Back to Psychophysiological Home Page International Journal of Psychophysiology 23 (1996) 18I-198 Relations_among96.doc Relations among memory performance, mental workload and cardiovascular responses Alex Vincent a * , Fergus I.M. Craik b, John J. Furedy b a Ergonomics Division, Transport Canada, Canada Building, 344 Slater Street, Ottawa, Ont. KIA ONS, Canada Department of Psychology, University of Toronto, Toronto, Canada Received 1 February 1996; revised 25 June 1996; accepted 23 July 1996 Abstract The levels of processing paradigm has been a powerful research framework in the study of memory for close to a quarter century. However, an objective index of depth of processing is still lacking. Two experiments using lists of words, presented to male subjects, were performed to compare the efects of depth of processing, rate of presentation, and task incentive on recognition memory performance, self-reported workload, and cardiovascular responding. Memory performance results from the two experiments demonstrated higher recognition levels associated with deeper processing and slower presentation rates. Deeply encoded items were associated with faster recognition latencies. Self-reported workload levels were higher for deeper processing and faster presentation rates. Cardiovascular responses were generally amplifed with the addition of a task incentive. Increased blood pressure was associated with faster presentation rates. Increased heart rate and decreased T-wave amplitude (i.e., increased sympathetic activity) were uniquely associated with the deep encoding of information presented at the fastest rate. This particular encoding condition was associated with increased recognition levels. Deeply encoded items were associated with increased suppression of heart rate variability during recognition. This combination of behavioral and cardiovascular measures may provide the basis for an objective index of depth of processing. 1. Introduction It is well established that diferent types of processing at the time of acquisition are associated with large diferences in later memory performance. These relations have been described and studied under the heading of levels of processing. The general idea is that material encoded semantically is better recalled than material encoded in terms of its 'shallower' phonological or visual features (Craik and Lockhart, * Corresponding author. e-mail: [email protected]; Fax: +1 (613) 9902913. 1972; Craik and Tulving, 1975). The levels of processing framework gives a good account of a number of important fndings in memory research, but it also sufers from several limitations, among them the absence of an independent index of depth of processing, and whether the efects of processing depth simply represent a byproduct of diferences in efort (Ellis et al., 1984; Tyler et al., 1979). Craik and Lockhart (1972) proposed that memory performance refected the depth, that is the degree of semantic analysis, to which encoded events were processed. However, Baddeley (1978) and others have pointed out the inherent circularity in the levels of processing formulation. In the absence of 182 A. Vincent et al. / International Journal of Psychophysiology 23 (1996) 181-198 an independent index 0167-8760/96/$15.00 Copyright 0 1996 Elsevier Science B.V. All rights reserved. PII SO167-8760(96)00058-X A. Vincent et al. / International Journal of Psychophysiology 23 (1996) 181-198 of 'depth', it is too easy to claim that any well-remembered event must have been processed deeply, simply because of the high level of memory performance. Psychophysiological and neuroimaging measures have the potential to break this circularity. If one or more of such measures can be shown to relate both to the degree of semantic involvement during the encoding process, and to the level of memory performance, it would put the concept of depth of processing on a more objective and rigorous footing. In fact, at least two studies have reported that diferences in depth of processing correlate with event-related potentials (Ferlazzo et al., 1993; Sanquist et al., 1980). Sanquist et al. studied the sensitivity of event-related potentials (ERPs) to depth of processing by measuring the ERPs to diferent encoding tasks varying in processing level and to a subsequent test of recognition memory. The ERPs difered among the three encoding tasks, with deeper processing being associated with greater ERP amplitude. The greatest amplitude of

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