Error factors in pigeon discrimination and delayed matching

Pigeons discriminated short from long wavelength stimuli (samples) distributed evenly on a wavelength continuum. Three experiments varied task (left-right or conditional discrimination), sample duration, and sample-choice retention interval. Cumulative normal psychometric functions related choice responses to wavelength. The slope of the functions measured sensitivity to wavelength differences, and their asymptotes measured overall control by the wavelength dimension. Sample duration affected sensitivity in both simple and conditional discriminations. The shift from left-right to conditional discrimination reduced overall stimulus control. Delay between sample and choice affected primarily overall stimulus control. Results suggest that stimulus duration mainly affects stimulus processing, whereas changes in the sample-choice retention interval may mainly affect the retention of a prospective code.