RANGE EFFECTS USING INSTRUMENTAL CHOICE PROCEDURES

Pigeons were trained to discriminate visual flicker-rate stimuli using two types of instrumental choice procedures. One experiment used a fr ee-operant concurrent schedule with multiple schedule components. Two additional experiments used a two-alternative, discrete-trial procedur e. In all experiments, the range of training stimuli was manipulated a cross conditions. Results from all three experiments showed typical ra nge effects on discrimination performance. That is, performance declin ed with increases in the overall range of variation of training stimul i. These range effects occurred with either continuous response rate m easures or discrete choice measures. Moreover, range effects appeared with relatively high or low levels of overall discrimination accuracy and with either symmetrical or asymmetrical extensions of stimulus ran ge. The results of these experiments suggest that increasing stimulus range influences both perceptual sensitivity and bias to response alte rnatives.