Color induction in equiluminant flashed stimuli

Abstract

Color induction is the influence of the surrounding color (inducer) on the perceived color of a central region. There are two different types of color induction: color contrast (the color of the central region shifts away from that of the inducer) and color assimilation (the color shifts towards the color of the inducer). Several studies on these effects used uniform and striped surrounds, reporting color contrast and color assimilation, respectively. Other authors (Kaneko and Murakami, J Vision, 2012) studied color induction using flashed uniform surrounds, reporting that the contrast was higher for shorter flash duration. Extending their work, we present new psychophysical results using both flashed and static (i.e., non-flashed) equiluminant stimuli for both striped and uniform surround. Similarly to them, for uniform surround stimuli we observed color contrast, but we did not obtain the maximum contrast for the shortest (10 ms) flashed stimuli, but for 40 ms. We only observed this maximum contrast for red, green and lime inducers, while for a purple inducer we obtained an asymptotic profile along flash duration. For striped stimuli, we observed color assimilation only for the static (infinite flash duration) red-green surround inducers (red 1st inducer, green 2nd inducer). For the other inducers' configurations, we observed color contrast or no induction. Since other works showed that non-equiluminant striped static stimuli induce color assimilation, our results also suggest that luminance differences could be a key factor to induce it.

The contribution of luminance and chromatic channels to color assimilation

“…In agreement with previous studies ( Fach & Sharpe, 1986 ; Cerda-Company et al., 2018 ; Cerda-Company & Otazu, 2019 ), we observed that color induction along the two chromatic axes depends on both the chromatic and luminance conditions. This observation is supported by the best fitted linear model: ColorInduction l,s ConditionL * ConditionS * ConditionY + (1 Participant).…”

Chromatic Induction in Migraine

“…Moreover, Condition 4 causes a stronger assimilation in the s axis than Condition 2. The dependency between chromatic induction and chromaticity of the inducers we observed is in line with previous studies in which we concluded that colour assimilation does not only depend on the differences in luminance between inducers but also on the chromaticity of the inducers [12,50].…”

“…As the l and s axes of the MacLeod-Boynton colour space are not perceptually comparable, to compare the strength of colour induction among the different stimulus configurations we used a metric for colour induction defined in [12,50] that treats the two axes separately. For each axis i, where i = [l, s], we computed the ratio of the difference between the output of the experiment, i.e., the chosen, or 'perceived', colour, C c i , and the test colour C t i , and the difference between the colour of the (first) inducer C s i and the test colour C t i , as…”

“…We estimated this region (∆E = 1) from the CIELab colour space as this space is approximately perceptually uniform. We then transformed this estimate to the MacLeod-Boynton colour space and to the metric units afterwards (see [12]).…”

“…The activity of a neuron responding to colour in a central region can therefore be modified through contextual influences by the colour of neighbouring areas outside its classical receptive field, resulting in chromatic induction [5,6]. Computational models based on centre-surround mechanisms, or mimicking the excitatory-inhibitory networks responsible for contextual influences in the primary visual cortex, reproduce induction effects quantitatively [4,11,12] and qualitatively [13].…”