Response of male and female domestic chicks to change in the number (quantity) of imprinting objects

Abstract

When facing two sets of imprinting objects of different numerousness, domestic chicks prefer to approach the larger one. Given that choice for familiar and novel stimuli in imprinting situations is known to be affected by the sex of the animals, we investigated how male and female domestic chicks divide the time spent in the proximity of a familiar versus an unfamiliar number of objects, and how animals interact (by pecking) with these objects. We confirmed that chicks discriminate among the different numerousnesses, but we also showed that females and males behave differently, depending on the degree of familiarity of the objects. When objects in the testing sets were all familiar, females equally explored both sets and pecked at all objects individually. Males instead selectively approached the familiar numerousness and pecked more at it. When both testing sets comprised familiar as well as novel objects, both males and females approached the larger numerousness of familiar objects. However, chicks directed all their pecks toward the novel object within the set. Differences in the behavior of males and females can be accounted for in terms of sex difference in the motivation to reinstate social contact with the familiar objects and to explore novel ones, likely associated with the ecology and the social structure of the species before domestication.

A Kaspar Hauser experiment for innateness of numerical cognition

“…Their preference was immediately apparent at first choice, as well as in the overall percentage of time spent close to one or other of the two stimuli. As predicted, the two sexes expressed their preferences in different directions – for fixed numerousness in females and for changing numerousness in males – as noted (Introduction) it is well-documented in this species that males are more attracted by novelty 24–28 .…”

Resurgence of an Inborn Attraction for Animate Objects via Thyroid Hormone T3

“…From the second day of life, precocious sexually dimorphic behaviours start to emerge in chicks (Andrew, 1966). Due to different levels of social motivation and aggression, males and females exhibit different attitudes towards familiar and unfamiliar individuals (Cailotto et al, 1989;Vallortigara et al, 1990;Vallortigara, 1992;Versace et al, 2017;Lemaire et al, 2020;Santolin et al, 2020). Progressively, females develop strong social cohesive behaviours with familiar subjects, while males engage more in aggressive and explorative ones (McBride and Foenander, 1962;McBride et al, 1969).…”

Imprinting on time-structured acoustic stimuli in ducklings

“…In summary, the existence of sensitivity to an organizational property of stimuli, together with a strong effect of prior predispositions, confirms the view that even in this specialized, unreinforced form of learning the representation of information in the brain takes the form of concept vectors with multiple attributes that make it possible generalization towards stimuli that are identified by abstract rather than direct perceptual properties. With hindsight, and by contrasting our methods with protocols more widely used with research on imprinting in chickens (21)(22)(23)(24)(25)(26), it is to be expected that clearer evidence of generalization would result from longer imprinting exposures.…”