Abstract
How are the image statistics of global image contrast computed? We answered this by using a contrast-matching task for checkerboard configurations of ‘battenberg’ micro-patterns where the contrasts and spatial spreads of interdigitated pairs of micro-patterns were adjusted independently. Test stimuli were 20 × 20 arrays with various sized cluster widths, matched to standard patterns of uniform contrast. When one of the test patterns contained a pattern with much higher contrast than the other, that determined global pattern contrast, as in a max() operation. Crucially, however, the full matching functions had a curious intermediate region where low contrast additions for one pattern to intermediate contrasts of the other caused a paradoxical reduction in perceived global contrast. None of the following models predicted this: RMS, energy, linear sum, max, Legge and Foley. However, a gain control model incorporating wide-field integration and suppression of nonlinear contrast responses predicted the results with no free parameters. This model was derived from experiments on summation of contrast at threshold, and masking and summation effects in dipper functions. Those experiments were also inconsistent with the failed models above. Thus, we conclude that our contrast gain control model (Meese & Summers, 2007) describes a fundamental operation in human contrast vision.
Highlights
Objects are sometimes erroneously seen as faces
What determines where we put our feet when walking on a pavement covered in slippery leaves? Do we choose dry patches to avoid slipping or step on leaves to avoid losing balance? To start answering such questions, we investigated the impact of perceptual grouping on foot placement: participants performed a stepping stone task in which pathways consisted of targets placed for optimal balance, with visual distractors in their proximity
Our results demonstrated that participants failed to follow the switching-in-depth targets if all targets were presented on a single plane from the beginning of each trial; participants could track the switching-in-depth targets if they appeared on both planes at the beginning
Summary
Objects are sometimes erroneously seen as faces (pareidolia phenomenon). We investigated whether seeing objects as faces would affect object detection performance. Inter-Stimuli-Interval (ISI) thresholds of distinguishing temporal double-pulse in positive and negative luminance contrast, isoluminance red–green contrast, and isoluminance blue–yellow contrast (denoted by LM+, LM-, L-/M+, L+/M-, S-/LM+, and S+/LM-, respectively) and in 0, 2, and 8 cpd spatial frequencies were measured from 13 normal color vision observers at intensities of single-pulse detection threshold (95% correct answer) of corresponding six directions individually and at two times of pulse duration of the single-pulse under less than 3% display error of the CIE (2006) tristimulus values L, M, and S.
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