Experimental studies involving infant separation of monkeys from their mothers was started by Dr. Harry Harlow, a Behavioral Primatologist Psychologist at the University of Wisconsin and Director of the Regional Primate Center there. He was attempting to develop a breeding colony for experimental research with these animals. So he, for whatever reason, decided that it was a good idea to separate the infants from the mothers and rear them in cages by themselves. It wasn’t until some time later that he noticed that these animals were engaged in a very emotionally, socially, abnormal, bizarre behaviors.
Film: Psychologist Harry Harlow at the University of Wisconsin has long studied the importance of the early experience of infant monkeys. Whether the cloth dummies or wire dummies contained milk, the monkeys preferred the cloth covered mother substitutes at all times. The isolated monkeys would spend as much as 15 hours a day clinging to their cloth mothers. And this attachment persisted after a separation as long as two years. When the clot mother was removed the monkeys showed signs of extreme disturbance. But they were calmed and comforted when the mother was returned. The wire substitute even when it held a bottle, excited no affection in the monkeys. The apparent apathy of this animal and it rocking behavior became an important focus for later study. Dr. Harlow is still investigating the depression that follows the separation of young monkeys from it mother. Dr. Harlow says his work began as a mishap. He was raising single monkeys in separate cages when John Bowlby suggested that he was really raising a collection of abnormal monkeys.
In fact it was John Bowlby, the English Psychiatrist, who made major contributions on the effects of maternal deprivation, emotional deprivation methods of children, infants being separated from their mothers, who informed him that you were raising abnormal animals like we see in children in orphanages and so forth. And as the animals grew older they were sexually dysfunctional and they were pathologically violent. They engaged in self-mutilation and essentially homicidal assaults against younger animals and even older animals, juvenile animals who were isolation reared, engaged in behavior that no normal juvenile monkey would do, like attacking a big huge alpha male. I mean no juvenile monkey in their right mind does this. But these would. So there’s no, the normal constraints on a normal aggression was gone.
Well when I joined the National Institute of Child Health and Human Development, one of the National Institutes of Health in Bethesda, Maryland, I was brought on board to create the developmental behavioral biology program, to look at brain behavioral studies, the effects of early experiences on brain development behavior, and to examine what were the most crucial issues for child healthy human development. And one of the issues was child abuse and neglect, the effects of eternal social deprivation, which had occupied developmental psychologists for a long time. And what remained was the enigma of understanding these pathological emotional behaviors and social behaviors of these isolation reared monkeys.
And what caught my attention was the denial of Dr. Harlow, that these separation experiences involved sensory deprivation. Rene Spitz, a Psycho Analyst, made the same statement about his studies on infants who were institutionalized or hospitalized, where they received no touching, reared in cribs, no physical contact but physical care and medical care was more than adequate. And many of these infants would develop depression, a found withdrawal, and some even died. But even Rene Spitz denied that this involved sensory deprivation. And so these two individuals in my view historically mislead the entire field for almost a generation.
And as a Developmental Neural Psychologist I said this is craziness. This is impossible. The only way an infant communicates with its environment, mother and everyone else, and anything else in the environment, is through our sensory systems. So it has to involve our sensory systems. So the question is which sensory systems are the most important?
Probably the most significant of the primate isolation rearing studies next to the Harlow’s original contributions was that conducted by William Mason and Gersh Berkson who were, Dr. Mason was also at Harlow’s Laboratory in which he reared isolation reared infant monkeys on a swinging mother surrogate and another group who reared on a stationary mother surrogate. Low and behold what happens is that this infant monkey that was sitting on this swinging mother surrogate did not develop any of the emotional social psycho pathologies. There was not the depression, the withdrawal behavior, the autistic life behaviors, the rocking behaviors, self-stimulation behaviors, nor the pathological violence when they grew up as juveniles and adults. They had no tactile aversion which the infant monkeys who were reared on the stationary surrogate had developed.
Film: This swinging substitute mother a bleach bottle covered with flurry cloth was invented for an experiment by Doctors William Mason and Gersh Berkson at the delta primate center in Louisiana. The isolated monkey has known no other mother than this moving surrogate which rises and falls and sways in a random way. This isolated monkey has an identical surrogate mother, but the mother does not move. At ten months of age the monkey raised on the moving surrogate substitute is given a chance to make close physical contact with a human being. His behavior seems normal. He appears to be curious, bold, and friendly. The monkey raised on the stationary mother behaves in quite a different way. He seems timid, cringing and apparently unhappy. He appears emotionally disturbed and unresponsive to changes in the environment. Rocking and other abnormal behavior were prevented in the monkey with the swinging surrogate. The monkey on the stationary surrogate displays the familiar stereotype rocking movements.
So what this study indicated was another sensory system, was of crucial importance, in fact more important than just touch and that’s the sensory system that mediates motion, movement, and that’s the vestibular cerebella system. And when you look back on it and you look at what happens in-utero, the dominant sensory system is one of motion, of movement. Of all the six sensory systems, the one that’s continually being stimulated is the movement, with the mother moving around all day long. Vision, hearing, smell, touch, taste are essentially non-functional, not entirely but essentially non-functional. So the continuity, the psychological continuity of this motion which the fetus is continually developing in contact with its mother, the most important sensory modality is movement. In many cultures and ours this movement stimulation ends and this has to be sensory deprivation. That’s shock. And clearly it seemed to me that this was a major ingredient to understanding the depression, the alienation and the violence in human populations.