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WILLIAM C. YOUNG
conclusion would be consistent with the opinions expressed by those
who have looked into the corresponding problem in the lower vertebrates, and which are summarized in the earlier parts of this chapter.
Other types of behavior in mammals which at one time or another
have been associated with gonadal hormone activity are aggressiveness,
nest building, and parental behavior. Aggressiveness has been studied
in several of the rodents, a group of rhesus monkeys, and the chimpanzee. Only in the rhesus monkey was the administration of gonadal
hormones without effect on the hierarchy or dominance relations (349).
This may perhaps be accounted for, Mir sky states, by the unusually
violent aggressiveness which characterizes this species. In the case of
the other species, the results from the many well-controlled experiments
were uniform in revealing the influence of androgens and estrogens—
depending on the situation—on the display of aggressive or dominance
behavior. At the time of maximal genital swelling or following treatment
of ovariectomized individuals with estradiol benzoate, female chimpanzees were dominant in competitive trials for a food reward (350-353
and several older reports from the Yerkes Laboratory of Primate Biology). A castrated male receiving the same estrogen became subordinate,
but when he was given methyl testosterone at a time when he was the
dominant member of a pair, his dominance became enhanced (350).
After similar treatment a subordinate female obtained most of the food.
The aggressiveness of male rats and mice largely disappeared following
castration (354—358) and it was increased or restored by injections of
testosterone propionate (355-357, 359, 360). The manner of action of
androgens and estrogens in producing these varied effects is not known.
The problem is complicated by the sudden remission of aggressive behavior at the time of estrus in female guinea pigs, hamsters, short-tailed
shrews, and probably many other mammals (78-80) when estrogen levels
are thought to be at their highest. The observation by Kislak and Beach
(80) that the administration of progesterone to an estrogen-conditioned
and aggressive female hamster is followed immediately by a loss of the
aggressiveness is an important lead, but its relevance for the broader
problem is not now apparent.
The relationship of the hormones to nest building and parental behavior has been reviewed (7). The subject is complex, many of the
results are contradictory, and no more than tentative conclusions are
justified. Two points made early in the review are important and will
be repeated here. The temporal relationships between ovulation, on the
one hand, and mating, nest building, and parental behavior, on the other,
are different in birds and mammals. In birds nest building, mating, and
WILLIAM C. YOUNG
conclusion would be consistent with the opinions expressed by those
who have looked into the corresponding problem in the lower vertebrates, and which are summarized in the earlier parts of this chapter.
Other types of behavior in mammals which at one time or another
have been associated with gonadal hormone activity are aggressiveness,
nest building, and parental behavior. Aggressiveness has been studied
in several of the rodents, a group of rhesus monkeys, and the chimpanzee. Only in the rhesus monkey was the administration of gonadal
hormones without effect on the hierarchy or dominance relations (349).
This may perhaps be accounted for, Mir sky states, by the unusually
violent aggressiveness which characterizes this species. In the case of
the other species, the results from the many well-controlled experiments
were uniform in revealing the influence of androgens and estrogens—
depending on the situation—on the display of aggressive or dominance
behavior. At the time of maximal genital swelling or following treatment
of ovariectomized individuals with estradiol benzoate, female chimpanzees were dominant in competitive trials for a food reward (350-353
and several older reports from the Yerkes Laboratory of Primate Biology). A castrated male receiving the same estrogen became subordinate,
but when he was given methyl testosterone at a time when he was the
dominant member of a pair, his dominance became enhanced (350).
After similar treatment a subordinate female obtained most of the food.
The aggressiveness of male rats and mice largely disappeared following
castration (354—358) and it was increased or restored by injections of
testosterone propionate (355-357, 359, 360). The manner of action of
androgens and estrogens in producing these varied effects is not known.
The problem is complicated by the sudden remission of aggressive behavior at the time of estrus in female guinea pigs, hamsters, short-tailed
shrews, and probably many other mammals (78-80) when estrogen levels
are thought to be at their highest. The observation by Kislak and Beach
(80) that the administration of progesterone to an estrogen-conditioned
and aggressive female hamster is followed immediately by a loss of the
aggressiveness is an important lead, but its relevance for the broader
problem is not now apparent.
The relationship of the hormones to nest building and parental behavior has been reviewed (7). The subject is complex, many of the
results are contradictory, and no more than tentative conclusions are
justified. Two points made early in the review are important and will
be repeated here. The temporal relationships between ovulation, on the
one hand, and mating, nest building, and parental behavior, on the other,
are different in birds and mammals. In birds nest building, mating, and