Many crustaceans are sensitive to the polarization of light and use this information for object-based visually guided behaviours. For such tasks, we do not know whether polarization and intensity information are integrated into a single-contrast channel, whereby polarization directly contributes to perceived intensity, or whether polarization and intensity are processed separately and in parallel. Using a novel type of visual display technology that allowed polarization and intensity properties of visual stimuli to be adjusted independently and simultaneously, we conducted behavioural experiments with fiddler crabs to test which of these two models of visual processing are used. We discovered that, for a loom detection task, fiddler crabs process polarization and intensity information independently and in parallel. The crab’s response depended on whatever contrast was the most salient. By contributing independent measures of visual contrast, intensity and polarization provide a greater range of detectable contrast information for the receiver, increasing the chance of detecting a potential threat.
Smithers, S. P., Roberts, N. W., & How, M. J. (2019). Parallel processing of polarization and intensity information in fiddler crab vision. Science Advances, 5(8), [eaax3572]. https://doi.org/10.1126/sciadv.aax3572