1340 



HORMONAL REGULATION OF BEHAVIOR 



may set the stage for its behavior at a later 

 stage, so that the behavior at the later stage 

 may appear quite normal, even though it 

 is the animal's first experience, and even 

 though learning did play a role in the de- 

 velopment of the animal's capability for 

 jierforming this behavior. If, by hormone 

 treatment, we can put the animal directly 

 into the physiologic condition characteristic 

 of a later stage in the cycle, and then con- 

 front it with the situation characteristic of 

 that stage, when it has not had any experi- 

 ence of the earlier stage, it is sometimes 

 possible to throw into startling relief the 

 role of experience in the progression of 

 stages which normally occurs effectively 

 even in the first breeding episode. 



Rosenblatt and Aronson (1958a, b) have 

 shown that previous sexual experience is an 

 important variable affecting the induction 

 of sexual behavior by androgen administra- 

 tion in male cats, and Valenstein, Riss and 

 Young (1955) and Valenstein and Young 

 (1955) found somewhat similar results in the 

 guinea pig. The importance of considering 

 species differences in such matters is seen 

 in the fact that such previous experience 

 appears to be unimportant in rats, compared 

 to the other animals mentioned (Kagan 

 and Beach, 1953; Beach, 1958b I. These 

 studies are reported more fully in the 

 chapter by Young. 



Lehrman (1955) found that ring doves 

 with previous breeding experience could be 

 induced to feed young doves (by regurgita- 

 tion) by the injection of approximately 450 

 I.U. prolactin over 7 days. Similar treat- 

 ment of birds of the same age, but without 

 previous breeding experience, failed to in- 

 duce parental feeding behavior. Inexperi- 

 enced birds so treated showed a striking 

 suppression of sexual behavior, compared 

 with untreated birds, and gave several be- 

 havioral signs of tension that are normally 

 seen in animals before they regurgitate. 

 However, they failed to make the ap- 

 proaches to the young which were reliably 

 induced in experienced birds. The experi- 

 enced birds did a great deal of gentle 

 pecking at the head and body of the stimu- 

 lus squabs, mostly concentrated on the 

 head (the squabs normally respond to gentle 

 pecking on the head by making the "beg- 



ging" movements which elicit regurgita- 

 tion feeding). The inexperienced birds, on 

 the other hand, did very little pecking of 

 the young (no more than they did at other 

 objects in the cage) , and what pecking they 

 did was not in any way directed at or 

 concentrated on the head of the squabs. It 

 was apparent that the prolactin injection 

 had induced in both these groups of birds 

 a condition of tension, probably associated 

 with the engorgement of the crop by the 

 cropmilk produced in response to prolactin 

 treatment, but that the inexperienced birds 

 could not respond differentially to that part 

 of the environment (the squabs) which 

 could potentially provide stimulation which 

 would reduce this tension. 



Lehrman and Wortis (1960) used the 

 same method in dealing with incubation be- 

 havior induced by progesterone injection. 

 It will be recalled that experienced ring- 

 doves can reliably be induced by progester- 

 one administration to sit on eggs. We have 

 compared the reaction of ring doves with 

 and without previous experience to eggs 

 presented by the experimenter, after the 

 birds were injected with 100 /xg. per day of 

 progesterone for 7 days before being tested. 

 Striking differences were found between 

 the behavior of the experienced and of the 

 inexperienced birds. The experienced birds 

 are all recorded as standing near the nest in 

 less than one minute after being introduced 

 into the test cage, whereas the median la- 

 tency for this behavior in the inexperienced 

 birds was 35 minutes. All of the experienced 

 birds settled on the eggs for the first time 

 within 26 minutes, whereas no inexperienced 

 bird sat on the eggs in less than 56 minutes, 

 and half of them did not sit at all. Birds riot 

 injected with progesterone pay no attention 

 to the eggs on the first day after being 

 placed in the test cage, regardless of whether 

 they are experienced or not. 



It is clear that the animal's previous ex- 

 perience can alter the ways in which its be- 

 havior is influenced by hormone treatment, 

 and that the interaction between the effects 

 of previous experience and of hormone 

 treatment is capable of providing a fruit- 

 ful approach to the analysis of the develop- 

 ment of the behavior patterns and of their 

 physiologic bases. 



