatal monkeys show this same compulsive visual
curiosity on their first test day in an adaptation of the Butler apparatus
which we call the "love machine," an apparatus designed to measure
love. Usually these tests are begun when the monkey is 10 days of age, but this
same persistent visual exploration has been obtained in a three-day-old monkey
during the first half-hour of testing. Butler also demonstrated that rhesus
monkeys show selectivity in rate and frequency of door-opening to stimuli of
differential attractiveness in the visual field outside the box. We have
utilized this principle of response selectivity by the monkey to measure
strength of affectional responsiveness in our infants in the baby version of
the Butler box. The test sequence involves four repetitions of a test battery
in which four stimuli -- cloth mother, wire mother, infant monkey, and empty
box -- are presented for a 30-minute period on successive days. The first four
subjects in the dual mother-surrogate group were given a single test sequence
at 40 to 50 days of age, depending upon the availability of the apparatus, and
only their data are presented. The second set of four subjects is being given
repetitive tests to obtain information relating to the development of visual
exploration. The apparatus is illustrated in Figure 21. The data obtained from
the first four infants raised with the two mother surrogates are presented in
the middle graph of Figure 22 and show approximately equal responding to the
cloth mother and another infant monkey, and no greater responsiveness to the
wire mother than to an empty box. Again, the results are independent of the
kind of mother that lactated, cloth or wire. The same results are found for a
control group raised, but not fed, on a single cloth mother; these data appear
in the graph on the right. Contrariwise, the graph on the left shows no
differential responsiveness to cloth and wire mothers by a second control
group, which was not raised on any mother surrogate. We can be certain that not
all love is blind.
The first four infant
monkeys in the dual mother-surrogate group were separated from their mothers
between 165 and 170 days of age and tested for retention during the following 9
days and then at 30-day intervals for six successive months. Affectional
retention as measured by the modified Butler box is given in Figure 23. In
keeping with the data obtained on adult monkeys by Butler, we find a high rate
of responding to any stimulus, even the empty box. But throughout the entire
185-day retention period there is a consistent and significant difference in
response frequency to the cloth mother contrasted with either the wire mother
or the empty box, and no consistent difference between wire mother and empty box.
Affectional retention was
also tested in the open field during the first 9 days after separation and then
at 30-day intervals, and each test condition was run twice at each retention
interval. The infant's behavior differed from that observed during the period
preceding separation. When the cloth mother was present in the post-separation
period, the babies rushed to her, climbed up, clung tightly to her, and rubbed
their heads and faces against her body. After this initial embrace and reunion,
they played on the mother, including biting and tearing at her cloth cover; but
they rarely made any attempt to leave her during the test period, nor did they
manipulate or play with the objects in the room, in contrast with their
behavior before maternal separation. The only exception was the occasional
monkey that left the mother surrogate momentarily, grasped the folded piece of
paper (one of the standard stimuli in the field), and brought it quickly back
to the mother. It appeared that deprivation had enhanced the tie to the mother
and rendered the contact-comfort need so prepotent that need for the mother
overwhelmed the exploratory motives during the brief, three-minute test
sessions. No change in these behaviors was observed throughout the 185-day
period. When the mother was absent from the open field, the behavior of the
infants was similar in the initial retention test to that during the
preseparation tests; but they tended to show gradual adaptation to the
open-field situation with repeated testing and, consequently, a reduction in
their emotionality scores.
In the last five retention
test periods, an additional test was introduced in which the surrogate mother
was placed in the center of the room and covered with a clear Plexiglas box.
The monkeys were initially disturbed and frustrated when their explorations and
manipulations of the box failed to provide contact with the mother. However,
all animals adapted to the situation rather rapidly. Soon they used the box as
a place of orientation for exploratory and play behavior, made frequent
contacts with the objects in the field, and very often brought these objects to
the Plexiglas box. The emotionality index was slightly higher than in the
condition of the available cloth mothers, but it in no way approached the
emotionality level displayed when the cloth mother was absent. Obviously, the
infant monkeys gained emotional security by the presence of the mother even
though contact was denied.
Affectional retention has
also been measured by tests in which the monkey must unfasten a three-device
mechanical puzzle to obtain entrance into a compartment containing the mother
surrogate. All the trials are initiated by allowing the infant to go through an
unlocked door, and in half the trials it finds the mother present and in half,
an empty compartment. The door is then locked and a ten-minute test conducted.
In tests given prior to separation from the surrogate mothers, some of the
infants had solved this puzzle and others had failed. The data of Figure 24
show that on the last test before separation there were no differences in total
manipulation under mother-present and mother-absent conditions, but striking
differences exist between the two conditions throughout the post-separation
test periods. Again, there is no interaction with conditions of feeding.
The over-all picture
obtained from surveying the retention data is unequivocal. There is little, if
any, waning of responsiveness to the mother throughout this five-month period
as indicated by any measure. It becomes perfectly obvious that this affectional
bond is highly resistant to forgetting and that it can be retained for very
long periods of time by relatively infrequent contact reinforcement. During the
next year, retention tests will be conducted at 90-day intervals, and further
plans are dependent upon the results obtained. It would appear that affectional
responses may show as much resistance to extinction as has been previously
demonstrated for learned fears and learned pain, and such data would be in
keeping with those of common human observation.
The infant's responses to
the mother surrogate in the fear tests, the open-field situation, and the baby
Butler box and the responses on the retention tests cannot be described
adequately with words. For supplementary information we turn to the motion
picture record. (At this point a 20-minute film was presented illustrating and
supplementing the behaviors described thus far in the address.)
We have already described
the group of four control infants that had never lived in the presence of any
mother surrogate and had demonstrated no sign of affection or security in the
presence of the cloth mothers introduced in test sessions. When these infants
reached the age of 250 days, cubicles containing both a cloth mother and a wire
mother were attached to their cages. There was no lactation in these mothers,
for the monkeys were on a solid-food diet. The initial reaction of the monkeys
to the alterations was one of extreme disturbance. All the infants screamed
violently and made repeated attempts to escape the cage whenever the door was
opened. They kept a maximum distance from the mother surrogates and exhibited a
considerable amount of rocking and crouching behavior, indicative of
emotionality. Our first thought was that the critical period for the
development of maternally directed affection had passed and that these macaque
children were doomed to live as affectional orphans. Fortunately, these
behaviors continued for only 12 to 48 hours and then gradually ebbed, changing
from indifference to active contact on, and exploration of, the surrogates. The
home-cage behavior of these control monkeys slowly became similar to that of
the animals raised with the mother surrogates from birth. Their manipulation
and play on the cloth mother became progressively more vigorous to the point of
actual mutilation, particularly during the morning after the cloth mother had
been given her daily change of terry covering. The control subjects were now
actively running to the cloth mother when frightened and had to be coaxed from
her to be taken from the cage for formal testing.
Objective evidence of these
changing behaviors is given in Figure 25, which plots the amount of time these
infants spent on the mother surrogates. Within 10 days mean contact time is
approximately nine hours, and this measure remains relatively constant
throughout the next 30 days. Consistent with the results on the subjects reared
from birth with dual mothers, these late-adopted infants spent less than one
and one-half hours per day in contact with the wire mothers, and this activity
level was relatively constant throughout the test sessions. Although the
maximum time that the control monkeys spent on the cloth mother was only about
half that Spent by the original dual mother-surrogate group, we cannot be sure
that this discrepancy is a function of differential early experience. The
control monkeys were about three months older when the mothers were attached to
their cages than the experimental animals had been when their mothers were
removed and the retention tests begun. Thus, we do not know what the amount of
contact would be for a 250-day-old animal raised from birth with surrogate
mothers. Nevertheless, the magnitude of the differences and the fact that the
contact-time curves for the mothered-from-birth infants had remained constant
for almost 150 days suggest that early experience with the mother is a variable
of measurable importance.
The control group has also
been tested for differential visual exploration after the introduction of the
cloth and wire mothers; these behaviors are plotted in Figure 26. By the second
test session a high level of exploratory behavior had developed, and the
responsiveness to the wire mother and the empty box is significantly greater
than that to the cloth mother. This is probably not an artifact since there is
every reason to believe that the face of the cloth mother is a fear stimulus to
most monkeys that have not had extensive experience with this object during the
first 40 to 60 days of life. Within the third test session a sharp change in
trend occurs, and the cloth mother is then more frequently viewed than the wire
mother or the blank box; this trend continues during the fourth session,
producing a significant preference for the cloth mother.
Before the introduction of
the mother surrogate into the home-cage situation, only one of the four control
monkeys had ever contacted the cloth mother in the open-field tests. In
general, the surrogate mother not only gave the infants no security, but
instead appeared to serve as a fear stimulus. The emotionality scores of these
control subjects were slightly higher during the mother-present test sessions
than during the mother-absent test sessions. These behaviors were changed
radically by the fourth post-introduction test approximately 60 days later. In
the absence of the cloth mothers the emotionality index in this fourth test
remains near the earlier level, but the score is reduced by half when the
mother is present, a result strikingly similar to that found for infants raised
with the dual mother-surrogates from birth. The control infants now show
increasing object exploration and play behavior, and they begin to use the
mother as a base of operations, as did the infants raised from birth with the mother
surrogates. However, there are still definite differences in the behavior of
the two groups. The control infants do not rush directly to the mother and
clutch her violently; but instead they go toward, and orient around, her,
usually after an initial period during which they frequently show disturbed
behavior, exploratory behavior, or both.
That the control monkeys
develop affection or love for the cloth mother when she is introduced into the
cage at 250 days of age cannot be questioned. There is every reason to believe,
however, that this interval of delay depresses the intensity of the affectional
response below that of the infant monkeys that were surrogate-mothered from
birth onward. In interpreting these data it is well to remember that the control
monkeys had had continuous opportunity to observe and hear other monkeys housed
in adjacent cages and that they had had limited opportunity to view and contact
surrogate mothers in the test situations, even though they did not exploit the
opportunities.
During the last two years
we have observed the behavior of two infants raised by their own mothers. Love
for the real mother and love for the surrogate mother appear to be very
similar. The baby macaque spends many hours a day clinging to its real mother. If
away from the mother when frightened, it rushes to her and in her presence
shows comfort and composure. As far as we can observe, the infant monkey's
affection for the real mother is strong, but no stronger than that of the
experimental monkey for the surrogate cloth mother, and the security that the
infant gains from the presence of the real mother is no greater than the
security it gains from a cloth surrogate. Next year we hope to put this problem
to final, definitive, experimental test. But, whether the mother is real or a
cloth surrogate, there does develop a deep and abiding bond between mother and
child. In one case it may be the call of the wild and in the other the McCall
of civilization, but in both cases there is "togetherness."
In spite of the importance
of contact comfort, there is reason to believe that other variables of
measurable importance will be discovered. Postural support may be such a
variable, and it has been suggested that, when we build arms into the mother
surrogate, 10 is the minimal number required to provide adequate child care.
Rocking motion may be such a variable, and we are comparing rocking and
stationary mother surrogates and inclined planes. The differential
responsiveness to cloth mother and cloth-covered inclined plane suggests that
clinging as well as contact is an affectional variable of importance. Sounds,
particularly natural, maternal sounds, may operate as either unlearned or
learned affectional variables. Visual responsiveness may be such a variable,
and it is possible that some semblance of visual imprinting may develop in the
neonatal monkey. There are indications that this becomes a variable of
importance during the course of infancy through some maturational process.
John Bowlby has suggested
that there is an affectional variable which he calls "primary object
following," characterized by visual and oral search of the mother's face.
Our surrogate-mother-raised baby monkeys are at first inattentive to her face,
as are human neonates to human mother faces. But by 30 days of age
ever-increasing responsiveness to the mother's face appears -- whether through
learning, maturation, or both -- and we have reason to believe that the face
becomes an object of special attention.
Our first
surrogate-mother-raised baby had a mother whose head was just a ball of wood
since the baby was a month early and we had not had time to design a more
esthetic head and face. This baby had contact with the blank-faced mother for
180 days and was then placed with two cloth mothers, one motionless and one
rocking, both being endowed with painted, ornamented faces. To our surprise the
animal would compulsively rotate both faces 180 degrees so that it viewed only
a round, smooth face and never the painted, ornamented face. Furthermore, it
would do this as long as the patience of the experimenter in reorienting the
faces persisted. The monkey showed no sign of fear or anxiety, but it showed
unlimited persistence. Subsequently it improved its technique, compulsively
removing the heads and rolling them into its cage as fast as they were
returned. We are intrigued by this observation, and we plan to examine
systematically the role of the mother face in the development of infant-monkey
affections. Indeed, these observations suggest the need for a series of
ethological-type researches on the two-faced female.
Although we have made no
attempts thus far to study the generalization of infant-macaque affection or
love, the techniques which we have developed offer promise in this uncharted
field. Beyond this, there are few if any technical difficulties in studying the
affection of the actual, living mother for the child, and the techniques
developed can be utilized and expanded for the analysis and developmental study
of father-infant and infant-infant affection.
Since we can measure
neonatal and infant affectional responses to mother surrogates, and since we
know they are strong and persisting, we are in a position to assess the effects
of feeding and contactual schedules; consistency and inconsistency in the
mother surrogates; and early, intermediate, and late maternal deprivation.
Again, we have here a family of problems of fundamental interest and
theoretical importance.
If the researches completed
and proposed make a contribution, I shall be grateful; but I have also given
full thought to possible practical applications. The socioeconomic demands of
the present and the threatened socioeconomic demands of the future have led the
American woman to displace, or threaten to displace, the American man in
science and industry. If this process continues, the problem of proper
child-rearing practices faces us with startling clarity. It is cheering in view
of this trend to realize that the American male is physically endowed with all
the really essential equipment to compete with the American female on equal
terms in one essential activity: the rearing of infants. We now know that women
in the working classes are not needed in the home because of their primary
mammalian capabilities; and it is possible that in the foreseeable future
neonatal nursing will not be regarded as a necessity, but as a luxury ---to use
Veblen's term -- a form of conspicuous consumption limited perhaps to the upper
classes. But whatever course history may take, it is comforting to know that we
are now in contact with the nature of love.
Footnote
[1] The
researches reported in this paper were supported by funds supplied by Grant No.
M-722, National Institutes of Health, by a grant from the Ford Foundation, and
by funds received from the Graduate School of the University of Wisconsin.