Elsevier

Acta Psychologica

Volume 136, Issue 3, March 2011, Pages 329-339
Acta Psychologica

The relationship between divided attention and implicit memory: A meta-analysis

https://doi.org/10.1016/j.actpsy.2010.12.007Get rights and content

Abstract

This article reports a meta-analysis comparing the size of repetition priming in full and divided-attention (DA) conditions. The main analysis included 38 effect sizes (ES) extracted from 21 empirical studies, for a total of 2074 (full-attention) and 2148 (divided-attention) participants. The mean weighted ES was 0.357 (95% CI = 0.278–0.435), indicating that divided attention produced a small, but significant, negative effect on implicit memory. Overall, the distinction between identification and production priming provided the best fit to empirical data (with the effect of DA being greater for production tests), whereas there was no significant difference between perceptual and conceptual priming. A series of focused contrasts suggested that word-stem completion might be influenced by lexical–conceptual processes, and that perceptual identification might involve a productive component. Implications for current theories of implicit memory are discussed.

Introduction

A great research effort has been devoted to the study of the relationship between attention and implicit memory (see Mulligan and Brown, 2003, Rajaram, 2007, for reviews). Indirect memory tasks differ from explicit ones because they do not require intentional retrieval of the encoded information. Learning is typically demonstrated by an increase of the accuracy and/or speed of elaboration, identification and generation of studied vs. unstudied stimuli (Stone, Ladd, Vaidya & Gabrieli, 1998). Early studies suggested that divided attention (DA) at encoding had differential effects on implicit and explicit memory. This manipulation reduced performance in tasks of free recall and recognition (Craik, Govoni, Naveh-Benjamin, & Anderson, 1996), whereas it had no effects on implicit tests (Kellogg et al., 1996, Parkin et al., 1990, Parkin and Russo, 1990, Russo and Parkin, 1993, Schmitter-Edgecombe, 1996, Szymanski and MacLeod, 1996). However, subsequent experiments found a number of exceptions (Gabrieli et al., 1999, Light and Prull, 1995, Mulligan and Hartman, 1996, Mulligan, 1997, Mulligan, 1998, Wolters and Prinsen, 1997). The present meta-analysis was specifically aimed at testing a number of different explanations about the effects of DA manipulations on implicit memory. In particular, the primary aim was to ascertain whether incongruent results could be reconciled by taking into account the nature of implicit tests (based on perceptual vs. conceptual or on identification vs. production processes) and the difficulty of interference tasks. These issues are briefly illustrated in the following paragraphs. In addition, two separate sections will be dedicated to the discussion of the problems concerning task classification and the use of different types of dependent variables.1

Section snippets

Perceptual vs. conceptual priming

The Transfer Appropriate Processing (TAP) theory proposes that memory performance will improve when the cognitive processes carried out during encoding are reengaged at test, and distinguishes between data-driven and conceptually-driven tasks (Blaxton, 1989, Roediger et al., 1989). Indirect tests based on conceptual processes, like category exemplar generation, require the analysis and retention of the meaning of the stimuli, whereas indirect tests based on perceptual processes, like

Identification vs. production priming

On the basis of convergent behavioral and neuropsychological findings, Gabrieli et al. (1999) proposed to distinguish between identification and production forms of repetition priming. Identification tasks (like perceptual identification and lexical decision) require to identify target items or verify their attributes: in these conditions the test cues directly guide the retrieval processes toward unique appropriate responses. In contrast, the retrieval stimuli employed in production tasks

Task classification

Both the dichotomies outlined in the previous sections are based on the classification of implicit tasks into separate categories. However, the criteria employed to make these distinctions are neither clear nor unambiguous, so that different researchers classify the same tasks into different classes. In particular, there has been considerable debate about the nature of the Word-Stem Completion (WSC) task. In their influential review, Roediger and McDermott (1993) included it in the perceptual

Type of dependent variable

Fleischman et al. (2001) raised the possibility that the comparison between identification and production priming might be confounded by differences in the type of dependent variable employed (Light, Prull, La Voie, et al., 2000, Mulligan and Peterson, 2008, Prull, 2004). This happens because virtually all production tasks rely on accuracy measures (e.g., changes in the proportions of correct responses), whereas many identification tasks (lexical decision, category exemplar verification,

Difficulty of secondary tasks

A number of authors (Mulligan, 1997, Wolters and Prinsen, 1997) proposed that the contradictory results obtained by experiments studying the DA effects on implicit memory could be partially accounted for by considering the level of difficulty of the secondary tasks. Wolters and Prinsen (1997) compared the effects of DA on word-stem cued recall and word-stem completion, manipulating both the difficulty and the modality of presentation (visual/auditory) of interference tasks. In the easy

Aims and predictions

The aims of the present meta-analysis were threefold. The first general issue was to understand whether implicit memory is exclusively based on automatic encoding processes (Eich, 1984, Isingrini et al., 1995, Jelicic et al., 1992, Parkin and Russo, 1990, Parkin et al., 1990), or whether it requires some amount of attentional resources. This was accomplished by testing whether the average DA effect was significantly greater than zero.

Narrative reviews would have difficulties in reaching the

Method

Relevant studies were identified through different methods: (a) manual search of journals known to publish experimental studies on attention and implicit memory (Journal of Experimental Psychology: Learning, Memory and Cognition; Memory and Cognition; Memory; Journal of Memory and Language; European Journal of Cognitive Psychology); (b) check of references from empirical studies and reviews; (c) computerized search of PsycInfo, using the key words: attention, divided attention, repetition

Results

Data were analyzed using the SPSS macros provided by Wilson (Lipsey & Wilson, 2000). The general method was that outlined by Hedges and Olkin (1985). The first step was to compute an overall homogeneity index QT, to determine whether all studies shared a common effect size. If this value was significant (allowing to reject the null hypothesis of homogeneity), experiments were partitioned into categories based on theoretically relevant grouping factors. If the within-class homogeneity statistic Q

The status of word stem completion and perceptual identification tasks

As discussed in the Introduction, several researchers hypothesized that WSC performance might be heavily influenced by conceptual processes (Clarys et al., 2000, Gabrieli, 1991, Keane et al., 1991). Table 5 illustrates the mean effect sizes for each implicit task included in the present meta-analysis: it can be seen that the ES corresponding to WSC (d = 0.561) is consistently greater than that of the whole perceptual category (d = 0.306), and only slightly lower than the mean ES of category

The role of dependent variable

In the present meta-analysis only six studies employed latency measures (all of them being classified into the identification category): when this set of experiments was compared with the remaining 32 studies, an inverse variance weighted one-way ANOVA revealed no reliable difference between the two groups [QB (1) = 0.78, p = 0.38] but a marginally significant within-class heterogeneity [QW (36) = 48.43, p = 0.08]. Complete homogeneity was reached by deleting two effect-sizes from the group of

General discussion

The present meta-analysis was aimed at assessing whether the contradictory results obtained in studies investigating the effects of DA on implicit memory could be explained by one or more of the theoretical frameworks currently available in the literature. Statistical analyses showed several relevant points, which will be discussed in the following sections.

Conclusions

Summing up, the present meta-analysis showed that DA at encoding produced a negative, albeit mild, effect on indirect tasks, contradicting the idea that implicit memory is exclusively based on automatic encoding processes (Parkin et al., 1990). More importantly, it turned out that the model representing the distinction between identification and production priming provided the best fit with empirical data, whereas the numerical difference between perceptual and conceptual priming was unreliable.

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