Androgens and imprinting: differential effects of testosterone on filial preference in the domestic chick

The relation between testosterone and imprinting was investigated in domestic chicks. After hatching, chicks received either testosterone enanthate in oil or oil alone (controls). The chicks were then trained by exposing them to a rotating imprinting stimulus, either a red box or a stuffed jungle fowl. A preference score was then determined, providing a measure of the strength of imprinting. Plasma testosterone concentration after testing did not differ significantly between males and females and was unaffected by the type of training stimulus. In fowl-trained chicks, but not in box-trained chicks, preference score was positively correlated with plasma testosterone concentration. Furthermore, the mean preference score of the fowl-trained chicks that had received exogenous testosterone was significantly higher than that of their controls; no such effect was found in box-trained chicks. A previous study showed that imprinting with the box, but not the fowl, is profoundly impaired by a noradrenergic neurotoxin. The results taken together suggest that some of the neural systems supporting the preference for the red box, a simple artificial object, are different from some of those supporting the preference for the stuffed jungle fowl.