HORMONES AND MATING BEHAVIOR 



121' 



puberty the animals were paired under ob- 

 servation in male-female combinations, and 

 in such a way that the younger inexperienced 

 animal was with an older experienced animal 

 of the opposite sex. In many hundreds of ses- 

 sions the complete pattern did not occur, al- 

 though almost all the component or unit 

 acts composing the pattern did appear. In 

 Nissen's words, except for minor modifica- 

 tions, the component acts are either innate 

 or learned in early life without the act of 

 learning being observed. The complete se- 

 quential pattern of mating behavior, on the 

 other hand, is not innately determined, or 

 at best, the innate factor is only a readiness 

 or predisposition to learn. 



The establishment of the biologically ef- 

 fective pattern of mating behavior, in which 

 there is a precise temporal organization of 

 the components and in which the response 

 of each animal is adjusted to that of the 

 other, seems to be a matter of trial-and-error 

 learning, which can be viewed in terms of the 

 statistical probability that certain concate- 

 nations of behavior on the part of the two 

 animals will occur. Several factors can be 

 identified as increasing or decreasing such 

 a probability. First and foremost is the ac- 

 tivity level, the more and the more varied 

 the activity, the more likely is the occurrence 

 of the critical pattern. Closely related with 

 this first factor is that of age. As the chim- 

 panzee matures, he slows up in the amount of 

 activity in which he engages. As he slows up, 

 the probabilities of there being the concate- 

 nation mentioned above are reduced. 



The guinea pig probably has been studied 

 more completely than any other species. 

 Preliminary experiments yielded data bear- 

 ing on the performance of segregated versus 

 isolated males, the influence of frequent cop- 

 ulatory experience, the strength of sexual 

 behavior of dominant and submissive males, 

 and the effect of confinement of adult males 

 with females. 



When relatively young and sexually inex- 

 perienced males were tested (Young, Grunt 

 and Valenstein, 1951), experience gained 

 during 10 tests did not reveal any difference 

 between the performance of 37 males raised 

 with other males and that of 32 isolated 

 males which could not be accounted for by 

 adaptation to the presence of another animal 

 at the time of the tests. 



In an exi)eriment in which freciucnt sexual 

 experience was given (Riss, unpublished 

 data ) , 4 males having average scores of 11.2, 

 8.4, 6.6, and 5.5 in 10 perliminary tests were 

 tested daily for 51 days. Improvement was 

 shown by the male whose score was 6.6. He 

 became the most active copulator in the 

 group with an average score of 9.2 for the 

 last 20 of the 51 daily tests, but he was the 

 only male whose behavior clianged. 



A comparison of these results obtained on 

 the guinea pig with those obtained by Lars- 

 son (1959) on the rat would be of interest, 

 but different data were recorded so a com- 

 l)arison cannot be made. Larsson found, 

 however, that learning intervened only in 

 determining the lengths of the postejacula- 

 tory latencies; the other changes appearing 

 in the pattern of behavior with increasing 

 age were consequences of maturing proc- 

 esses. 



In a study of dominance and submissive- 

 ness (Riss, unpublished data) the behavior 

 of 16 male guinea pigs that had received 10 

 lireliminary tests deviated markedly in a 

 competitive situation, according to the dom- 

 inance or submissiveness of the animal, but 

 when they were replaced in isolation the be- 

 havior returned to a level not greatly differ- 

 ent from that shown during the preliminary 

 tests. Clearly this experience had little or no 

 lasting influence on the pattern of behavior 

 characterizing the individuals. 



Sexual performance was affected signifi- 

 cantly in these experiments only after a 

 number of low score males had been con- 

 fined with adult females for 60 days (Riss 

 and Young, 1953). Before their confinement 

 with the females the average score achieved 

 by 7 males in 10 tests was 3.8 whereas after 

 confinement and return to isolation the aver- 

 age score in 10 tests was 4.9. The difference is 

 significant at the 5 per cent level. A group of 

 7 males never removed from isolation had 

 average scores of 4.5 and 4.7. 



If any impression came out of these pre- 

 liminary experiments, it was one of fixation 

 or stability of the individual pattern of sex- 

 ual behavior. Not until experiments were 

 performed in which very young animals were 

 used, was there any clear indication of the 

 extent to which contact with other animals 

 affects ]iatterns of behavior in the male 

 guinea pig (Valenstein, Riss and Youne, 



