Abstract
Predispositions of newborn vertebrates to preferentially attend to living beings and learn about them are pervasive. Their disturbance (e.g. in neonates at risk for autism), may compromise the proper development of a social brain. The genetic bases of such predispositions are unknown. We use the well-known visual preferences of newly-hatched chicks (Gallus gallus) for the head/neck region of the 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 breeds maintained genetically isolated for at least eighteen years while identically raised. Visually-naïve chicks of all 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 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 hence documented the presence of inherited genetic variability in the expression of early social predispositions in interaction with environmental stimuli.
Highlights
Predispositions of newborn vertebrates to preferentially attend to living beings and learn about them are pervasive
It has been shown that neonates at high familiar risk of developing Autism Spectrum Disorders exhibit significantly weaker preferences for attending biological motion and face-like stimuli compared to low risk neonates taken from the general population[11]
Some of the stimuli used for testing human neonates have been first investigated in non-human models[5,12], showing the relevance and translational value of studies on early predispositions for animate objects in biomedical research
Summary
When considering the performance of the three breeds across time, as shown, the scenario appears much different: at the very beginning of their visual experience (minutes of test 0–5), there was no significant difference between breeds (chi-squared2 = 2.856, p = 0.240) but we observed an overall significant preference for the stuffed hen (V = 3120, p < 0.001) In their first moments of life all breeds were attracted by the stimulus that presented more animacy cues, showing a predisposition for the stuffed hen over the scrambled hen. In the wild, chicks can usually approach the naturalistic stimuli to which they direct their affiliative responses, and receive visual, tactile and acoustic feedback[27,28] This feedback is very important to maintain proximity with the stimulus and induce the filial imprinting process. Given that our test is performed at the very beginning of the imprinting process, a change in preferences during the test after a first orienting response towards the predisposed stimulus is consistent with the ethological needs of the filial imprinting process[30,36]
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