[332 



HORMONAL REGULATION OF BEHAVIOR 



IV. General Discussion: the Psychobiol- 



ogy of Parental Behavior and 



the Role of Hormones 



A. LEARNING AND HORMONE-INDUCED 

 PARENTAL BEHAVIOR 



1. General: FoDiiulation of the Problems 



We have presented a great deal of evi- 

 dence that the patterns of parental behavior 

 vary in characteristic ways from species to 

 species, and are relatively constant within 

 species. Obviously, then, genetic differences 

 between the species must play a consider- 

 able role in the establishment of these dif- 

 ferences. Discussions of the role of learning 

 in the development of such behavior pat- 

 terns are often the occasion for vigorous 

 controversy because various investigators 

 differ with respect to the relative heuristic 

 value which they assign to the formal iden- 

 tification of characters as being "innate" 

 (or "inherited") or "learned" (or "ac- 

 quired"), and with respect to their method 

 of approach to the study of ontogeny, to 

 the terminology they use to identify the 

 effects of environment and the effects of 

 genetic differences, to the type of behavior 

 which interests them, etc. We cannot go into 

 details of this "nature-nurture" problem 

 here, except for the purpose of bringing into 

 perspective our discussion of the role of 

 learning in the development of parental be- 

 havior patterns (for discussion of these 

 problems see Lorenz, 1937; Tinbergen, 1951 ; 

 Lehrman, 1953, 1956b; Hebb, 1953; Ken- 

 nedy, 1954; Koehler, 1954; Schneirla, 1956; 

 Eibi-Eibesfeldt and Kramer, 19581. 



A first stage in the study of the effect of 

 experience on any behavior pattern is to 

 determine whether and in what ways the 

 pattern can develop w4ien the environment 

 is restricted in various ways, so that par- 

 ticular kinds of experience are not available 

 to the animal. Such experiments may illu- 

 minate the contribution of various kinds of 

 environmental experience to the develop- 

 ment of the behavior. Furthermore, when 

 we find that particular kinds of experience 

 do 7tot contribute to the development of the 

 behavior pattern, we have also learned 

 something significant about the behavior 

 (Tinbergen, 1955). However, since the cen- 

 tral problem is that of the development of 



the behavior, experiments of this type do 

 not give a final answer to the question of 

 what has contributed to the formation of 

 the behavior (Schneirla, 1956). We do not 

 by any means know all the possible va- 

 rieties of learning processes (Maier and 

 Schneirla, 1942) , and this limits our ability 

 to perceive the most significant relation- 

 ships during development. Furthermore, we 

 are just beginning to appreciate the variety 

 and subtlety of the ways in which very 

 early experience contributes to the develop- 

 ment of adult behavioral capacities in va- 

 rious kinds of animals (Hebb, 1949, 1953; 

 Beach and Jaynes, 1954) . 



This means that the question of whether 

 any particular kind of learning has or has 

 not contributed to the development of a 

 behavior pattern is only one step in the 

 analysis of its ontogeny. Unfortunately, for 

 the great majority of behavior patterns, this 

 is the only step that has yet been taken. 



In dealing with the problem of the con- 

 tribution of learning to the development of 

 patterns of parental behavior, therefore, we 

 are simply analyzing, to the extent that the 

 available data permit, one of the influences 

 on the ontogeny of the behavior. It should 

 not be thought that we are seeking answers 

 to, or even formulating, "final" questions 

 about the nature of environmental influ- 

 ences. Later parts of this discussion will in- 

 dicate some of the ways in which exjieri- 

 ential influences may be related to various 

 kinds of organic factors during develop- 

 ment. 



2. Learning and Parental Behavior 



Behavior of inexperienced and of expe- 

 rienced MOTHERS, (a) Comparison of primip- 

 ara and multipara. Chimpanzee mothers who 

 have previously borne young appear to be 

 much more efficient and skillful in caring for 

 their infants than are primiparous animals 

 (Yerkes, 1935; Yerkes and Tomilin, 1935; 

 Yerkes and Elder, 1937; Nissen and Yerkes, 

 1943). Primiparous chimpanzees, when first 

 confronted with their own young, usually 

 appear indifferent to or fearful of the new- 

 born, and handle them clumsily, or not at 

 all. Such an animal is likely to act "sur- 

 prised, puzzled, baffled, and at a loss as to 

 what to do," and may do such things as 

 holding the infant head down, biting its 



