A recent study by Yeh, Xing, and Shapley over at The Center for Neural Science, New York University made a fascinating discovery about the primary visual cortex of the macaque monkey and it's preference for black over white stimuli similar to that of humans. Here's a snippet from their abstract.
From recordings of single-cell activity in the macaque monkey's primary visual cortex (V1), we found that black-dominant neurons substantially outnumbered white-dominant neurons in the corticocortical output layers 2/3, but the numbers of black- and white-dominant neurons were nearly equal in the thalamocortical input layer 4c. These results strongly suggest that the black-over-white preference is generated or greatly amplified in V1. The predominance of OFF neurons in layers 2/3 of V1, which provide visual input to higher cortical areas, may explain why human subjects detect black more easily than white. Furthermore, our results agree with human EEG and fMRI findings that V1 responses to decrements are stronger than to increments, though the OFF/ON imbalance we found in layers 2/3 of macaque V1 is much larger than in the whole V1 population in the human V1 experiments (Zemon et al., 1988, 1995; Olman et al., 2008).No wonder boldface text literally catches the eye.
Yeh CI, Xing D, & Shapley RM (2009). "Black" responses dominate macaque primary visual cortex v1. The Journal of neuroscience : the official journal of the Society for Neuroscience, 29 (38), 11753-60 PMID: 19776262