Following a 50-day period of cohabitation with females, 36 male rats were tested in their home cages for sexual vigor and for preference for odors from normal receptive vs. nbiireceptive females. 2 mo. prior to odor preference testing, 13 sexually active and 6 inactive Ss were castrated; 12 active and 5 inactive Ss served as controls. Active normal Ss preferred receptive-female ; odor over nonreceptive-female odor (p < .01), but inactive normal Ss and castrates showed no preference for either feminine odor. Active normal Ss spent more time than did other Ss investigating nonreceptive-female odor as well as receptive-female odor (p < .05).

Among normal or castrated male rats, 56 sex-experienced and 60 naive rats showed no preference for normal vs. castrated male odors. In a second study, 24 naive receptive females preferred nonreceptive over receptive female odors (p < .05), but 25 naive nonreceptive and 42 experienced females showed no preference. In a third study, 50 immature males injected with testosterone preferred receptive over nonreceptive female odors (p < .01), but 40 placebo-injected rats showed no preference. Thirty immature males preferred normal over castrated male odors (p < .05). In a fourth study, 23 segregated-receptive immature females preferred normal over castrated male odors (p < .01), but 20 segregated-nonreceptive and 27 cohabiting females showed no preference. Twenty-one segregated-receptive immature females preferred nonreceptive over receptive female odors (p < .05), but 31 segregated-nonreceptive and 40 cohabiting females showed no preference.

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