Perceptual learning for a familiar category under inversion: An analogue of face inversion?

Perceptual learning for a familiar category under inversion: An analogue of face inversion? I.P.L. McLaren( I.P.L.McLaren@exeter.ac.uk) School of Psychology, College of Life and Environmental Sciences, University of Exeter, UK. Ciro Civile (cc413@exeter.ac.uk) School of Psychology, College of Life and Environmental Sciences, University of Exeter, UK. Abstract This study investigated the link between expertise for a prototype- defined category and the face inversion effect (which refers to the decline in performance in recognising faces that are inverted compared to the recognition of faces in their normal upright orientation; e.g., Yin, 1969). We aimed to demonstrate an analogous effect in chequerboards drawn from a familiar category such that participants had acquired a certain expertise with that category. Participants in this study were first presented with a categorisation task in which they were asked to sort a number of chequerboards (in an upright orientation) into two categories. This increased their familiarity with these categories. Then, in the next (study) phase, participants were presented with a set of chequerboards which included exemplars (some upright, some inverted) from one of the two categories that participants were familiar with, plus exemplars (also upright or inverted) from a novel category. Following this, participants were presented with an old/new recognition task that included exemplars seen in the study phase plus new exemplars of the same (familiar and novel) categories in both orientations (upright and inverted). We succeeded in obtaining the same pattern of effects reported in McLaren (1997), i.e. a significant inversion effect for stimuli drawn from the familiar category, but with standard recognition procedures. We interpret the results in terms of McLaren and Mackintosh's (2000) theory of representation development. Keywords:Inversion; perceptual learning; expertise; faces; recognition; chequerboards; categorization; latent inhibition. Introduction The face inversion effect proper refers to the greater decline in performance in recognizing faces that are inverted compared to the recognition of faces in their normal upright orientation when contrasted with similar manipulations using other stimuli such as pictures of houses (Yin, 1969). On the basis of this effect it had been believed that faces were processed in our brain in a different way to other kinds of stimuli. The assumption that facial stimuli are special can be challenged by the demonstration that the inversion effect in recognition memory can be as strong with images of dogs as with faces when the subjects are experts in specific dog breeds (Diamond & Carey, 1986). Thus, this suggests that the face inversion effect may not be due to the fact that facial stimuli are separately processed by the brain, but instead that there are other factors, such as expertise, which give rise to this effect. Back in 1997 McLaren demonstrated that we can obtain a significant inversion effect analogous to that in faces with chequerboards drawn from a familiar category as long as they possess the appropriate stimulus structure. Subjects were exposed to a set of chequerboards and were asked to categorise them into two different prototype-defined categories. This was followed by a discrimination task which included two pairs of chequerboards (one pair in an upright and the other pair in an inverted orientation) from a familiar category, plus two control pairs of chequerboards from a novel category (again one pair upright the other inverted). The results showed that familiarity with a category defined by a prototype gave subjects an enhanced ability to discriminate between exemplars of that category in an upright orientation. This benefit was lost when the stimuli were inverted, to the extent that learning of the discrimination involving inverted familiar exemplars was worse than for appropriate controls. No inversion effect was found for exemplars taken from a novel category of chequerboards, or for chequerboards that were taken from a familiar category that was not prototype- based. In the same study McLaren (1997) tried to extend those results in a delayed matching task. Each trial of the delayed matching task involved a category exemplar being presented for 1 sec in either an upright or inverted orientation, and finally a second exemplar drawn from the same category and with the same orientation as the first. Subjects had to decide whether the second chequerboard was the same as or different from the first as rapidly as possible by pressing one of two keys. Trials were randomized with the constraint that half were positive (same) trials and half negative (different). Results showed that subjects presented with exemplars from a familiar category were significantly better at judging whether upright exemplars were the same or different than at making the same decision for the inverted exemplars. Finally performance on the familiar upright exemplars was significantly better than that for novel controls. Thus, experience with a category leads to a significant inversion effect in a matching task confirming the results obtained in the discrimination task. However this time performance on inverted familiar exemplars was not significantly worse than that on inverted novel exemplars. In the present study we aimed to replicate McLaren’s (1997) findings using a standard face recognition paradigm, but with chequerboards as stimuli rather than faces. The prediction was that expertise with members of a familiar, prototype-defined category would lead to an improved ability in distinguishing