Association for Behavior Analysis International

Conditional-discrimination procedures offer a powerful experimental framework for examining how antecedent and consequent events control behavior. When conditional stimuli are temporally distant from choice, these procedures allow the investigation of working memory; and when choices are temporally distant from conditional stimuli, delay of reinforcement effects can be addressed. The present symposium explores the complex interplay between control by sample stimuli, immediate and delayed choice stimuli, differential payoff for matching performance, and differential payoff for reporting 1 stimulus class versus another. The papers investigate (1) how differential outcomes following delays to choice result in delay-specific memory (White); (2) the contextual control of matching accuracy and persistence as a function of delay to choice when reinforcer magnitudes differ across contexts (Berry & Odum); and (3) how discriminability and bias between prior colors versus prior response contingencies are controlled by relative reinforcer frequencies (Davison, Podlesnik, & Elliffe). Each of these papers provide data germane to the development of general theories of conditional discrimination and the 3-term contingency.

Remembering over short times is best studied in the delayed matching-to-sample procedure because the 2-alternative choice requirement is amenable to a detection analysis. The procedure is a conditional discrimination in which a successive discrimination between the stimuli to be remembered is combined with the simultaneous discrimination between the choice stimuli. A third element, however, has been somewhat neglected although it is the hallmark of a memory procedure—the retention or delay interval. In the present paper, several experiments are describedthat confirm the importance of the retention interval as a conditional cue. That is, remembering can be delay-specific. These include some new data which suggest that the differential outcomes effect can also be delay-specific. The differential-outcomes effect is manifest as enhanced discriminability at long delays when choice responses are followed by different outcomes such as small versus large rewards. The enhanced discriminability, however, can be countered by strong response bias generated by the differential outcomes. A delay-specific differential-outcomes effect challenges current theories based on the notion of expectancy.

The present experiment was conducted to investigate the effects of reinforcer magnitude on resistance to disruption of remembering and response rates. Pigeons were exposed to a variable-interval (VI) delayed-matching-to-sample procedure (DMTS) with 2 components (rich and lean). Specifically, completion of a VI 20 s multiple schedule resulted in DMTS trials in both components. Four delays (0.1, 4, 8, and 16 s) were introduced between the sample and comparison stimuli, and were presented equally across rich and lean components. The difference between rich and lean components was the length of hopper exposure [either 4.75 s (rich component) or 0.75 s (lean component)] following a correct response. Accuracy and response rates were higher in the rich component relative to the lean during baseline. Following baseline, extinction was introduced, during which initial accuracy decreased more in the lean component relative to the rich component. Response rates also decreased more in the lean relative to rich component. Comparable results were observed using the same VI DMTS preparation with different disruptors.

In the 3-term contingency, can we manipulate selective control by discriminative stimuli versus food reinforcers? Responding on a 2-key concurrent variable-interval schedule under 1 of 2 key colors produced a choice phase in which pigeons were asked about either (1) the color they had just seen in the concurrent phase, or (2) which response they emitted to produce the choice phase. In Condition 1, we varied the relative frequency of asking the 2 questions; in Condition 2, we varied the relative frequency with which left or right responses produced the choice phase; in Condition 3, concurrent-schedule responding produced food prior to the choice phase; and in Condition 4, the food was replaced by a blackout of the same duration. Relative question frequency controlled the discriminability of stimuli required for accurate choice, but relative frequency of payoff for left versus right responding did not control discriminability. The addition of both reinforcers and blackouts following the concurrent phase strongly decreased this control, suggesting that reinforcer-controlled divided attention attenuates rapidly across time.