Testing began at 90 days of age. Effects of rearing on homosexual behavior Testing took place during the dark phase of the light cycIe, under dim in tbe male laboratory · illumination from a 25 W red light bulb. In each of 10 days, a stimulus male (interloper) of the same age was JOHN A. ALLEN and ROBERT BOICE introduced into the home cage of each University of Missouri, Columbia, Mo. 65201 resident rat for 15 min. The three stimulus males were marked on their Thirty-six male laboratory were raised in one of three conditions: social flanks and backs. They were presented isolation, sexual segregation, Ol cohabitation with females. Male int~rlopers in rotating· order to prevent two introduced into th~ individual cages of adults elicited the most mountmg and consecutive uses of the same animaI. thrusting in isolates. Analysis of concomitant social behaviors suggests that the The order in which residents were mounting functioned as a component of dominance processes; offensive postures tested was randomized daily. and mounts correlated significantly in the group raised as isolates. Frequency measures were recorded for a variety of social acts and postures Segregation of the sexes may be a problem is that homosexuality must exhibited by residents: ano-genital prime factor in the etiology of animal often be inferred from poor sniffs, aggressive grooms, displacement homosexuality. Avery (1925) and performance in heterosexual grooms, offensive postures (sideways Loutitt (1927) found homosexual cQPulation. Even where homosexual and upright), elevated crouches, and mounts common in male guinea pigs activity has been observed (Beach, mounts (after Grant & Mackintosh, caged together. Segregated male 1942b), details are omitted. 1963). laboratory rats were reported to In general, homosexual behaviors RESULTS "attempt a complete copulatory act" remain ignored and iII-defined, even . The percentages of Ss that mounted prior to heterosexual intercourse though they are " ... known to occur an interloper at least onee during the (Stone, 1922,p. 123). Mounting of in practlcally every species of mammal 10 tests were 50, 16.6, and 8.3 for the male interlopers occurs after which has been extensively studied isolation (I), segregation (S), and segregated raising (Grant, 1963) and in [Kinsey, Pomeroy, Martin, & Gebhard, cohabitation (C) conditions, groups of male wild rats (Barnett, 1953, p. 448]." MaIe homosexuaIity respectively. Group differences in 1958). in the absence of "appropriate" sexual mounting of stimulus animals were Jenkins (1928) hypothesized that objeets is reported only briefly in statistieally reliable (Table 1). male rats segregated at an early age swine (Hafez, Sumption, & Jakway, Significant differences between came to prefera homosexual stimulus. 1962), dogs (Fuller & Dubois, 1962), groups were also found in frequency She found that segregation be fore rabbits (Brown, 1937), and rhesus of ano-genital sniffing (C males highest puberty did produce more approaches monkeys (Kempf, 1917). and I males lowest) - and defensive over an electrified grid to males than The purpose of the present study postures (C> I> S). Group to estrous f.emales. Beach (1942a) was to compare effects of three rearing differences were not reliable for found that males segregated at 21 days conditions, isolation, sexual aggressive _grooms, displacement of age performed poorly in segregation, and cohabitation with gr ooms, offensive postures, and heterosexual tests of copulation females, on subsequent social and elevated crouches (Table 1)_ compared to rats raised in isolation or sexual behaviors toward interlopers. Table 2 is an analysis of mounts by in cohabitation with females. Emphasis was directed at relationships days. There was no systematic increase Interestingly, rats segregated with between homosexual behaviors and or decrease in mounts over the 10 days females were only intermediate to other social/agonistic behaviors. of testing. isolates. SUBJECTS Spearman rank correlation In general, however, the literature is The Ss were .36 male offspring coefficients were computed between con tradictory about this point. selected from litters o( nine aH possible pairs of behavioral Folman & Drori (1965) corroborated Sprague-Dawley mothers measures in Group 1 (Table 3). Beach's findings only in part and "time-mated" by the suppHer. Those Significant correlations were obtained obtained contradictory results in two raised in group conditions were housed between mounts and offensive comparable studieS: Gerall, Ward, & in Wahmann suspended cages, postures and between elevated Gerall (1967) founa- no significan~ 40 x 12 x 12 cm, with mesh floors and crouches and displacement grooms. difference between copulatory ability fronts. Isolates were housed in DISCUSSION of male rats raised in segregation or individual Wahmann cages, This study suggests a significant cohabitation. 20 x 24 x 18 cm. All had free access to influence of early social isolation on Even though Beach (1942a) found Lab Blox and water. A reversed 12-h adult homosexual behavior. Males isolated males to be better copulators light cycle was maintained in the raised in isolation mounted interloping than those raised socially, there is eolony throughout. males more often than did males raised reason to expect isolation to have the PROCEDURE in sexual segregation or eohabitation opposite effect. For example, Drori & At 21 days of age, 36 males were with females. Within Group 1, the Folman (1967) and Gerall, Ward, & weaned and assigned by split-litter typical pattern of the homosexual Gerall (196-7) found iso la ted males to technique to one of three rearing behavior sequence is reflected in the be significa:1tly inferior copulators conditions: social isolation, positive correlation between offensive compared to socially raised males. One monosexual segregation, or postures and mounts. - cohabitation with females. Each of 12 A typical behavior pattern of *Based on a thesis submitted by the first males in the cohabitation condition author to the Graduate School, University homosexual. mounting was evident. In of Missouri, in partial fulfillment of shared a cage with three females of the those encounters involving more than requirements tor the MA degree, 1970. Tbe same age. Segregated males were one mount, eaeh mount was authors thank Dr. D. C. Wright for his housed in three cages, each containing commonly preeeded by tnis sequence: helpful advice. Send reprint requests to R. Boice, Department of . 209 four Ss. Initial mounts oceurred between 2 and McAlester Hall, University of Missouri, At 85 days of age, an Ss were 12m i n (mode = 5 min) after Columbia. Mo. 65201. transferred to clean individual cages. introduction of the interloper. The

Psychon. Sei., 1971, Vol. 23 (5) 321 Table 1 guinea pigs. Journal of Comparative Sociosexual Behavior in Groups of Rats Raised in Isolation (I), Sexual Segregation (S), Psychology, 1925,5,373-396. BARNETT, S. A. An analysis of social or Cohabitation With Ff'males (C) Over All 10 Days. One-way analysis of variance was behavior in wild rats. Proceedings of the used to test significance (F) between grau ps. Zoological Society of London, 1958, 130,107-152. Mean Group F BARNETT, S. A., & STODDART, R. C. Effects of breeding in captivity on S C (df = 2,33) conflict among wild rats. Journal of Mammalogy, 1969,50,321-325. Ano-Genital Sniffs 56.0 70.6 73.9 3.49* BEACH, F. A. Comparison of copulatory Aggressive Grooms 19.8 26.7 32.3 2.06 behavior of male rats raised in isolation, Displacement Grooms 22.0 20.8 20.5 < 1 cohabitation, and segregation. Journal of Offensive Postures 4.6 7.3 4.8 < 1 Genetic Psychology, 1942a, 60,121-136. 11.0 3.59* BEACH, F. A. Analysis of the stimuli Defensive Postures 9.5 5.2 adequate to elicit mating behavior in the Elevated Crouches 3.0 5.5 6.5 2.03 sexually inexperienced male rat. Journal Mounts 8.5 1.3 1.8 2.70* of , 1942b, 33, 163-207. *p < .05 BROWN, R. H. Stability of conditioning and sexual dominance in the rabbit. Table 2 Science, 1937, 86, 520. Mounts by Days for Rearing Condition Groups CALHOUN, J. B. A "behavioral sink." In E. L. Bliss (Ed.)" Roots of behavior. New Test Days York: Harper, 1962. Pp. 295-315. DRORI, D., & FOLMAN, Y. The sexual 1 2 3 4 5 6 7 8 9 10 behavior of males unmated to sixteen months. of age. Animal Behaviour, 1967, Mean .91 .83 .66 .41 .75 1.10 .58 1.08 .33 . 50 15,20-24. Isolation 1.36 1.41 1.11 1.70 .84 .95 FOLMAN, Y., & DRORI, D. Normal and SD 1.70 1.67 1.10 .75 abberant copulatory behavior in male rats .16 .08 .16 .25 .25 .08 . 08 (R. norvegicus) reared in isolation . Segregation Mean SD .36 .26 .54 .59 .82 .26 . 26 Animal Behaviour, 1965, 13, 427-429 . FULLER, J. L., & DUBOIS, E. M. The .33 .33 .25 behavior of dogs. In E. S. E. Hafez (Ed.), Cohabitation Mean .41 .16 SD 1.37 .54 1.10 1.10 . 82 The behavior of domestic animals. Baltimore: Williams & Wilkins, 1962. Pp. 415-452. Table 3 GERALL, H. D., WARD, 1., & GERALL, A. Intercorrelations' 'Amona: Sociosexual Behaviors of Rats .Raised in Isolation (N = 12) Disruption of the male rat's sexual behavior induced by social isolation. (b) (c) (d) (e) (f) (g) Animal Behaviour, 1967, 15, 54-58. GRANT, E. C. An analysis of thy social Ano-Genital Sniffs (a) .15 .36 -.14 .38 .36 . 19 behavior of the male laboratory rat . Aggressive Grooms (b) .05 .37 -.08 .09 .07 Behaviour, 1963, 21, 260-281. GRANT, E. C., & MACKINTOSH, J. H. A Displacement Grooms (c) .07 -.07 .62* .02 comparison of the social postures of some Offensive Postures (d) .32 -.05 .64* common laboratory rodents. Behaviour, Defensive Postures (e) .03 .33 1963, 21, 246-259, Elevated Crouches (f) .06 HAFEZ, E. S. E., SUMPTION, L. J., & Mounts (g) JAKWAY, J. S. The behavior of swine. In E. S. E. Hafez (Ed.), The behavior of *p < .05 domestic animals. Baltimore: Williams & Wilkins, 1962. Pp. 334-369. resident always initiated the behavioral stressful situation, where elicited JENKINS, M. The effect of segregation on sequence. Repeated instances of the sexual behavior of the white rat as inhibited an adaptive measured bY the obstruction method. aggressive grooming of the interloper avoidance response. The a:ppearance of Genetic Psychology Monographs, 1928, were interspersed with offensive homosexual mounting in the elicited 3,457-471. posturing by the resident. Successive aggression eontext also suggests a role KEMPF, E. J. The social and sexual behavior of the infra human primates attacks culminated in mounting, with for soeial dominance; a dominant male with some comparable facts in human thrusts and palpitations, often felling rat shows sexual responses during an behavior. Psychoanalytic Review, 1917, the interloper. The interloper eneounter with a subordinate male rat 4, 127-154. KINSEY, A. C., POMEROY, W. B., reacted with squeals and attempts at (Reynierse, in press). In the present MARTIN, C. E., & GEBHARD, O. O. flight. Posteopulatory grooming was study, offensive postures and mounts Sexual behavior in the human female. not eonsistently present, although it were significantly correlated in Philadelphia: Saunders, 1953. occurs reliably following heterosexual Group 1. An interloper with its LOGAN, F. A., & BOICE, R. Aggressive behavior of paired rodents in an mounts (Grant & Mackintosh, 1963). tendency to be submissive is avoidance context. Behaviour, 1969, 34, Perhaps the explanation of effects a p par e n tly a good releaser for 161-183. of social isolation should foeus on mounting when the males are at least LOUTITT, C. M. Reproductive behavior of the guinea pig. I. The normal mating isolation as a stressor. Stress, as a somewhat domesticated (Barnett & behavior. Journal of Comparative factor in producing homosexuality, Stoddart, 1969). Interlopers in the Psychology, 1927, 7, 247-263. has been suggested elsewhere. Calhoun present study displayed only REYNIERSE, J. H. Submissive postures (1962) reported widespread submissive postures. during shock-elicited aggression. Animal Behaviour, in press. homosexuality in an overcrowded STONE, C. P. The congenital sexual "behavioral sink. " Logan & Boice behavior of the young male albino rat. (1969) found homosexual mou'nting REFERENCES Journal of Comparative Psychology, following shoek termination in a AVERY, G. T. Notes on reproduction in 1922, 2, 95-153.

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