For polarization tuning curves (Appendix 1–figure 1A), we used the responses of pixels in the region of ‘neurons’ in each animal (see Polarization-selectivity index). For each pixel, we calculated the average fluorescence intensity (Fm) at each angle of polarization presented and normalized values by calculating ΔF/F = Fm/F0-1, where F0 was the average intensity during periods of inactivity between stimulus sets. We interpolated each pixel’s resulting tuning curve in the Fourier domain, resampling to 360 data points, then shifted the curve according to the pixel’s preferred angle of polarization (rounded to the closest degree) so that all tuning curves were aligned. We then found the average tuning curve for all pixels in each individual animal.