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Hans Strasburger; Unfocussed spatial attention underlies the crowding effect in indirect form vision. Journal of Vision 2004;4(8):659. doi: https://doi.org/10.1167/4.8.659.
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© ARVO (1962-2015); The Authors (2016-present)
When targets are seen in the presence of neighbouring patterns or contours, their visibility is reduced. This phenomenon, known as the crowding effect, is particularly pronounced in indirect view. By the measurement of recognition contrast sensitivity of a character with flankers to the left and right, we studied mechanisms underlying the crowding effect in indirect form vision. Attentional and featural contributions to the effect can be separated by a new paradigm that distinguishes pattern location errors from pattern recognition errors and further by manipulating the focussing of spatial attention through a transient positional cue, appearing 150 ms before the target. Measurements were on the horizontal meridian, at 1, 2, and 4 eccentricity, and a range of flankers' distances. Our results show that in normal indirect view the impairment of character recognition by crowding is — in particular at intermediate flanker distances — caused by spatially imprecise focussing of attention. The enhancement of performance by a transient positional cue seems mediated separately such that locus and intensity are independent characteristics of attention in form vision.
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