Conditioned reinforcement of human observing behavior by descriptive and arbitrary verbal stimuli.
College students earned monetary reinforcers by pressing a key according to a compound schedule with variable-interval and extinction components. Pressing additional keys occasionally produced displays of either of two verbal stimuli; one was uncorrelated with the schedule components, and the other was correlated with the extinction component. In Experiments 1 and 2, the display area of the apparatus was blank unless an observing key was pressed, whereupon a descriptive message appeared. Most students preferred an uncorrelated stimulus stating that "Some of this time scores are TWICE AS LIKELY as normal, and some of this time NO SCORES can be earned" over a stimulus stating that "At this time NO SCORES can be earned." In Experiment 3, the display area indicated that "The Current Status of the Program is: NOT SHOWN." Presses on the observing keys replaced this message with stimuli that provided arbitrary labels for the schedule conditions. All of the students preferred a stimulus stating that "The Current Status of the Program is: B" over an uncorrelated stimulus stating that "The Current Status of the Program is: either A or B." Thus, under some circumstances, observing was maintained by a stimulus correlated with extinction-a finding that poses a challenge for Pavolvian accounts of conditioned reinforcement. Differences in the maintenance of observing by the descriptive and arbitrary stimuli may be attributed to differences in either the strength or nature of the instructional control exerted by the verbal stimuli.