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Uncovering foveal crowding?

Lev M, Yehezkel O, Polat U - Sci Rep (2014)

Bottom Line: We hypothesized that limiting stimulus availability should decrease object recognition in clutter.Here we show, for the first time, that robust contour interactions exist in the fovea for much larger target-flanker spacing than reported previously: participants overcome crowded conditions for long presentations times but exhibit contour interaction effects for short presentation times.Our results suggest that contemporary models of context modulation should include both time and spatial processing.

View Article: PubMed Central - PubMed

Affiliation: Goldschleger Eye Research Institute, the Sackler Faculty of Medicine, Tel-Aviv University, Tel-Hashomer, Israel.

ABSTRACT
Visual crowding, as context modulation, reduce the ability to recognize objects in clutter, sets a fundamental limit on visual perception and object recognition. It's considered that crowding does not exist in the fovea and extensive efforts explored crowding in the periphery revealed various models that consider several aspects of spatial processing. Studies showed that spatial and temporal crowding are correlated, suggesting a tradeoff between spatial and temporal processing of crowding. We hypothesized that limiting stimulus availability should decrease object recognition in clutter. Here we show, for the first time, that robust contour interactions exist in the fovea for much larger target-flanker spacing than reported previously: participants overcome crowded conditions for long presentations times but exhibit contour interaction effects for short presentation times. Thus, by enabling enough processing time in the fovea, contour interactions can be overcome, enabling object recognition. Our results suggest that contemporary models of context modulation should include both time and spatial processing.

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Related in: MedlinePlus

Comparison of the contour interaction effect for different letter spacing: Data are presented for 11 new participants.a, c) The percentage correct (y axis) for the single (uncrowded, red line) and crowded (blue line) conditions are plotted against the stimulus duration (x axis). The letter size is 0.12 deg. and the letter spacing is one letter size (a) and 0.4 letters (c). There is a robust and significant effect of reduction in the percent correct at the short presentation times. c, d) The reaction time in msec (y axis) is plotted against the stimulus duration (x axis). The reaction time for the crowded conditions was always significantly and robustly slower for all presentation times.
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f2: Comparison of the contour interaction effect for different letter spacing: Data are presented for 11 new participants.a, c) The percentage correct (y axis) for the single (uncrowded, red line) and crowded (blue line) conditions are plotted against the stimulus duration (x axis). The letter size is 0.12 deg. and the letter spacing is one letter size (a) and 0.4 letters (c). There is a robust and significant effect of reduction in the percent correct at the short presentation times. c, d) The reaction time in msec (y axis) is plotted against the stimulus duration (x axis). The reaction time for the crowded conditions was always significantly and robustly slower for all presentation times.

Mentions: To further explore this effect, we repeated the experiment with eleven new young participants using a smaller letter size (0.12 deg., 7.2 arc min, VA = 0.22 LogMar) and target-flanker spacing of either one letter size (Figure 2a) or 0.4 letter size (Figure 2c). Like in Figure 1b, the results show a sign of contour interaction for presentation times of 30 and 60 msec for single letter spacing (Figure 2a) in which the percentage correct is reduced slightly but significantly only for 30 msec (from 90 to 86 percent correct; paired t-test, p = 0.019). However, for 0.4 letter spacing, the effect is remarkably and significantly apparent for all presentation times (paired t-test, p < 0.0005 for presentation times of 30, 60, 120; p = 0.02 presentation time = 240 msec). Here also the reaction time (Figures 2c, d) clearly shows that there is a consistent and significant reduction (paired t-test, p < 0.0005 for all presentation times) of about 50 msec (one letter spacing) and about 100 msec (0.4 letter spacing) under the crowded conditions for all presentation times. These results support the idea that extra processing time is required to overcome the effect of contour interaction in the fovea.


Uncovering foveal crowding?

Lev M, Yehezkel O, Polat U - Sci Rep (2014)

Comparison of the contour interaction effect for different letter spacing: Data are presented for 11 new participants.a, c) The percentage correct (y axis) for the single (uncrowded, red line) and crowded (blue line) conditions are plotted against the stimulus duration (x axis). The letter size is 0.12 deg. and the letter spacing is one letter size (a) and 0.4 letters (c). There is a robust and significant effect of reduction in the percent correct at the short presentation times. c, d) The reaction time in msec (y axis) is plotted against the stimulus duration (x axis). The reaction time for the crowded conditions was always significantly and robustly slower for all presentation times.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3921636&req=5

f2: Comparison of the contour interaction effect for different letter spacing: Data are presented for 11 new participants.a, c) The percentage correct (y axis) for the single (uncrowded, red line) and crowded (blue line) conditions are plotted against the stimulus duration (x axis). The letter size is 0.12 deg. and the letter spacing is one letter size (a) and 0.4 letters (c). There is a robust and significant effect of reduction in the percent correct at the short presentation times. c, d) The reaction time in msec (y axis) is plotted against the stimulus duration (x axis). The reaction time for the crowded conditions was always significantly and robustly slower for all presentation times.
Mentions: To further explore this effect, we repeated the experiment with eleven new young participants using a smaller letter size (0.12 deg., 7.2 arc min, VA = 0.22 LogMar) and target-flanker spacing of either one letter size (Figure 2a) or 0.4 letter size (Figure 2c). Like in Figure 1b, the results show a sign of contour interaction for presentation times of 30 and 60 msec for single letter spacing (Figure 2a) in which the percentage correct is reduced slightly but significantly only for 30 msec (from 90 to 86 percent correct; paired t-test, p = 0.019). However, for 0.4 letter spacing, the effect is remarkably and significantly apparent for all presentation times (paired t-test, p < 0.0005 for presentation times of 30, 60, 120; p = 0.02 presentation time = 240 msec). Here also the reaction time (Figures 2c, d) clearly shows that there is a consistent and significant reduction (paired t-test, p < 0.0005 for all presentation times) of about 50 msec (one letter spacing) and about 100 msec (0.4 letter spacing) under the crowded conditions for all presentation times. These results support the idea that extra processing time is required to overcome the effect of contour interaction in the fovea.

Bottom Line: We hypothesized that limiting stimulus availability should decrease object recognition in clutter.Here we show, for the first time, that robust contour interactions exist in the fovea for much larger target-flanker spacing than reported previously: participants overcome crowded conditions for long presentations times but exhibit contour interaction effects for short presentation times.Our results suggest that contemporary models of context modulation should include both time and spatial processing.

View Article: PubMed Central - PubMed

Affiliation: Goldschleger Eye Research Institute, the Sackler Faculty of Medicine, Tel-Aviv University, Tel-Hashomer, Israel.

ABSTRACT
Visual crowding, as context modulation, reduce the ability to recognize objects in clutter, sets a fundamental limit on visual perception and object recognition. It's considered that crowding does not exist in the fovea and extensive efforts explored crowding in the periphery revealed various models that consider several aspects of spatial processing. Studies showed that spatial and temporal crowding are correlated, suggesting a tradeoff between spatial and temporal processing of crowding. We hypothesized that limiting stimulus availability should decrease object recognition in clutter. Here we show, for the first time, that robust contour interactions exist in the fovea for much larger target-flanker spacing than reported previously: participants overcome crowded conditions for long presentations times but exhibit contour interaction effects for short presentation times. Thus, by enabling enough processing time in the fovea, contour interactions can be overcome, enabling object recognition. Our results suggest that contemporary models of context modulation should include both time and spatial processing.

Show MeSH
Related in: MedlinePlus