title: Beyond correlation: do color features influence attention in rainforest?
abstract: Recent research indicates a direct relationship between low-level color features and visual attention under natural conditions. However, the design of these studies allows only correlational observations and no inference about mechanisms. Here we go a step further to examine the nature of the influence of color features on overt attention in an environment in which trichromatic color vision is advantageous. We recorded eye-movements of color-normal and deuteranope human participants freely viewing original and modified rainforest images. Eliminating red-green color information dramatically alters fixation behavior in color-normal participants. Changes in feature correlations and variability over subjects and conditions provide evidence for a causal effect of red-green color-contrast. The effects of blue-yellow contrast are much smaller. However, globally rotating hue in color space in these images reveals a mechanism analyzing color-contrast invariant of a specific axis in color space. Surprisingly, in deuteranope participants we find significantly elevated red-green contrast at fixation points, comparable to color-normal participants. Temporal analysis indicates that this is due to compensatory mechanisms acting on a slower time scale. Taken together, our results suggest that under natural conditions red-green color information contributes to overt attention at a low-level (bottom-up). Nevertheless, the results of the image modifications and deuteranope participants indicate that evaluation of color information is done in a hue-invariant fashion.
authors.affiliation: Department of Neurobiopsychology, Institute of Cognitive Science, University of Osnabrück Osnabrück, Germany.
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Frey
authors.forename: Kerstin
authors.initials: K
authors.lastname: Wirz
authors.forename: Verena
authors.initials: V
authors.lastname: Willenbockel
authors.forename: Torsten
authors.initials: T
authors.lastname: Betz
authors.forename: Cornell
authors.initials: C
authors.lastname: Schreiber
authors.forename: Tomasz
authors.initials: T
authors.lastname: Troscianko
authors.forename: Peter
authors.initials: P
authors.lastname: König