Perceptual learning and face recognition : Disruption of second order relational information reduces the face inversion effect

Perceptual learning and face recognition : Disruption of second order relational information reduces the face inversion effect. Ciro Civile (cc413@exeter.ac.uk) School of Psychology, College of Life and Environmental Sciences, University of Exeter, UK. R.P. McLaren (R.P.McLaren@exeter.ac.uk) School of Psychology, College of Life and Environmental Sciences, University of Exeter, UK. I.P.L. McLaren (I.P.L.McLaren@exeter.ac.uk) School of Psychology, College of Life and Environmental Sciences, University of Exeter, UK. Abstract The face inversion effect is a reduction in recognition performance for inverted faces compared to upright faces that is greater than that typically observed with other stimulus types (e.g. houses; Yin, 1969). This study investigated the link between second-order relational structure and the face inversion effect suggested by Diamond and Carey (1986). The idea is that expertise gained as a consequence of a great deal of experience with exemplars derived from a familiar category, that possess what Diamond and Carey term second order relational structure, can produce an improved ability to distinguish between and recognise members of this category. Because facial features share the same basic spatial configuration, i.e. eyes are always above the nose and so on, and individual faces vary these spatial arrangements slightly, they have second order relational structure. The argument is that our experience with this structure underpins our ability to recognize faces, and this expertise with faces is lost on inversion because inversion disrupts the ability to exploit second order relational information. In this paper we report two experiments that confirm that we can obtain a strong face inversion effect, and that the magnitude of this effect can be reduced by disrupting the second order relational structure of the faces. Keywords: Inversion effect; face recognition; Thatcher illusion; scrambled faces; expertise; perceptual learning. Introduction Recognition of objects that are usually seen in one orientation is sometimes strongly impaired when the same objects are turned upside down, showing how intrinsically difficult it is to identify them. This has been found to be particularly the case for faces, a phenomenon known as the face inversion effect. (Yin,1969). Thus, the fact that recognition of human faces is more impaired by inversion than is recognition for other stimuli has underlined how faces are, in some sense, special. Over the past two decades, however, more behavioural evidence has emerged that challenges the assumption that facial stimuli are special, not the least of which is the demonstration that the inversion effect on recognition memory can be as strong with dogs as with faces when the subjects are experts in the identification and assessment of specific dog breeds. Given that the only stimuli that result in a substantial inversion effect are the ones for which the subjects have the necessary expertise (Diamond & Carey, 1986), this suggests that the face inversion effect may not be due to the fact that facial stimuli are subject to special processing because they are facial in nature, but instead that there are other factors, such as expertise, which give rise to this effect. Diamond and Carey (1986) proposed that it is a special type of information “second order relational information” that we depend on with increasing expertise. Human faces all have the same group of features (eyebrows, eyes, nose, mouth, etc.). All faces tend to have in common the same basic disposition of components, such that the eyes are always above the nose and so on. Thus, “first order relational information” corresponds to the spatial relationship between these features of a face, and “second order relational information” corresponds to the small variations in these spatial relationships that individuate the faces. In one of their experiments on detecting grotesqueness, Searcy and Bartlett (1996) made faces grotesque by either changing local elements, such as blackening teeth, blurring the pupils, or by changing the facial configuration. When shown in an inverted orientation, faces that were distorted by means of configural changes seemed to be more similar to the normal version while the “locally distorted face” still looked grotesque. Thus, configural changes did not survive the inversion process as well as local ones. In another experiment, Leder and Bruce (1998) distorted faces so as to be more distinctive, either changing local features by giving them darker lips, bushier eye brows, etc. or by changing configural information to give a shorter mouth to nose