Sensitivity to spatial frequency and orientation content is not specific to face perception

Abstract

Prior work using a matching task between images that were complementary in spatial frequency and orientation information suggested that the representation of faces, but not objects, retains low-level spatial frequency (SF) information [Biederman, I., & Kalocsai, P. (1997). Neurocomputational bases of object and face recognition. Philosophical Transactions of the Royal Society of London, Series B Biological Sciences, 352, 1203-1219]. In two experiments, we reexamine the claim that face perception is uniquely sensitive to changes in SF. In contrast to prior work, we used a design allowing the computation of sensitivity and response criterion for each category, and in one experiment, equalized low-level image properties across object categories. In both experiments, we find that observers are sensitive to SF and orientation changes for upright and inverted faces and non-face objects. Differential response biases across categories contributed to a larger sensitivity for faces, but even sensitivity showed a larger effect for faces, especially when faces were upright and in a front-facing view. However, when objects were inverted, or upright but shown in a three-quarter view, the matching of objects and faces was equally sensitive to SF changes. Accordingly, face perception does not appear to be uniquely affected by changes in spatial filter components.

Figure 1

Spatial Frequency (SF) and Orientation filtering. Two complementary images were created by filtering a single input image in the Fourier domain into an 8 by 8 radial matrix of SF-orientation information. Two separate filters were applied to preserve alternating combinations of the SF-orientation content of the original image. Thus, when returned to the spatial domain via inverse FFT, the complementary pair of images share no overlapping combinations of SF and orientation information.

Figure 2

Example images from Experiment 1. Displayed are pairs of filtered and SHINEd exemplars from each object category (face, car, chair).

Figure 3

Experiment 1 results (N=34). (a) Mean values for same-different matching of identical and complementary faces, cars, and chairs presented either upright or inverted are represented using three dependent measures: accuracy for same trials, sensitivity (d′), and response criterion (C). For each orientation of all stimulus categories using both accuracy and d′ measures, subjects were significantly better matching Identical relative to Complementary pairs of images. Error bars represent the standard error of the mean. (b) The CE (Identical – Complementary) associated with accuracy, d′ and C measurements is plotted for upright and inverted faces, cars, and chairs. Error bars represent standard error of the mean.

Figure 4

Example images from Experiment 2. Displayed are pairs of filtered images from each target category (0°- and 45°-view faces and chairs).

Figure 5

Experiment 2 results (N=30). (a) Mean values for same-different matching of identical and complementary faces and chairs at either 0° rotation or 45° rotation are represented using three dependent measures: accuracy for same trials, sensitivity (d′), and response criterion (C). Error bars represent standard error of the mean. (b) The CE (Identical – Complementary) associated with accuracy, d′ and C measurements is plotted for 0° and 45° views of faces and chairs. Error bars represent standard error of the mean.