Asymmetric Categorization in the Sequential Auditory Domain

An unusual category learning asymmetry in infants was observed by Quinn et al. (1993). Infants who were initially exposed to a series of pictures of cats and then were shown a dog and a novel cat, showed significantly more interest in the dog than in the cat. However, when the order of presentation was reversed — i.e., dogs were seen first, then a cat and a novel dog — the cat attracted no more attention than the novel dog. A series of experiments and simulations seemed to show that this asymmetry was due the perceptual inclusion of the cat category within the dog category because of the greater perceptual variability of dogs compared to cats (Mareschal & French, 1997; Mareschal et al., 2000; French et al., 2001, 2004). In the present paper, we explore whether this asymmetric categorization phenomenon generalizes to the auditory domain. We developed a series of sequential auditory stimuli analogous to the visual stimuli in Quinn et al. Two experiments on adult listeners using these stimuli seem to demonstrate the presence of an identical asymmetric categorization effect in the sequential auditory domain. Furthermore, we simulated these results with a connectionist model of sequential learning. Together with the behavioral data, we can conclude from this simulation that, as in the infant visual categorization experiments, purely bottom-up processes were largely responsible for our results.