Academic journal article Memory & Cognition

Trial Order and Retention Interval in Human Predictive Judgment

Academic journal article Memory & Cognition

Trial Order and Retention Interval in Human Predictive Judgment

Article excerpt

The influences of order of trial type and retention interval on human predictive judgments were assessed for a cue that was reinforced on half of its training presentations. Subjects observed 10 cue-outcome presentations (i.e., reinforced trials) and 10 cue-alone presentations (i.e., nonreinforced trials) in one of three different orders: all nonreinforced trials followed by all reinforced trials (latent inhibition), reinforced and nonreinforced trials interspersed (partial reinforcement), or all reinforced trials followed by all nonreinforced trials (extinction). Ratings were based mainly on the most recent event type (i.e., a recency effect) when the test occurred immediately after training but were based mainly on initial event types (i.e., a primacy effect) when the test occurred after a 48-h delay. The subjects tested both immediately and with a long retention interval did not exhibit this shift to primacy (i.e., the recency effect persisted). These results demonstrate noncatastrophic forgetting and the flexible use of trial order information in predictive judgments.

Of all the cognitive tasks that animals, including humans, perform, surely few are more important than the ability to predict future events on the basis of past events. Throughout much of the 20th century, the systematic study of this type of simple inference was concentrated among investigators of Pavlovian conditioning (Pavlov, 1927). In Pavlovian conditioning, subjects are exposed to an initially neutral conditioned stimulus (CS; e.g., a light), followed by an unconditioned stimulus (US; e.g., an electric shock). With repeated pairings of the two (light and shock), subjects come to display conditioned responses to the light that are anticipatory in nature (e.g., freezing in response to the light). Phrased more cognitively, with repeated CS-US pairings, subjects increasingly behave as if they expect the US to recur when the CS is presented on a test trial. Investigators in this area have identified a large number of basic variables that control how rapidly and to what level this anticipatory behavior develops (for summaries of the controlling variables of Pavlovian conditioning, see Hearst, 1988; Miller & Escobar, 2002).

Reviving an older line of work by Jenkins and Ward (1965), since the 1980s, many cognitive psychologists have studied analogous tasks involving human subjects in which the "conditioned response" is a verbally expressed judgment of the likelihood that an outcome will again follow a cue with which it has been accompanied during past trials. For example, subjects might diagnose the likelihood that a patient will develop an allergy after having consumed some food that was paired or not paired with allergies in the past (Allan, 1993). An interesting finding of studies of this type has been the large extent to which human predictive judgments are affected by the same variables that affect nonhuman animals' conditioned responses, particularly in competition between multiple predictor cues for control over behavior (for reviews, see Allan, 1993; Shanks, Holyoak, & Medin, 1996). Given their operational similarity, the conclusion that these preparations obey similar principles is not surprising (Allan, 1993; Dickinson, Shanks, & Evenden, 1984; Gluck & Bower, 1988; Shanks & Dickinson, 1987). In fact, the similarities are so many in number that several investigators within the field routinely use associative and nonassociative models originally developed to explain Pavlovian conditioning to explain human predictive and causal judgments. However, largely because the study of predictive judgment is younger than the study of Pavlovian conditioning, the potential influence of many basic variables known to influence Pavlovian conditioning and, thus, the soundness of correspondence between these two types of inference remains to be fully explored.

One variable that has received recent attention in both areas is trial order. …

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