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.
Keywords: attention, eye-movements, color
Citation: Frey H-P, Wirz K, Willenbockel V, Betz T, Schreiber C, Troscianko T and König P (2011) Beyond correlation: do color features influence attention in rainforest? Front. Hum. Neurosci. 5:36. doi: 10.3389/fnhum.2011.00036
Received: 07 December 2010;
Accepted: 24 March 2011;
Published online: 08 April 2011.
Edited by:Leon Y. Deouell, The Hebrew University of Jerusalem, Israel
Reviewed by:Tom Foulsham, University of Essex, UK
Copyright: © 2011 Frey, Wirz, Willenbockel, Betz, Schreiber, Troscianko and König. This is an open-access article subject to a non-exclusive license between the authors and Frontiers Media SA, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and other Frontiers conditions are complied with.
*Correspondence: Hans-Peter Frey, Department of Pediatrics, Albert Einstein College of Medicine, 1225 Morris Park Avenue, Bronx, NY 10461, USA. e-mail: firstname.lastname@example.org