Behavioral asymmetries in visual learning of young chickens.

Two-week-old chicks were trained in a simultaneous color discrimination learning task using food reinforcement. They had to discriminate between two discs of a different color whose right-left position was alternated at random. Results showed that chicks made more errors when the nonreinforced color was placed on the left with respect to the animal's body rather than when it was placed on the right. When chicks were trained on a right-left discrimination with two discs of identical color the asymmetry disappeared. Results are discussed in relation to current evidence for functional lateralization in the avian brain.