The acquisition of trace supraordinate stimulus control in pigeons

Abstract

Match-to-sample and oddity-from-sample problems with four colors were acquired by two pigeons under the supraordinate control of a line tilt superimposed on samples. Since the supraordinate stimulus terminated before the comparison stimuli were presented, accurate matching and oddity performance indicated trace stimulus control as well. The temporal extent of trace control was assessed in one subject by presenting probes-trials without a line tilt on the sample-in which the basis of correct responding was the supraordinate stimulus presented on the previous trial. Trace supraordinate control did not extend between trials. Subsequently, the delay between the termination of the supraordinate stimulus and the presentation of the comparison stimuli was gradually increased within a trial. Both subjects were able to perform matching and oddity over longer delays, and eventually on probe trials, although accuracy decreased. Results were discussed in terms of instructional stimulus control and memory. Instructional stimuli have two general properties:(1) to control responding over a range of discrimination problems, that is, to exert supraordinate control (Reynolds, 1968) and (2) to continue to exert control beyond the stimulus duration, which is called trace control. Stimuli in match-to-sample and oddity-fromsample procedures combine elements of both properties and permit the investigation of instructional stimulus control (Cumming & Berryman, 1961).Supraordinate control or higher order conditional stimulus control (Nevin, 1973) deals with classes of stimulus-response relationships. Matching can serve as a class of stimulus-response relationships, indicating supraordinate control over a range of problems, e.g., matching colors. Supraordinate stimulus control was studied by Nevin and Liebold (1966), who trained pigeons to perform match-to-sample using red and green stimuli when a yellow light above the response keys was illuminated and to perform oddity-from-sample when it was off. The yellow light exerted supraordinate control over problems when the center key was either red or green. If a stimulus terminates before the opportunity to respond, then the procedure involves trace stimulus control. Delayed match-to-sample (Blough, 1959) examines the trace aspect of the sample's control by delaying the onset of the comparison stimuli until after the termination of the sample. If the sample continues to exert control beyond its duration, then trace stimulus control is indicated.The present study investigated the acquisition of instructional stimulus control in pigeons. This was accomplished by establishing a supraordinate stimulus dimension that controlled matching and oddity but which was not present during the choice of comparison (O-see delay). An attempt was made to modify the extent of the trace control by titrating the delay interval between the offset of the supraordinate stimulus and the opportunity to respond to the comparison stimuli. Further, if the trace aspect of instructional control extended beyond one trial, i...