Testosterone, early experience and behavioral arousal in a novel environment

Rhode Island Red chicks were hatched either in isolation or in pairs. On the second day after hatching they were injected with either 0, 0.5, 1.5, 4.5, or 13.5 mg of testosterone. Two days later their emotional response to a novel environment was determined by counting the cheeping rate. It was found that, while low doses of testosterone elevated cheeping, the highest doses caused a depression back to, or below, control levels. The rearing environment also had an effect in that the isolated chicks cheeped more than their social counterparts for every dose except the 0.5-mg dose. It was concluded that testosterone can influence behavioral arousal in chicks but that the effect is dependent upon both dose and previous environmental experience.