Discrimination of oriented visual textures by poultry chicks.

We investigated how poultry chicks discriminate textures of lines sharing a common orientation from textures of variably oriented lines. Stimulus colours along with illumination were adjusted to selectively stimulate different receptor mechanisms. Chicks could discriminate achromatic textures, but not textures isoluminant to the double cones that gave a long vs. medium wavelength chromatic signal, nor an intensity signal for the short and very-short wavelength cones. These results suggest that detection of line orientation and texture discrimination uses an achromatic signal derived either from the double cones, or summed outputs of long and medium wavelength sensitive single cones.