D-amphetamine, nicotine, and haloperidol produce similar disruptions in spatial and nonspatial temporal discrimination procedures.

Two different and generally noncomplimentary disruptions of timing by pharmacological agents have been found. One is a lateral shift of the psychophysical curve for time, indicating a subjective shortening or lengthening of time, whereas the other is a flattening of the curve and decrease in temporal accuracy. This study assessed the role of a methodological variation in producing this discrepancy. The procedure used required pigeons to classify stimulus duration intervals as short or long, using response alternatives that were defined either by the location of response keys (spatial), or by their color (nonspatial). D-amphetamine was used to replicate earlier findings, whereas nicotine and haloperidol extended the research to different drug classes. Dose-dependent decreases in the accuracy of classifying temporal intervals and a flattening of the psychophysical curve were found across drug classes for both spatial and nonspatial procedural variations. Procedural variations, under these conditions, could not explain the discrepancy. However, the results from this study added to the mounting body of literature showing decrements in temporal accuracy and a flattening of the psychophysical curve because of a number of diverse pharmacological and nonpharmacological disruptors.