: 250 words,

The authors investigated how human adults encode and remember parts of multielement scenes composed of recursively embedded visual shape combinations. The authors found that shape combinations that are parts of larger configurations are less well remembered than shape combinations of the same kind that are not embedded. Combined with basic mechanisms of statistical learning, this embeddedness constraint enables the development of complex new features for acquiring internal representations efficiently without being computationally intractable. The resulting representations also encode parts and wholes by chunking the visual input into components according to the statistical coherence of their constituents. These results suggest that a bootstrapping approach of constrained statistical learning offers a unified framework for investigating the formation of different internal representations in pattern and scene perception.

Abstract not found

This paper compares the ability of human observers to detect target image curves with that of an ideal observer. The target curves are sampled from a generative model which specifies (probabilistically) the geometry and local intensity properties of the curve. The ideal observer performs Bayesian inference on the generative model using MAP estimation. Varying the probability model for the curve geometry enables us investigate whether human performance is best for target curves that obey specific shape statistics, in particular those observed on natural shapes. Experiments are performed with data on both rectangular and hexagonal lattices. Our results show that human observers ’ performance approaches that of the ideal observer and are, in general, closest to the ideal for conditions where the target curve tends to be straight or similar to natural statistics on curves. This suggests a bias of human observers towards straight curves and natural statistics. 1

Abstract. The visual system consists of parallel processing channels whose separation, proposed by psychophysicists, is sometimes doubted in view of the multi-modal responses of many visual cortical neurons. Thus psychophysical experiments should be designed to test critically whether or not the threshold detection mechanisms are independent and can serve to identify those stimuli that are detected. To achieve this aim the stimuli should be selective to the mechanisms tested, with minimum intrusions due to the activation of the other mechanisms. Threshold performance is examined using psychometric functions evaluating both probability of detection and discrimination and then computing thresholds for both. A 'labelled detector ' is defined when the detection and discrimination thresholds are close; for example, edge and line can be identified at their detection thresholds. Spatial arrangements of line and edge detectors can be mapped using a method of subthreshold summation (the 'dipper effect'). Additional techniques (incremental threshold, masking, pedestal, adaptation and coherence of compound stimuli) aim to reveal possible interactions between various mechanisms. The psychophysical

In the well-known Fraser illusion, a line composed of tilted elements itself appears tilted. The standard explanation of this illusion has been that the global orientation of the line is in some way influenced by the local orientation of the elements. The illusion was recreated using a texture composed of collinear Gabor stimuli, which were vertical. There was no local tilt. The illusory tilt was produced by gradually shifting the phase of the successive Gabors along each line. Although the 2D Fourier transform of this global pattern peaks at off-vertical orientations, the local energy of the patches is predominantly vertical. How does the visual system nevertheless pick up this global information? This can be explained by elongated linear filters, or a phase-tuned second-stage mechanism. We examined the first theory using a stereoscopic demonstration. When lines of opposite tilt are presented in the two eyes, they combine binocularly to produce stereoscopic slant. We tested whether th...

Note: This is a pre-publication draft (dated June 9, 2012) of the first paper of a twin set of review papers accepted for publication in Psychological Bulletin. Please cite as Wagemans, J., Elder, J. H.,