Effects of sodium pentabarbital on matching behavior in the pigeon.

Nine pigeons in a matching-to-sample task with 5 alternative stimuli were exposed to 4 dose levels of sodium pentobarbital. Each drug session alternated with a control session, and 6 determinations were made at each dose level. Dose-response curves were obtained, and drug effects are described for position-specific and stimulus-specific behaviors. These results suggest that the drug effect is to weaken control by the sample stimulus and shift control to properties of the comparison stimuli.