Optomotor trials examining sensitivity of Premnas biaculeatus to linearly polarized light.

The proportion of positive optomotor responses (N = 59) to the control, polarized stripes and black-and-white stripes patterns (W, POL and BW; respectively), with different options of considering borderline cases (in which it was hard to decide whether the response was positive or negative). Ratios of fish responding with actual numbers are given in parenthesis. Chi-squared and p-values pertain to a test for the equality of proportions (proportions test); testing the null hypothesis that the probability of responding positively to POL is equal to the expected by chance (W).