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Bilge Sayim, Michael M. Herzog, Gerald Westheimer; Contextual modulation of vernier thresholds by chromaticity-based grouping mechanisms. Journal of Vision 2007;7(9):907. doi: 10.1167/7.9.907.
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© ARVO (1962-2015); The Authors (2016-present)
In contextual modulation, neighbouring elements often impede performance on a target. For example, vernier offset discrimination deteriorates if lines flank the vernier. Explanations are usually based on local spatial interactions. However, we have recently shown that increasing the number of flanks can improve performance arguing against purely local interactions. We proposed instead that contextual interference diminishes when the flanks are grouped and the vernier stands out from the configuration. Here, we show analogous results for color-based grouping. A red vernier flanked by arrays of 10 red lines yielded much higher vernier thresholds than when flanked by arrays of 10 isoluminant green lines and vice versa. Moreover, when a red vernier was flanked by alternating red and green lines, thresholds were even higher than in the condition with only red flanks. We suggest that in the latter configurations the vernier does not stand out from the flanks compared to when all flanks are green. These results add further evidence to the proposition that global rather than local spatial interactions have to be considered in explaining contextual modulation.
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