Supplementary Materials and Methods from Early life manipulations of vasopressin-family peptides alter vocal learning

Vocal learning from social partners is crucial for the successful development of communication in a wide range of species. Social interactions organize attention and enhance motivation to learn species-typical behaviour. However, the neurobiological mechanisms connecting social motivation and vocal learning are unknown. Using zebra finches (<i>Taeniopygia guttata</i>), a ubiquitous model for vocal learning, we show that manipulations of non-apeptide hormones in the vasopressin family (arginine vasotocin (AVT)) early in development can promote or disrupt both song and social motivation. Young male zebra finches, like human infants, are socially gregarious and require interactive feedback from adult tutors to learn mature vocal forms. To investigate the role of social motivational mechanisms in song learning, in two studies, we injected hatchling males with AVT or Manning compound (MC, a non-apeptide receptor antagonist) on days 2–8 post-hatching and recorded song at maturity. In both studies, MC males produced a worse match to tutor song than controls. In Study 2, which experimentally controlled for tutor and genetic factors, AVT males also learned song significantly better compared with controls. Furthermore, song similarity correlated with several measures of social motivation throughout development. These findings provide the first evidence that non-apeptides are critical to the development of vocal learning.