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Declan McKeefry, Mark Burton, Neil Parry; The perceived speed of chromatic and luminance gratings in the presence of adjacent modifier stimuli. Journal of Vision 2005;5(12):74. doi: 10.1167/5.12.74.
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© ARVO (1962-2015); The Authors (2016-present)
We have examined the extent of interaction between colour and luminance contrast in human speed perception. Employing a ‘modifier speed matching’ paradigm (Smith & Derrington, 1996), we measured the perceived speed of moving luminance (L+M) and chromatic (both red-green (L−M) and blue-yellow S-(L+M)) sinusoidal grating test stimuli in comparison to a reference stimulus with a constant speed of 3 deg/sec. The speed matches were made in the presence of high contrast modifier stimuli which flanked either side of the test stimulus and comprised either luminance or chromatic gratings which varied in terms of their speed. The modifiers, regardless of whether they were chromatically- or luminance-defined, were found to have an effect on the perceived speed of all test stimuli. The presence of a modifier slower than the reference speed (< 3 deg/sec), decreased the perceived speed of the test stimulus, whilst in the presence of a faster modifier (> 3 deg/sec) the perceived speed was increased. The results indicate that the perception of speed of luminance and chromatic gratings is not analysed within independent pathways at low stimulus speeds, but computed across sampling areas within which there is pooling of chromatic and luminance contrast information.
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