Spatial content of faces may be critical for individualizing faces

Abstract

Many of the phenomena associated with face (vs. object) recognition can be understood in terms of a representation for individuating faces that retains aspects of the original spatial filter activations, as posited by Malsburg's Gabor Jet model that mimics the functions of the columns of V1 simple cells. Objects, in contrast, may be represented by a structural description specifying explicit relations among view invariant properties of edges of simple parts. Subjects judged whether a sequentially presented pair of images was the face of the same person, in one condition, or the same chair, in another (Biederman & Kalocsai, 1997). The images were filtered (in the Fourier domain) into 8 scales and 8 orientations. Complementary pairs of each person or chair image were created by assigning the content of every other combination of scale and orientation to a given image. (If the scales are ordered as rows and the orientations as columns to form a checkerboard, then one member of a complementary pair would have the content from the red squares and the other member the content from the black squares.) On half the matching trials (i.e., the same chair or the same person), the images were complements; on the other half they were identical. Consistent with the hypothesis that face representations retained the original spatial content, matching complements of faces resulted in markedly greater error rates and RTs than the identical images. No such costs were apparent when matching chairs. However, the chairs different in small parts that could be discerned from their edges. The present study examined the costs of complementizing smooth, non-face, blobby objects (variations in the amplitudes of the harmonics of a sphere) that differed from each other metrically, as did the faces. A cost of complementizing was observed for the blobs but this cost was smaller than that for the faces. The necessity to make fine metric judgments of smooth surfaces may underlie part of the sensitivity of faces to the spatial content of the image