Testosterone (T) administration in young chicks induces an adult-like morphology and a number of adult-like behaviors including crowing and aggressive pecking, and a decrease in the distress vocalization (DV) which normally accompanies social separation. The present series of studies investigated some of these T-induced emotional effects, with an analysis of gender differences. Effects of drugs known to modulate vocalizations were also assessed. When tested in groups of four, control males were three times more aggressive than females. T-treatment raised that level of aggression in females up to the level of males. T-treated males crowed four times more often than treated females, while no control chicks of either gender ever crowed. Scopolamine (1mg/kg) decreased crowing slightly, but had no effect on pecking. When chicks were tested individually, T-treatment decreased the number of DVs emitted, with males more affected than females. Scopolamine increased the number of DVs emitted in all test groups. Morphine (1mg/kg) had no effect on either pecking or crowing, but reduced the number of DVs in males and females in both treatment conditions. While naloxone (1mg/kg) had no effects on DVs, it blocked the morphine-induced suppression of vocalization. Males were also tested by being paired with a like-treated weight-matched chick from their same small flock or from a different flock. Chicks crowed over eight times more often and pecked each other fives times more often when they were paired with a stranger than with a fellow from their own flock.