Jerome Kagan, who is a professor of psychology at Harvard, is recognized as one of the world’s leading experts on child development. In this well-written, fascinating book, he summarizes what is now known about the psychological development of the child from infancy onward, and in doing so he challenges many current assumptions about the family and its influence.

throughout the book, Kagan’s emphasis is on the interaction between biology and experience. However well endowed a child may be genetically, his brain will not develop its full potential unless he is exposed to stimulation and the opportunity to act. Moreover, from the very earliest days, there is competition between brain cells. “If the right hand is used more than the left, the neural connections that serve the right hand expand their sphere of dominance; those serving the left lose some power.”

Kagan begins by considering the human infant, remarking that “the properties of the infant are so distinct from those of the older child that it is not surprising that all societies regard the first two years of life as a special period of development.” But what is emphasized, or indeed assumed, as being universally true about infants is shown by Kagan to depend upon historical and cultural factors which are highly variable. Thus Melanie Klein’s attribution of extremely aggressive impulses to the infant was formulated during the 1930s; when control of childhood aggression was a major preoccupation of Western society. “Since the Second World War, childhood aggression has become more acceptable and, accordingly, Klein’s description has become obsolete.” Whereas psychoanalysts have stressed the supporsed course of emotional development in the infant, Kagan emphasizes cognitive development, and shows that in many instances the capacity to experience emotions depends upon the prior development of cognitive potential.

Modern research into the capacities of infants is fascinatingly ingenious. Even newborn babies can be shown to develop schemata; that is, representations of experence that are stored in the brain and that remain as standards against which subsequent experiences can be evaluated. Like adults, infants pay more attention to the unexpected and unfamiliar. Learning depends upon noticing and assimilating discrepancy; but discrepancies which are too great, and which therefore cannot be assimilated, generate uncertainty and then anxiety. In the second half of the first year, infants commonly exhibit fear of unfamiliar adults, and fear of separation from their mothers. Kagan maintains that the development of these fears depends upon the development of the infant’s cognitive capacities rather than upon the quality of his relation with the mother. that is, it is only when the infant has become able to compare his schema of the mother with the unfamiliar appearance of the stranger that anxiety occurs; and this argues a considerable development of memory and the power of retrieval of previously received information.

IN SIMILAR fashion, the fact that separation anxiety tends to decrease from about the age of 2 depends upon the child having developed the cognitive capacity for understanding the significance of the mother’s departure and upon having gamed the knowledge that she will return. although Kagan does not dispute the importance of “secure attachment” to the mother or other caretakers in early childhood, he suggests that our present preoccupation with this theme may be overdone. It is by no means proven that vulnerability to anxiety is related to the presence or absence of “secure attachment” in early infancy. temperamental differences between infants can be demonstrated from the earliest days after birth, before there can be any question of attachment having developed. What Kagan calls “inhibition to the unfamiliar,” that is, shyness, caution, and timidity, can be detected as early as 8 months and remains a persistent trait into later childhood. Inhibited children are more irritable, more prone to constipation, and more likely to show allergic responses–”symptoms that reflect a higher level of physiological response to everyday events.” Although Kagan does not mention it, there is an obvious link here with Hans Eysenck’s delineation of introversion and neuroticism, which eysenck supposes to be much more dependent upon genetic than upon environmental factors.

I was deligated to note that Kagan throws doubt upon the existence of “general intelligence.” I predict that within the next decade we shall see the disappearance of the notion of I.Q. in favor of the recognition that different kinds of intelligence exist which are not necessarily closely related. Kagan quotes an experiment in which it was shown that many backward readers were just as quick at deciding the truth or falsity of certain oral statements as those who could read more fluently. Kagan also accepts that, although most creative children are intelligent, intelligent children are not necessarily creative. One characteristic of the creative person is “some indifference to the humiliation that can follow making a mistake.”

One of Kagan’s most interesting chapters is on “Connectedness.” As he observes, the pervasive assumption is that the effects of early emotional experience are permanent, that stages in development succeed one another and cannot be overridden, and that stages are gradual rather than sudden.

Modern authors have argued for a connection between the harshness of toilet training during the second year and conformity during adulthood, or between multiple caretakers during infancy and a fragile emotional security in adolescence.

Freudian theory depends upon the assumption that the emotional environment of the child’s first five years has a persistent effect upon his development, which can only partially be modified by later events. Modern students of cerebral function partially support such a view by assuming that psychological experience involves changes in brain cells and their connections with each other. but is this assumption of gradualism and continuity really justified?

Kagan points out that “the development of the embryo contains frequent discontinuities in which some structures disappear after their mission has been accomplished, leaving no structural residue.” evidence is lacking that even severe emotional disturbance in early childhood necessarily has permanent effects upon adult adjustment. One study of European children who were adopted by American families because they had been left homeless by the Second World war showed that about 20 percent showed severe signs of anxiety. “But, over the years, all of these symptoms vanished; the vast majority of the children made good school progress; and there was no case of academic difficulty among them.” Nor were there any persistent emotional difficulties in relation to their adoptive families.

it is encouraging to realize that even children who exhibit psychological symptoms serious enough to require treatment at a child-guidance clinic are not especially likely to show disturbances in adult life. Even the temperamental differences between infants along the dimension of “inhibition” can become substantially modified in later childhood. What emerges most forcefully from the evidence adduced by Kagan is that until now psychologists and psychiatrists have given too much weight to the power of later events to mold and alter the individual.

Parents who hope that a book with this title will provide a blueprint for child-rearing will be disappointed. Kagan is neither a Spock nor a Freud. On the other hand, those who really want to know what modern research into infant and child development has to say will be amply rewarded. Kagan is a skeptical, conscientious scientist who is reluctant to go beyond the facts, and who constantly questions received opinion, with illuminating result.

the nature of the child