Ward, R. D. & Odum, A. L. (2005).
Effects of morphine on temporal discrimination and color matching: General
disruption of stimulus control or selective effects on timing?
Journal of the Experimental Analysis of Behavior, 84, 401-
415.
Discrepant effects of drugs on behavior maintained by temporal-discrimination
procedures make conclusive statements about the neuropharmacological bases of
timing difficult. The current experiment examined the possible contribution of a
general, drug-induced disruption of stimulus control. Four pigeons responded on
a three-component multiple schedule that included a fixed-interval 2-min,
temporal discrimination, and color-matching component. Under control conditions,
response rates and choice responses during the first two components showed
evidence of control by time, and accuracy for color matching was high in the
third component. Morphine administration flattened the distribution of fixed-
interval responding and produced a general disruption of accuracy in the
temporal-discrimination component, whereas accuracy in the color-matching
component was relatively unaffected. Analysis of the psychophysical functions
from the temporal-discrimination component indicated that morphine decreased
accuracy of temporal discrimination by decreasing overall stimulus control,
rather than by selectively affecting timing. These results suggest the
importance of determining the neurophysiological bases of stimulus control as it
relates to temporal discrimination.
Key words: morphine, timing, stimulus control, temporal discrimination, key
peck, pigeons