Drugs and visual perception: Effects of LSD, morphine and chlorpromazine on accuracy, bias and speed

Abstract

Ten pigeons were trained to discriminate between the intensities of two white lights (projected behind a center response “key”) using a discrete trial procedure in which choice behavior involved pecking at red or green lights projected behind left or right side keys. LSD (0.02–0.08 mg/kg) did not alter the accuracy of the brightness discrimination (percent correct) although it did lower response speed and may have differentially affected spatial (position) bias. Morphine (2.5–10.0 mg/kg) decreased accuracy of discrimination as well as response speed and had greater effects on trials when the bright stimulus was presented than when the dim stimulus was presented. Chlorpromazine (7.5–30.0 mg/kg) lowered accuracy without significantly altering any other measure of performance.