DO CHICKS RELY ON GEOMETRICAL OR NUMERICAL INFORMATION WHEN PECKING AT THE CENTRAL IN A LINE OF IDENTICAL BEADS ?

Abstract

Young chicks were trained (for food reinforcement) to peck at the central in a line made of nine identical and equally space beads. During training the central bead was of a different colour, at test all beads were identical. Generalisation tests were also run with modified versions of the stimulus, obtained by changing the spacing between the single beads, so that the numerical and geometrical centres did not coincide. With the symmetrical stimulus chicks pecked the central bead significantly above chance, hence they were able of identifying such position exclusively on the base of spatial (possibly numerical) cues. With asymmetrical stimuli birds chose to peck either the numerical or the geometrical centre, depending on the distribution of inter-beads spacing, and on possible perceptual grouping.