Use of property/kind information for object individuation in young chicks (Gallus gallus)

Object individuation is the process by which organisms establish the number of distinct objects present in an event. Previous research demonstrated that chicks are able to use spatiotemporal and property information for object individuation. The ability to use property/kind information is assessed employing imprinting objects and food items (i.e. mealworms). Newborn chicks were reared with 5 identical imprinting objects. On day 2 each chick underwent a free choice test in which 2 groups of events were shown: a group comprised two stimuli i.e. an imprinting object and a food item; the second group was composed by a single stimulus (i.e. either imprinting object or food item) presented twice (Exp.1). Each stimulus in each group of events was sequentially presented and concealed in the same spatial location; each group of events took place in a different spatial location and the number of events was equalized. Chicks (N=24) spontaneously approached the two different stimuli rather than the single stimulus seen twice. A possible preference for the more varied set of stimuli was excluded by testing chicks (N=12) in a simultaneous presentation of two imprinting objects vs two food items (Exp.2).