Imprinted numbers: newborn chicks’ sensitivity to number vs. continuous extent of objects they have been reared with

Abstract

Newborn chicks were tested for their sensitivity to number vs. continuous physical extent of artificial objects they had been reared with soon after hatching. Because of the imprinting process, such objects were treated by chicks as social companions. We found that when the objects were similar, chicks faced with choices between 1 vs. 2 or 2 vs. 3 objects chose the set of objects of larger numerosity, irrespective of the number of objects they had been reared with. Moreover, when volume, surface or contour length were controlled for using sets of 1 vs. 4, 1 vs. 6 or 1 vs. 3 objects, chicks resorted to choosing the larger object, rather than the familiar numerosity. When, however, chicks were reared with objects differing in their aspect (colour, size, and shape) and then tested with completely novel objects (of different colour and shape but controlled for continuous extent), they chose to associate with the same number of objects they had been reared with. These results suggest that identification of objects as different and separate individuals is crucial for the computation of number rather than continuous extent in numerical representation of small numerosities and provide a striking parallel with results obtained in human infants. Early availability of small numerosity discrimination by chicks strongly suggests that these abilities are in place at birth.

Quantity Discrimination in Domestic Rats, Rattus norvegicus

“…A key consideration in studies of quantity discrimination is ensuring that the findings cannot be explained by the species use of non-numerical cues [39,47,50]. In this study control conditions for olfactory cues, surface area and volume were utilized.…”

Beyond left and right: Automaticity and flexibility of number-space associations

“…Several observations were made providing good explanations regarding the origin of the association between numbers and space. These are for instance reading and writing directions (Dehaene et al, 1993;Shaki, Fischer, & Petrusic, 2009;Zebian, 2005), innate imbalance (Rugani, Regolin, & Vallortigara, 2010), or association of concepts on the basis of linguistic markedness (for a discussion, see Proctor and Cho, 2006). The dual route account does not refute any of these possibilities nor does it provide evidence favoring one or the other of these factors.…”

The development of support intuitions and object causality in juvenile Eurasian jays (Garrulus glandarius)

“…Evidence for core knowledge is further supported by studies with chicks ( Gallus gallus ), where early rearing experience can be controlled for in this precocial bird. Newly hatched chicks have intuitions about the physical properties of imprinted objects that can or cannot be occluded behind screens23, can reorient based on physical features of geometric structures they have not previously experienced24, and show a concept for numerosity when associating with a choice of differing numbers of objects (perceived as social agents through imprinting)25 (reviewed in ref. 26).…”