Avian hatching as a strategy to test context-specific habituation

Whether habituation is a non-associative or an associative form of learning may depend on the perception of the context. In precocious avian species, the hatching moment represents a natural condition to investigate this issue. We exploited this possibility by measuring the stops of the wheel-running behavior to 2 sequences of 5 bursts white-noise, presented 1 hour apart, in 4 groups of chicks (Gallus gallus) during their second day of life. Critically, the perceived context of the first day of stimulation changed among the conditions: chicks were stimulated 1) within the egg, 2) in the incubator, 3) within the same running wheel, 4) chicks were naïve. We observed that chicks stimulated before hatching in the egg and after hatching in the incubator habituated to a lesser extent than chicks stimulated always in the same context (i.e. the running wheel), but to a significantly higher degree than that of naïve chicks, supporting an associative interpretation of the habituative phenomenon.