@ARTICLE{10.3389/fnhum.2011.00036, AUTHOR={Frey, Hans-Peter and Wirz, Kerstin and Willenbockel, Verena and Betz, Torsten and Schreiber, Cornell and Troscianko, Tomasz and Konig, Peter}, TITLE={Beyond Correlation: Do Color Features Influence Attention in Rainforest?}, JOURNAL={Frontiers in Human Neuroscience}, VOLUME={5}, YEAR={2011}, URL={https://www.frontiersin.org/articles/10.3389/fnhum.2011.00036}, DOI={10.3389/fnhum.2011.00036}, ISSN={1662-5161}, 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.} }