Academic journal article Memory & Cognition

Recency and Primacy in Causal Judgments: Effects of Probe Question and Context Switch on Latent Inhibition and Extinction

Academic journal article Memory & Cognition

Recency and Primacy in Causal Judgments: Effects of Probe Question and Context Switch on Latent Inhibition and Extinction

Article excerpt

Traditional associative models assume that associative weights are updated on a trial-by-trial basis. As a result, it is usually expected that responses based on these weights will tend to reflect the most recently presented contingencies. However, a number of studies of human causal judgments have shown primacy effects, wherein judgments obtained at the end of a series of trials are more strongly influenced by a contingency that was in force early in the sequence than by a contingency that was in force later in the sequence. The experiments described in this article replicated other work showing that requesting causal judgments during a sequence can reverse primacy and produce strong recency effects. Evidence was also obtained to suggest that primacy effects are produced by an interaction between latent inhibition and extinction processes and that requesting a judgment affects both of these processes.

Associative theories (e.g., the Rescorla-Wagner model) suggest that causal judgments are based on the strength of an associative link between a mental representation of the cause and a mental representation of the effect (Rescorla & Wagner, 1972). This associative link is updated on a trial-by-trial basis, so judgments should tend to reflect the most recently experienced contingency. As a result, if participants experience a positive followed by a negative contingency between a putative cause and an effect, they should judge a cue as less of a cause than if they have experienced a negative followed by a positive contingency between the cause and the effect.

However, exactly the opposite result has been found in a number of experiments. Instead of finding recency effects, some investigators have found primacy effects. For example, Dennis and Ahn (2001) carried out a study in which they presented participants with a series of trials. On each trial, the participants were given information on whether consumption of an exotic plant produced a physical reaction. After the trial series, the participants then had to judge the extent to which the plant was a cause of the reaction. Over the entire trial series, the overall contingency between consumption and reaction was zero, as measured using Äp (Allan, 1980). Experimental conditions were created such that, within the context of this zero contingency, the participants experienced confirmatory trials predominantly in the first half of the series (a CF series) or predominantly in the second half of the series (a CS series). Confirmatory trials were defined as Cells A and D from the standard 2 × 2 contingency table, whereas disconfirmatory trials were defined as Cells B and C.

Cell A and Cell D trials are those on which the putative cause is present along with the effect and those on which both the cause and the effect are absent, respectively. Cell B and Cell C trials are those on which the cause is present and the effect is absent and those on which the cause is absent and the effect is present, respectively. It might be expected under these two conditions that judgments would be equivalent, as suggested by Äp, or that there would be a recency effect, reflecting a trial-by-trial updating process with higher ratings given following a CS series. In fact, a primacy effect was observed. Higher ratings were given following a CF series.

Using a similar design, Collins and Shanks (2002) found either that the order of confirmatory and disconfirmatory information made no difference (Experiments 3 and 4) or that a primacy effect was observed (Experiment 2). In addition, Collins and Shanks found recency effects, so that a contingency was judged as more causal following a CS series. This recency effect was found when causal judgments were made more frequently (after every block of 10 trials) than when they were made once, at the end of the trial series. Other investigators have also reported an effect of judgment frequency (Catena, Maldonado, & Cándido, 1998; Catena, Maldonado, Megías, & Frese, 2002; Matute, Vegas, & De Marez, 2002), and Catena et al. …

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