Stanley A. Klein

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When a vernier target is flanked by optimally positioned lines, foveal vernier discrimination is strongly degraded (Westheimer and Hauske, 1975). We confirmed this observation (Experiment I) and have mapped out a 2 dimensional "perceptive field" for crowding in the fovea using a 2 dot target (Experiment II). Crowding was also measured in peripheral vision,(More)
Practice improves discrimination of many basic visual features, such as contrast, orientation, and positional offset. Perceptual learning of many of these tasks is found to be retinal location specific, in that learning transfers little to an untrained retinal location. In most perceptual learning models, this location specificity is interpreted as a(More)
The psychometric function, relating the subject's response to the physical stimulus, is fundamental to psychophysics. This paper examines various psychometric function topics, many inspired by this special symposium issue of Perception & Psychophysics: What are the relative merits of objective yes/no versus forced choice tasks (including threshold(More)
SIR — Interceptive actions, such as hitting a moving target or catching a ball, need to be adequately timed in order to be successful. Because there is a significant time delay in the transmission of information along the visual pathways, there could be a critical difference between the perceptual and actual position of a moving object. Nijhawan proposed(More)
Spatial interactions are a critical and ubiquitous feature of spatial vision. These interactions may be inhibitory (reducing sensitivity as occurs in crowding) or facilitatory (enhancing sensitivity). In this work, we had four goals. 1. To test the hypothesis that foveal crowding depends on target size by measuring the extent of crowding for novel targets(More)
Unlike most visual tasks, contrast discrimination has been reported to be unchanged by practice (Dorais & Sagi, 1997; Adini, Sagi, & Tsodyks, 2002), unless practice is undertaken in the presence of flankers (context-enabled learning, Adini et al., 2002). Here we show that under experimental conditions nearly identical to those in the no-flanker practice(More)
Visual perceptual learning models, as constrained by orientation and location specificities, propose that learning either reflects changes in V1 neuronal tuning or reweighting specific V1 inputs in either the visual cortex or higher areas. Here we demonstrate that, with a training-plus-exposure procedure, in which observers are trained at one orientation(More)
Visual evoked potentials (VEPs) to luminance and pattern reversal stimulation were derived for a large number of small areas throughout the central visual field. In one study, the field was tested with a stimulus array consisting of 64 equal-area patches. Local response components were extracted by independent m-sequence modulation of the patches. Field(More)
1. We have analyzed receptive fields (RFs) of directionally selective (DS) complex cells in the striate cortex of the cat. We determined the extent to which the DS of a complex cell depends on spatially identifiable subunits within the RF by studying responses to an optimally oriented, three-luminance-valued, gratinglike stimulus that was spatiotemporally(More)
Amblyopic vision is characterized by reduced spatial resolution, and inhibitory spatial interactions ("crowding") that extend over long distances. The present paper had three goals: (1) To ask whether the extensive crowding in amblyopic vision is a consequence of a shift in the spatial scale of analysis. To test this we measured the extent of crowding for(More)