Abstract
Background. For surface color to be useful for object identification, the surface color must be estimated from the incoming light signal and then compared to a memory representation of the object being identified. Color constancy and color memory have been extensively studied individually, but their relationship has rarely been addressed. Here we investigate the relationship between color constancy and color memory by separately and jointly measuring the effects of chromatic context and delay on hue matches. Methods. 8 observers compared the hue of two briefly presented 2-degree patches in a 2AFC experiment. Three reference patches (yellow-green, green, blue-green) were employed. Patches were presented: 1) with a 2 second inter-stimulus interval on a uniform surround (memory condition); 2) simultaneously with a hue difference between the reference and test surrounds (constancy condition); or 3) with both the delay and the surround difference (combined condition). We fit psychometric functions to the proportion-bluer data in each condition and estimated the bias (the point of subjective equality). The independence of color perception and memory was assessed by quantifying the degree of additivity in the combined matches. Results. The surround expectedly caused a hue bias in the constancy condition. More surprisingly, the delayed hue matches in the memory condition were also systematically biased. A control experiment with multiple stimulus ranges suggested that this was due to a central tendency bias. In the combined condition, the bias for all observers was around half that expected from linear addition of the memory and constancy biases, showing significant subadditivity of constancy and memory. A Bayesian model incorporating increasing noise during the delay and a prior set by the stimulus range accounted for both biases. Conclusion. The delay bias and the subadditivity suggest interactions between perceptual and short-term memory processes that can be parsimoniously accounted for within a Bayesian framework.
Meeting abstract presented at VSS 2013