Academic journal article Memory & Cognition

The Validity of "Conceptual Span" as a Measure of Working Memory Capacity

Academic journal article Memory & Cognition

The Validity of "Conceptual Span" as a Measure of Working Memory Capacity

Article excerpt

Three experiments tested whether a modified version of the Clustered Conceptual Span task (H. J. Haarmann, E. J. Davelaar, & M. Usher, 2003), which ostensibly requires active maintenance of semantic representations, predicted individual differences in higher-order cognitive abilities better than short-term memory (STM) span tasks or nonsemantic versions of the "Conceptual" task did. Nonsemantic Conceptual tasks presented short word lists clustered by color, first letter, or initial vowel sound, and cued subjects to recall only 1 of 3 clusters from each list; the Semantic task clustered words by taxonomic category. The Semantic Conceptual task generally failed to predict incremental variance in either verbal abilities or general fluid intelligence beyond the other Conceptual tasks or STM span tasks. Although the Semantic task showed a stronger relation to working memory span tasks than did the nonsemantic tasks (Experiment 3), that stronger relation did not translate into strong prediction of cognitive individual differences.

Individual differences in short-term memory (STM) capacity are traditionally assessed with "span" tasks that present short sequences of items, such as digits or words, for the subject to immediately recall in serial order (Jacobs, 1887; Dempster, 1981). Although these tasks are often referred to as "simple" span tasks (e.g., La Pointe & Engle, 1990; Turner & Engle, 1989), they have prompted a host of competing and complex theoretical models of serial-order memory (e.g., Burgess & Hitch, 1999; Farrell & Lewandowsky, 2002; Henson, 1998; Neath & Nairne, 1995; Page & Norris, 1998). Experimental and neuropsychological work also suggests that dissociable storage systems for phonological and lexical-semantic information contribute to a variety of verbal STM tasks (e.g., Crosson et al., 1999; Haarman & Usher, 2001; Hanten & Martin, 2000; Martin & Romani, 1994; Tehan & Lalor, 2000; for a review, see Martin & Freedman, 2001). Based on the idea that a dedicated memory system for maintaining access to lexical-semantic representations might be especially important to successful language comprehension and verbal problem solving, Haarmann, Davelaar, and Usher (2003) developed a new span task, "Conceptual Span," to measure variation in semantic STM and its association to verbal abilities. The present study critically explores the construct validity of Conceptual Span as an individual-differences measure of immediate-semanticmemory capacity.

The Conceptual Span Task

Traditional STM tasks require verbatim repetition of unrelated stimuli in sequential order, and thus encourage subjects to phonologically rehearse the items via inner speech (e.g., Baddeley, Gathercole, & Papagno, 1998; Baddeley, Lewis & Vallar, 1984). In contrast, Conceptual Span was designed to orient subjects' maintenance and retrieval processes toward stimulus meaning. One version of the task presented lists of 9 randomly ordered words that belonged to 3 different semantic categories (e.g., animals,furniture, and fruit), and another "clustered" version presented lists of 12 semantically clustered words, with 4 consecutive words from each category. In both, subjects immediately recalled only the words from one cued category (e.g., furniture) in any order, thereby minimizing the importance of serial order and the contribution of phonological processing, and maximizing the role of semantic processing.

Haarmann et al. (2003) found that Conceptual Span predicted variation in reasoning and comprehension more strongly than did STM span tasks which, because they presented either words or pronounceable nonwords, engaged primarily phonological processes. Thus, semantic STM did appear to support complex verbal behavior. Moreover, and perhaps most surprisingly, Conceptual Span predicted verbal individual differences as strongly, if not more strongly, than a Reading Span task did. Reading span is a "complex" working memory (WM) span task that requires subjects to memorize short stimulus sequences that are interpolated with a secondary task, such as reading sentences. …

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