STEREOSCOPIC DEPTH-PERCEPTION IN THE OWL

IT is unclear whether the neural algorithm that underlies stereoscopic vision in birds incorporates both low level (camouflage breaking) and high level (depth ordering) comparisons of information available to e ach of the eyes. Both visual functions were successfully tested by exa mining transitive inference performance in two barn owls trained to di scriminate static Julesz random dot stereograms, thus demonstrating a capacity to detect relative depth using fine retinal disparity as the sole cue for discrimination. Our behavioral tests provide strong evide nce that the barn owl possesses global stereopsis comparable to that f ound in the macaque monkey - the owl's best stereoacuity was 2 min of are. (C) 1998 Rapid Science Ltd.