Abstract
Overlay masking, lateral interactions, surround suppression, and crowding all reduce performance in many psychophysical tasks, but also show distinctive differences suggesting that they are separate processes with different neural substrates (Levi, 2008; Petrov, Popple & McKee, 2007). One difficulty in performing such a meta-analysis is the simultaneous variation of stimuli, experimental method, psychophysical task, and laboratory conditions across different studies. We describe a series of previously reported and new fine spatial frequency and orientation discrimination results that, taken together, do not fit neatly into any one of these categories. In all experiments, observers were highly trained, experienced undergraduates naïve to the purpose of the studies. In most studies, observers discriminated between 2 alternative sinusoidal patterns. On any one trial, a single stimulus was presented. Highly experienced, naïve observers rated their certainty, on a six-point-scale,that pattern A or B had been presented. Performance was measured in d'. In different studies, test and "mask" stimuli were overlaid, were center-surround patterns that abutted or not, were 1st order luminance-modulated gratings or 2nd order contrast-modulated gratings or a mixture, differed in apparent depth or were in the same plane,were in or out of phase, differed in mean luminance, etc. The collective results provide a rich set of more homogeneous data, collected under identical laboratory conditions in, to describe characteristics of the mechanisms underlying fine spatial discriminations. Our results cut across existing categorizations, suggesting either that current conceptualizations are not adequate, or that yet more processes need to be added to the mix.
Meeting abstract presented at OSA Fall Vision 2012