Within‐session Analysis of Visual Discrimination

Within‐session changes in responding by pigeons during a maintained successive discrimination procedure were examined in four experiments. In the first two experiments, which involved discrimination of visual flicker rate, within‐session changes in responding were minimal or absent. A third experiment, which examined discrimination of rectangular forms, demonstrated that the absence of within‐session changes in responding was not limited to flicker‐rate stimuli. A fourth experiment showed that the absence of within‐session changes in responding was not due to high task difficulty in the previous experiments. For the group of subjects in each experiment, within‐session changes in responding did not influence discrimination performance. Therefore, measures of overall response rate accurately represented responding both within and across sessions. The occasional appearance of within‐session decreases in responding for a few birds may be attributable to satiation.