EISEVIER Behavioural Processes 37 (1996) 67-74 Lateral asymmetries during responses to novel-coloured objects in the domestic chick: A developmental study Lucia Regolin ‘, Giorgio Vallortigara bT * a Dipartimento di Psicologia Generale, Uniuersith di Padoua, Piazza Capitaniato 3, 35139 Padoua, Italy h Istituto di Filosojia, Pedagogia, Didattica delle Lingue Modeme. Unicersitic di l/dine, Via Antonini 8, 33100 Udine. Italy Accepted 4 October 1995 Abstract Chicks were trained to peck on a small coloured (red or green) box for food reinforcement. They were then presented with one box identical to that used during training (familiar) and one of a different colour (unfamiliar). Food reinforcement was delivered for pecking either box, and the right-left position of the two boxes was alternated at random between trials. The number of times chicks pecked at the novel box when it was located on their right or on their left side was recorded. Chicks showed a general tendency to peck more frequently at the novel box when it was located on their right side. The lateral asymmetry was, however, age-dependent. Maximum lateral bias with both red and green novel boxes was observed at around day 4 and day 11 in both sexes, and minimum at around days 7/8 in males and days 8/9 in females. It is suggested that these lateral asymmetries can be accounted for in terms of a head-and-body turning bias associated to preferential use of the lateral field of vision of the left eye, which arises from specializations of the contralateral brain structures (i.e. right hemisphere involvement in response to novelty). The observed changes in lateral asymmetries during development appear, in fact, to lit very well with independent behavioural and pharmaco- logical evidence for biases to left eye use on day 11, and right eye use on day 8. Keywords: Lateralization; Development of lateralization; Novelty; Chick; Callus gallus domesticus 1. Introduction Lateralization of brain functions is well attested in the domestic chick. A variety of behavioural (Andrew, 1983, 19911, pharmacological (Rogers, 1991, 1995) and neurobiological (Horn, 1990; Rose, 1992) methods has revealed that the two hemispheres differ in fundamental ways in modes of analysis and storage of perceptual information. * Corresponding author. E-mail: Giorgio.Vallortigara@Ifp.Uniud.It 0376.6357/96/$15.00 0 1996 Elsevier Science B.V. All rights reserved SSDIO376-6357(95)00076-3