HORMONES AND MATING BEHAVIOR 



1219 



the two social situations might be explained 

 by the earlier maturation of animals in this 

 stock. He suggested that if males were 

 weaned and isolated at 10 days of age in- 

 stead of on day 25, a greater difference might 

 be shown between the isolated animals and 

 those brought up in the social situation. In 

 the first test a completely convincing confir- 

 mation of the hypothesis was given (Table 

 19.3, group IV). The failure to obtain a 

 greater difference in the earlier experiment 

 with the heterogeneous males (group I) was 

 obviously attributable to the circumstance 

 that the contact these animals had with 

 other animals during the first 25 days was 

 sufficient to insure the development of essen- 

 tially normal patterns of sexual behavior. 



The possibility that an adult male with- 

 out previous opportunity for organization 

 of the higher measures of sexual behavior 

 could improve his sexual performance by 

 contact with other animals at an older age 

 has been investigated (Valenstein and Goy, 

 1957) . Each of several genetically heteroge- 

 neous males which had not exhibited any of 

 the more mature behavior in tests given dur- 

 ing the period of isolation was placed with 2 

 females for 23 days when they were 320 to 

 430 days of age. In subsequent tests all these 

 males demonstrated the ability to mount, to 

 have intromissions, and to ejaculate. Strain 

 2 males at older ages did not acquire 

 the copulatory pattern so readily; 2 of 5 

 achieved intromission and ejaculation after 

 being placed with females, Ibut none of the 

 remaining 3 displayed any of the higher 

 measures of sexual behavior. The result 

 is consistent with the earlier finding (Valen- 

 stein, Riss and Young, 1955) that young 

 males from this strain require a longer 

 time to organize this pattern of behavior. 

 The data as a whole indicate that the emer- 

 gence of sexual behavior patterns in the 

 male guinea pig is not restricted to an 

 early critical period comparable with that 

 described in the literature dealing with im- 

 printing (Lorenz, 1937). On the other hand, 

 an analysis of the data i)resented by Valen- 

 stein and Goy (1957) reveals that contact 

 with other animals is not as effective in or- 

 ganizing tissues for mating in older males 

 as it is in young males. 



What was regarded as a crucial test of 

 the effect of the experiential factor on the 



character of the soma w^as a comparison 

 of the response of isolated and socially 

 reared strain 2 males to androgenic stimula- 

 tion (Valenstein and Young, 1955). Follow- 

 ing 7 tests which revealed the difference in 

 their performance, the males brought up 

 under the two social conditions were cas- 

 trated, allowed to go without treatment 

 until the regression in sexual behavior had 

 reached the base-line of change, and then 

 injected daily with testosterone propionate 

 until the precastrational level of behavior 

 was reached. The return of each group to 

 the level characterizing it before castra- 

 tion is evidence for the conclusion that the 

 responsiveness of the tissues mediating mat- 

 ing behavior to androgenic stimulation had 

 been altered by a psychologic factor. 



The results from the studies on the male 

 guinea pig are felt to have provided a 

 sound basis for a hypothesis that would 

 account for the establishment of patterns of 

 sexual behavior in this species. They sug- 

 gest that the nervous organization on which 

 response to sexual stimulation depends is 

 influenced at a very early age by contact 

 with other animals. On the other hand, 

 genetical as well as experiential factors are 

 important and the pattern displayed in re- 

 sponse to androgenic stimulation is a re- 

 sultant of the co-action of the two factors. 

 But indirectly the testicular hormone may 

 also be involved in the establishment of 

 these patterns of behavior. To be sure, their 

 organization, as estimated by mounting pro- 

 ficiency, can occur in the absence of the 

 testes (Beach and Holz, 1946; Riss, Valen- 

 stein, Sinks and Young, 1955). On the other 

 hand, if the organization of these pat- 

 terns depends on experience gained through 

 mounting, the testis hormone, by increasing 

 this activity, may exert an indirect influence 

 on the neural tissues in which the organiza- 

 tion of patterns occurs. 



Before leaving the male, we would call 

 attention to the hypothesis that in the rat 

 and guinea pig the copulatory response is 

 innate rather than acquired (Stone, 1922; 

 Louttit, 1929; Beach, 1942g, 19421, 1951; 

 Kagan and Beach, 1953) . The data reviewed 

 for the guinea pig j^rompted us to question 

 the validity of the hypothesis for this spe- 

 cies. The report that palpation with pelvic 

 thrusts occurs in the rat as early as day 



