Effects of stimulus dimension and of trial and intertrial illumination on acquisition of a match/mismatch task by pigeons

Birds were trained on a higher order conditional discrimination task, one that required birds to match samples and comparisons on some trials and to mismatch on other trials. Which task component was in effect was indicated by the level of chamber illumination (houselight-on and houselight-off instructions). Acquisition of the components of a color (red and green) match/mismatch task in the first half of the experiment was not differentially affected by the level of illumination associated with each task component, by houselight changes per se, or by the level of illumination during the intertriai interval (ITI). However, when shapes (plus and circle) were used to train the task in the second half of the experiment, performance on the houselight-cued task component exceeded performance on the dark-cued task component, and ITI illumination facilitated performance on both task components. These results suggest that attention to shape stimuli, but not to colors, may vary systematically as a function of chamber illumination level.