Intertrial sources of stimulus control and delayed matching-to-sample performance in humans.
Two experiments compared delayed matching-to-sample (DMTS) accuracy under 2 procedures in adults with mental retardation. In the trial-unique procedure, every trial in a session contained different stimuli. Thus, comparison stimuli that were correct on one trial were never incorrect on other trials in that session (or vice versa). In the 2-sample DMTS procedure, the same 2 comparison stimuli were presented on each trial, and their function changed quasi-randomly across trials conditional upon the sample stimulus. Across 2 experiments, 7 of 8 subjects showed the highest overall accuracy under the trial-unique procedure, and no subject showed consistently higher accuracy under the 2-sample procedure. Negative, exponential decay functions fit to logit p values showed that this difference was due largely to the steeper delay-mediated decline in sample control for the 2-sample procedure. Stimulus-control analyses indicated that, under the 2-sample procedure, the selection of the comparison stimulus on Trial N was often controlled by the comparison stimulus selection on Trial N-1 rather than the Trial-N sample stimulus. This source of competing stimulus control is not present in trial-unique procedures. Experiment 2 manipulated intertrial interval duration. There was a small but consistent increase in accuracy as a function of intertrial interval duration under the 2-sample procedure, but not under the trial-unique procedure.
Williams
Dean C
DC
Parsons Research Center, University of Kansas, Parsons 67357, USA. Deanwms@ku.edu
Johnston
Mark D
MD
Saunders
Kathryn J
KJ
D000328:Adult; D001288:Attention; D003220:Conflict, Psychological; D004193:Discrimination Learning; D005260:Female; D006801:Humans; D008607:Intellectual Disability / Q000523:psychology*; D008297:Male; D008570:Memory, Short-Term; D009949:Orientation; D010364:Pattern Recognition, Visual; D011597:Psychomotor Performance; D012055:Reinforcement Schedule; D013998:Time Perception