1220 



HORMONAL REGULATION 



21 (Beach, 1942c » suggested that such con- 

 tact with siblings might be sufficient to 

 organize the adult pattern of sexual be- 

 havior in this species (Valenstein, Riss, 

 and Young, 1955). Beach (1958a) believes, 

 however, from the results of a more recent 

 experiment, that this possibility can be ex- 

 cluded. 



Males were isolated at 14 days just when 

 the eyes are opening and before they could 

 possibly have had experience mounting 

 their cage-mates. At age 90 to 100 days 

 13 experimental animals and 12 siblings 

 which had been reared together were tested. 

 In the first 10-minute test, 4 of the experi- 

 mental and 5 of the control males mated. 

 The copulatory performance of the experi- 

 mental animals was perfect. Without ex- 

 ception the first mount resulted in intro- 

 mission. The latencies (seconds from the 

 time the female is placed in the cage to the 

 first intromission) were 195, 180, 60, and 

 8 seconds. In the controls the latencies were 

 110, 105, 75, 40, and 25 seconds. The aver- 

 age number of intromissions before ejacu- 

 lation was 8.2 for the experimental males 

 and 7.0 for the controls. Zimbardo (1958» 

 was frankly critical of this latter experiment 

 and, as we have noted, states that his re- 

 sults are in agreement with those obtained 

 from the guinea pig. If he is correct, the 

 rat is not a species in which development of 

 the copulatory response l)y the male is 

 innate; on the contrary, it should l)e placed 

 with the guinea pig, cat, and chimpanzee 

 in which some influence of contact with 

 other animals contributes to the patterning 

 of sexual behavior. 



Regardless of the status of the rat/" foi' 



^"The reader who has reached this point will 

 be keenly aware of the extent to which data from 

 the rat and guinea pig have contributed to the 

 thinking of investigators interested in the hor- 

 mones and mating behavior. He will also recall 

 that there are many references to similarities and 

 differences between these species. For his con- 

 venience, they are listed here. 



Differences between the species would appear to 

 be more numerous than similarities. The hormones 

 which elicit male and female behavior are the same 

 (Dempsey, Hertz and Young, 1936; Boling and 

 Blandau, 1939; Beach, 1942a; Stone, 1939a; Beach 

 and Holz-Tucker, 1949) and in both species it is 

 clear that differences between individuals have a 

 somatic rather than a hormonal basis (Young, 



no investigator has denied that there is 

 some influence of contact with other ani- 

 mals, the conclusion is clear that in all 

 species studied the character of sexual be- 

 havior is influenced l)y an experiential 

 factor. Of importance for one who would 

 generalize, is the fact that most studies 

 were of male ; only in Nissen's work on the 

 chimpanzee were data obtained from the 

 female. As a means of narrowing this gap, 

 a study of the female guinea pig was under- 

 taken (Goy and Young, 1957a). The re- 

 sults, although leaving much to be ex- 

 plained, are striking. In the strains which 

 display mounting behavior the amount dis- 

 l)layed by females reared in isolation was 

 consistently less than that displayed by fe- 

 males raised with other animals. In all 

 strains the duration of heat was shorter in 

 the isolated females, as was the duration 

 of lordosis. The effect on mounting behavior 

 was not imexpected, especially if this meas- 

 ure of estrous behavior is a homologue of 

 the behavior displayed by the male (Beach, 

 1943 ». At the moment, however, we cannot 

 account for the shorter duration of heat and 

 maximal lordosis in the isolated females. 

 These measures are generally thought to be 

 reflex in nature and therefore independent 

 of any influence from other animals. 



A final suggestion with respect to ex- 



Dempsey, Myers and Hagquist, 1938; Beach and 

 Holz-Tucker, 1949 ; Grunt and Young, 1952b ; Val- 

 enstein and Young, 1955; Goy and Young, 1957b). 

 The basic pattern of behavior in females of the two 

 species is similar (Ball, 1937b; Young, Dempsey and 

 Myers, 1935; Blandau, Boling and Young, 1941), 

 but the patterns of beha\ior characteristic of the 

 males are different (Stone, 1922, 1924b; Stone, 

 Tomilin and Barker, 1935; Stone and Ferguson, 

 1940; Beach, 1944b; Beach and Holz, 1946; Young 

 and Grunt, 1951). In the male rat the strength of 

 sexual behavior is considered proportional to the 

 amount of exogenous testicular hormone (Beach 

 and Holz-Tucker, 1949; Beach, 1956); data from 

 the male and female guinea pig do not support 

 such a conclusion (Grunt and Yoimg, 1952b; Riss 

 and Young, 1954; Goy and Young, 1957b). Male- 

 like mounting by the female rat does not coincide 

 closely with estrus and appears to be displayed 

 independently of the ovarian hormones (Beach 

 and Rasquin, 1942) ; in the female guinea pig 

 mounting is displayed only during the proestrum 

 and estrus, or in spayed animals only following 

 treatment with estrogen and progesterone (Young. 

 Dempsey, Hagquist and Boling, 1939; Young and 

 Rundlett, 1939; Goy and Young, 1957a, b). 



