Addresses for correspondence:

Object orientation and visual search 2 Four experiments investigated the influence of canonical orientation on visual search for objects. Search displays were composed of pictures of animals whose main axis of elongation was either vertical or tilted when presented in their canonical orientation. The orientation of a target object could be either congruent or incongruent with its canonical orientation. In Experiment 1 vertical canonical targets were detected faster when they were presented in a tilted orientation (incongruent with their canonical orientation) than in a vertical orientation (congruent with canonical orientation). However, this search asymmetry was reversed for tilted canonical objects, i.e., search was faster for vertical than for tilted targets. In Experiment 2, this effect of congruency with canonical orientation was partially preserved when the search elements were high-pass filtered, but it was eliminated when the objects were low-pass filtered, rendering them as unfamiliar shapes. Inverting the elements also eliminated the effect of canonical orientation, and produced a search asymmetry as a function of physical orientation (Experiment 3). Finally, the effect of canonical orientatio