Effects of testosterone on the calling of the domestic chick in a strange environment

Testosterone affects calling in a strange environment in two independent ways. In both sexes, short calls increase in number at the expense of peeps early in the test (when they would in any case be numerous) probably as a result of an increased tendency to repeat the call which has just been given. In males only, peeps are reduced in number during established calling, as a result of the interpolation of brief periods of silence. There is no accompanying depression of escape, but the visual scanning usual during peeps is reduced. The replacement of peeps by silence and immobility may be a consequence of an increase in persistence of attention to particular stimuli.