Newborn chicks show inherited variability in early social predispositions for hen-like stimuli

Abstract

Predispositions of newborn vertebrates to preferentially attend to living beings and learn about them are pervasive. Their disturbance (e.g. in human neonates at risk for autism), may compromise the proper development of a social brain. The genetic bases of such predispositions are unknown. Here we take advantage of well-known visual preferences exhibited by newly-hatched domestic chicks (Gallus gallus) for the head/neck region of their mother hen, to investigate the presence of segregating variation in the predispositions to approach a stuffed hen vs. a scrambled version of it. We compared the spontaneous preferences of three different breeds that have been maintained genetically isolated for at least eighteen years and identically raised in the same farm. Visually-naive chicks of all the three tested breeds (Padovana, Polverara and Robusta maculata) showed the same initial preference for the predisposed stimulus, suggesting that the direction of the initial preference might be genetically fixed. A few minutes later though, striking differences emerged between breeds, which could indicate early different strategies of dealing with affiliative objects: while the Polverara breed maintained a constant preference across the entire test, the Padovana and Robusta breeds progressively explored the alternative stimulus more. We argue that exploration of novelty might help chicks to look for responsive parental objects and to form a more structured representation of the mother hen. We hence documented the presence of inherited genetic variability for early social predisposition in interaction with environmental stimuli.