Neil W. Mulligan

The Role of Attention During Encoding in Implicit and Explicit Memory

In 5 experiments, participants read study words under conditions of divided or full attention. Dividing attention reduced performance on the general knowledge test, a conceptual implicit test of memory. Likewise, dividing attention reduced conceptual priming on the word--association task, as well as on a matched explicit test, associate-cued recall. In contrast, even very strong division of attention did not reduce perceptual priming on word-fragment completion, although it did reduce recall on the matched explicit test of word-fragment-cued recall. Finally, dividing attention reduced recall on the perceptual explicit tests of graphemic-cued recall and graphemic recognition. The results indicate that perceptual implicit tests rely minimally on attention-demanding encoding processes relative to other types of memory tests. The obtained pattern of dissociations is not readily accommodated by the transfer-appropriate-processing (TAP) account of implicit and explicit memory. Potential extensions of the TAP view are discussed.

Divided attention and indirect memory tests

Attentional state during acquisition is an important determinant of performance on direct memory tests. In two experiments we investigated the effects of dividing attention during acquisition on conceptually driven and data-driven indirect memory tests. Subjects read a list of words with or without distraction. Memory for the words was later tested with an indirect memory test or a direct memory test that differed only in task instructions. In Experiment 1, the indirect test was categoryexemplar production (a conceptually driven task) and the direct test was category-cued recall. In Experiment 2, the indirect test was word-fragment completion (a data-driven task) and the direct test was word-fragment cued recall. Dividing attention at encoding decreased performance on both direct memory tests. Of the indirect tests, category-exemplar production but not word-fragment completion was affected. The results indicate that conceptually driven indirect memory tests, like direct memory tests, are affected by divided attention, whereas data-driven indirect tests are not. These results are interpreted within the transfer-appropriate processing framework.

Generation and hypermnesia.

The multifactor account of the generation effect makes detailed predictions about the effects of generation on item-specific and relational encoding, predictions confirmed in four experiments using a multiple-test methodology. In pure-list designs with unrelated study items, generation produced more interest item gains (indexing greater item-specific processing) and more interest item losses (indexing less relational processing) relative to the read condition. In a mixed-list design, generation produced more gains but did not affect losses. With categorically-related study items, generation produced more gains but fewer losses (indicating enhanced relational encoding). Generation consistently produced hypermnesia whereas reading did so only for related study items. Also, a significant generation effect emerged on later tests under conditions (between-subjects design, unrelated study items) which typically yield no generation effect.

The Effects of Perceptual Interference at Encoding on Organization and Order: Investigating the Roles of Item-Specific and Relational Information

Interfering with the perceptual processing of a stimulus can improve memory. The perceptual-interference effect was investigated from the perspective of the item-specific/relational encoding distinction. This perspective suggests that perceptual interference enhances item-specific encoding but disrupts the encoding of relational and order information. The results of 6 experiments were largely consistent with this view. In Experiments 1 and 2, perceptual interference (a hypothesized item-specific manipulation) and list organization (a relational manipulation) both enhanced free recall but had opposite effects on a measure of relational processing (category clustering). Increasing list organization increased clustering, whereas perceptual interference decreased clustering. In addition, perceptual interference typically decreased memory for order. Finally, when order information was an important determinant of free recall, the perceptual-interference effect was eliminated or reversed. When reliance on order information was lessened, the perceptual-interference effect reemerged.

Self-Generation and Memory

Publisher Summary This chapter focuses on the limiting conditions of self-generation and the theoretical accounts that these limitations have shaped. Extant theoretical accounts of generation imply an encoding trade-off, in which generation enhances item-specific processing at a cost to the encoding of inter item relations, order memory, and contextual associations. The chapter examines the effects of self-generation on memory as exemplified by the generation manipulation and the related perceptual interference manipulation. It begins by introducing the traditional view that self-generative encoding is advantageous. Although the chapter emphasizes null and negative effects of generation because of their theoretical import, it should not neglect to mention the substantial evidence in favor of this traditional view. Indeed, the positive effects of generation and perceptual interference on tests of item memory (such as recognition) are pervasive, typically large and nearly uniform across studies. In this regard, generative encoding certainly enhances memory. In sum, the trade-off accounts are a useful corrective to the traditional belief that self-generative encoding necessarily or generally enhances memory. These accounts have provided theoretical reasons for observed limitations of the generation effect and pointed in the direction of new limitations.

Inhibition and attention deficit hyperactivity disorder in adults

The inhibitory account of attention deficit hyperactivity disorder (ADHD) was tested by examining the performance of college-aged adults on a variety of inhibitory tasks. The poorer performance of adults with ADHD compared with controls on negative priming, stopping, and continuous performance tasks, combined with similar group performances on a test of working memory capacity, indicates a specific inhibitory deficit as opposed to a general limitation in attentional capacity. Overall results provide evidence for extending the inhibitory deficit hypothesis to adult ADHD, not only for mechanisms of response (or motor) inhibition but also for mechanisms of cognitive inhibition.

THE EFFECTS OF PERCEPTUAL INTERFERENCE AT ENCODING ON IMPLICIT MEMORY, EXPLICIT MEMORY, AND MEMORY FOR SOURCE

Interfering with stimulus identification can enhance later explicit memory performance. This counterintuitive (and theoretically unexpected) phenomenon was investigated in 5 experiments. Perceptual interference enhanced category-cued recall (a conceptually driven explicit test) but had no effect on a comparable implicit memory test, category-exemplar production. This dissociation was obtained across higher levels of priming and with high-frequency as well as low-frequency exemplars. Furthermore, although perceptual interference enhanced old-new recognition memory, it did not enhance rhyme recognition (a data-driven explicit test) or source discriminability. Explanations based on enhanced semantic elaboration or enhanced encoding of spatio-temporal context do not account for the perceptual-interference effect. An account based on compensatory processing of higher level perceptual representations remains viable and is discussed in terms of the transfer-appropriate processing framework and the item-specific-relational distinction.

Perceptual interference improves explicit memory but does not enhance data-driven processing

Nairne (1988) has recently demonstrated that interfering with the perceptual processing of an item at study improves later memory for that item. Nairne hypothesized that interfering with perceptual processes induces a data-driven generation process that enhances the representation of visual information. Using a variant of Nairnes procedure, we both replicated his original findings and tested his hypothesis that enhanced data-driven processing causes the current effect. The results of studies using free recall and perceptual identification tests were inconsistent with Nairnes hypothesis. We consider several alternative interpretations in the General Discussion.

Memory for actions: Enactment and source memory

Enacting simple action phrases enhances item memory but may not enhance other aspects of memory. The present experiment examines the effects of enactment on source memory. During the study phase, participants performed some actions (subject-performed tasks, SPTs) and observed the experimenter perform other actions (experimenter-performed tasks, EPTs). One group performed the SPTs with eyes closed, one group with eyes open (the standard condition), and one group performed SPTs facing a mirror (EPT presentation was constant across groups). As expected, item memory was better for SPTs than for EPTs. More importantly, source memory for SPTs was affected by the amount of visual feedback. As predicted by the source-monitoring framework, source memory for SPTs decreased as the amount of visual feedback increased from none (eyes closed) to moderate (standard condition) to maximal (mirror condition). In addition, SPT encoding failed to increase source memory and in one condition actually decreased source memory, relative to EPT encoding. Thus, enactment dissociated item and source memory, enhancing the former but not the latter.

Generation and memory for contextual detail.

Generation enhances item memory but may not enhance other aspects of memory. In 12 experiments, the author investigated the effect of generation on context memory, motivated in part by the hypothesis that generation produces a trade-off in encoding item and contextual information. Participants generated some study words (e.g., hot-c__) and read others (e.g., hot-cold). Generation consistently enhanced item memory but did not enhance context memory. More specifically, generation disrupted context memory for the color of the target word but did not affect context memory for location, background color, and cue-word color. The specificity of the negative generation effect in context memory argues against a general item-context trade-off. A processing account of generation meets greater success. In addition, the results provide no evidence that generation enhances recollection of contextual details.