Psychosomatic Medicine 21:353-378 (1959)
© 1959 American Psychosomatic Society

Infantile Experience and Adult Behavior in Animal Subjects

II. Age of Separation from the Mother and Adult Behavior in the Cat

¹ Institute for Psychoanalysis, Chicago

Employing the split-litter technique, the kittens from several litters of non-isogenic cats were divided into 3 experimental groups. Group I kittens were separated from their mothers at 2 weeks of age, which is early in this species and causes intense "crying" for as long as a week or more. Group II kittens were separated from their mothers when they were found to have begun lapping milk spontaneously from saucers. This usually occurred at around 6 weeks of age. Group III kittens were forced to go on suckling for 12 weeks, by making no food other than the mother's milk available to them. At 12 weeks of age they were removed from their mothers.

Following separation from their mothers, the kittens in all 3 experimental groups were placed in identical, individual living cages, and their life experiences were standardized. When they reached adulthood, a series of behavioral tests were made. These tests revealed that Group I animals, removed from their mothers at 2 weeks of age, were the most randomly active, but showed the least goal-directed movements throughout their lives. They were the most anxious in novel situations. They were the most disturbed by and slowest to recover from intense stimulation. They were the most persistent but also most disorganized in their efforts to get food when hungry and frustrated. They were the most aggressive but least successful in feeding competitions. They had the least tendency to share food. They were the slowest to learn a simple feeding routine; but they were the least susceptible to severe, generalized feeding inhibitions in response to feeding conflict.

Throughout their lives the Group I animals were more suspicious, fearful and aggressive in their behavior toward other cats and toward the experimenters. Following the feeding frustration tests, 2 of the Group I cats developed a chronic, asthma-like, respiratory wheezing syndrome that veterinary consultants were unable to diagnose. The condition had certain similarities to bronchial asthma in humans, raising the question whether the cat might be a useful experimental animal for psychosomatic research in asthma.

The findings of the present experiment follow the same general patterns and principles that were found to apply in other experiments of this series. Early infantile traumata have persistent effects upon adult behavior, lasting throughout the lifetime of the animal and affecting practically every modality of behavior that is tested. These findings correspond with a principle of development discovered in experimental embryology: the earlier a trauma occurs in the development of an organism, the greater the number of structures that are affected by it.

The specific findings of this experiment have been discussed separately in some detail.

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