For our final example of how the combination of multiple measures can inspire theoretical advances that would otherwise be purely speculative, consider the general problem of how to purify a measure of memory so that our assessment is minimally confounded by factors that look like remembering, but are in fact simply nondeliberative influences of memory. For example, consider a memory experiment in which subjects learn semantically or asso-ciatively related pairs of words such as bread-butter or wishing-well. If we test later memory by presenting the first term of each pair and attempting to elicit the second (bread-?), it is an impossible task to discern whether a response of butter reveals mnemonic retrieval of the previous study episode or simply temporary enhanced access to that word by virtue of automatic effects and influences of memory. Even more dastardly, the response might indicate nothing more than the prelearned nature of the association—through a lapse in attention or perhaps strategic yawning, the subject may have never even seen the study pair. How can we tease out the deliberative recollective aspect of memory in such a data set?
Jacoby (1991) provided a clever solution to this problem that involves the use of multiple measures. In his experiments, subjects provided their responses under two different conditions. The first replicated the typical memory experiment, in which they were told simply to remember the target word if possible and report it. In the other condition, subjects were told explicitly to produce any word except the target word. The combination of these conditions allowed Jacoby (1991) to specify a theory of how deliberate and automatic influences of memory interact to produce responses in this type of cued recall paradigm. He claimed that, in the standard (henceforth, inclusion) condition, a response that matched the prior study item could reflect either form of memory and assumed that their contributions were independent of one another:
Here R indicates the probability of correct recollection of the study episode, and A indicates the probability of automatic nonrecollective influences leading to a correct response. In the condition in which subjects are told not to produce the previously studied pair word, the sources combine differently:
That is, if the target word were to be recollected, it would not be produced. Thus, a target response in this condition indicates a lack of such recollection. Under such conditions, the target might nonetheless be produced if automatic influences of memory lead that word to be particularly accessible. The difference between performance in these two conditions is thus equal to R and provides a modelbased estimate of the recollective memory contribution to performance in the task. Given this estimate, it is easy to derive the estimate for the parameter A, which reflects the automatic nonrecollective memory influence on the task.
In one striking example of how the combination of inclusion and exclusion memory tasks yields results that would otherwise be unobtainable, consider an experiment reported by Jacoby, Toth, and Yonelinas (1993). Subjects were exposed to two lists of words, the first of which subjects were told to remember and was presented aurally. The second list was presented visually, and subjects were told to read the words aloud. During this second list, some subjects performed an additional attention-dividing task and others did not. The final recall test consisted of presenting word stems (e.g., mer—) and, in the inclusion condition, asking subjects to recall a word from either list that completed that cue; in the exclusion condition, they were instructed to specifically avoid completing the cue with a word that had been presented in either earlier study list. Table 24.1 shows the raw data for the inclusion and
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