Continuous Memory Task Research Articles

Effects of Spacing of Item Repetitions in Continuous Recognition Memory: Does Item Retrieval Difficulty Promote Item Retention in Older Adults?

Background/Study Context: Older adults exhibit an age-related deficit in item memory as a function of the length of the retention interval, but older adults and young adults usually show roughly equivalent benefits due to the spacing of item repetitions in continuous memory tasks. The current experiment investigates the seemingly paradoxical effects of retention interval and spacing in young and older adults using a continuous recognition memory procedure. Methods: Fifty young adults and 52 older adults gave memory confidence ratings to words that were presented once (P1), twice (P2), or three times (P3), and the effects of the lag length and retention interval were assessed at P2 and at P3, respectively. Results: Response times at P2 were disproportionately longer for older adults than for younger adults as a function of the number of items occurring between P1 and P2, suggestive of age-related loss in item memory. Ratings of confidence in memory responses revealed that older adults remembered fewer items at P2 with a high degree of certainty. Confidence ratings given at P3 suggested that young and older adults derived equivalent benefits from the spacing between P1 and P2. Conclusion: Findings of this study support theoretical accounts that suggest that recursive reminding and/or item retrieval difficulty promote item retention in older adults.

Surrogate in-vehicle information systems and driver behaviour: Effects of visual and cognitive load in simulated rural driving

The underlying aim of HASTE, an EU FP5 project, is the development of a valid, cost-effective and reliable assessment protocol to evaluate the potential distraction of an in-vehicle information system on driving performance. As part of this development, the current study was performed to examine the systematic relationship between primary and secondary task complexity for a specific task modality in a particular driving environment. Two fundamentally distinct secondary tasks (or surrogate in-vehicle information systems, sIVIS) were developed: a visual search task, designed such that it only required visual processing/demand and an auditory continuous memory task, intended to cognitively load drivers without any visual stimulus. A high fidelity, fixed-base driving simulator was used to test 48 participants on a car following task. Virtual traffic scenarios varied in driving demand. Drivers compensated for both types of sIVIS by reducing their speed (this result was more prominent during interaction with the visual task). However, they seemed incapable of fully prioritising the primary driving task over either the visual or cognitive secondary tasks as an increase in sIVIS demand was associated with a reduction in driving performance: drivers showed reduced anticipation of braking requirements and shorter time-to-collision. These results are of potential interest to designers of in-vehicle systems.

Context Effects in the Measurement of Subjective Workload: Prolonged Exposure to the Same or Different Contexts

The present study investigated the effect of context on the subjective measurement of workload using the continuous memory task. Twelve levels of task difficulty were manipulated either between-subjects or within-subjects. Participants performed the continuous memory task for 48 trials under either a single difficulty level (between-subjects context) or under all 12 difficulty levels (within-subjects context). Workload was measured using ModSWAT— a technique that uses the sum of the SWAT dimensions to form the workload composite rather than the standard conjoint measurement procedure. Results indicated no difference in performance as a function of context but that context affected ratings of subjective workload. Under the single context condition, participants rated the workload of the easiest conditions higher than if the same conditions occurred within context of other more difficult conditions. Results are discussed in terms of their implication for practical assessment of subjective workload.

Effect of Pairted Comparison Weighting and Weighting Context

The present study compared three subjective workload measurement techniques—a unidimensional scale (UW) and two mutidimenional scales (TLX and ModSWAT)–using a continuous memory task. ModSWAT is a technique that uses the sum of the SWAT dimensions to form the workload composite rather than the standard conjoint measurement procedure. Both weighted and unweighted workload measures were obtained for the two multidimensional scales. The paired-comparison technique used by TLX was employed to weight the three SWAT dimensions. For both multidimensional scales, weighting context was also varied. Paired comparison of the workload dimensions was made either prior to the task in a general context or within context of the task just performed. The major findings were that: (1) ModSWAT and UW were more sensitive than TLX to the task demands (i.e., difficulty) of the continuous recognition task; (2) weighting context affected the weights that were assigned the workload dimensions for both TLX and ModSWAT; (3) weighting context did not affect the weighted workload scores; and (4) the weighted and unweighted workload composites were very similar. Results were interpreted within context of averaging across multiple dimensions when several dimensions are insensitive to the task demands. Variability in the weights assigned contributed to the failure to find a effect of weighting.

Dissociation of Storage and Rehearsal in Verbal Working Memory: Evidence From Positron Emission Tomography

Current cognitive models of verbal working memory include two components a phonological store and a rehearsal mechanism that refreshes the contents of this store We present research using positron emission tomography (PET) to provide further evidence for this functional division In Experiment 1, subjects performed a variant of Sternberg's (1966) item recognition task Experiment 2 used a continuous memory task with control conditions designed to separate the brain regions underlying storage and rehearsal The results show that independent brain regions mediate storage and rehearsal In Experiment 3, a dual-task procedure supported the assumption that these memory tasks elicited a rehearsal strategy

Dissociating verbal and spatial working memory using PET.

Three experiments used position emission tomography (PET) to study the neural basis of human working memory. These studies ask whether different neural circuits underly verbal and spatial memory. In Experiment 1, subjects had to retain for 3 sec. either the names of four letters (verbal memory) or the positions of three dots (spatial memory). The PET results manifested a clear cut double dissociation, as the verbal task activated primarily left-hemisphere regions whereas the spatial task activated only right-hemisphere regions. In Experiment 2, the identical sequence of letters was presented in all conditions, and what varied was whether subjects had to remember the names of the letters (verbal memory) or their positions in the display (spatial memory). In the verbal task, activation was concentrated more in the left than the right hemisphere; in the spatial task, there was substantial activation in both hemispheres, though in key regions, there was more activation in the right than the left hemisphere. Experiment 3 studied only verbal memory, and showed that a continuous memory task activated the same regions as the discrete verbal task used in Experiment 1. Taken together, these results indicate that verbal and spatial working memory are implemented by different neural structures.

Metabolic and cardiorespiratory measures of mental effort: the effects of level of difficulty in a working memory task

24 participants (12 female) performed a continuous memory task during which metabolic, cardiorespiratory, performance, and subjective mental workload measures were taken. Task difficulty was varied using two manipulations in a within-subjects factorial design: memory load (one or three items) and temporal demand (interstimulus intervals of 2, 3, or 4 s). Males and females differed in initial metabolic rate, but did not differ in their response to the task. Memory load affected all measures, while temporal demand affected only respiration rate, performance, and subjective mental workload. Metabolic, Respiratory, Cardiovascular, and Subjective/Performance components were identified in a principal components analysis (PCA), and the Respiratory and Subjective/Performance components were affected by the task manipulations. When performance quality was examined, the Metabolic component revealed that poor performers had greater energy expenditure during the task than good performers, and the Cardiovascular component revealed that good and poor performers differed in their response to memory load and temporal demand. Cardiac and metabolic changes during mental work were not a function of overall mental effort, but were specific to the effort due to memory load and to the individual differences among participants in their ability to perform the task. However, respiration was sensitive to the mental effort associated with both memory load and temporal demand, but was not sensitive to individual differences.

A Physical Measure of Subjective Workload

This investigation compared a physical measure of subjective workload (i.e., hand dynamometer) with traditional verbal scaling techniques. There were four subjective rating groups. One group employed the Subjective Workload Assessment Technique (SWAT) which required three separate ratings of time stress, mental effort, and psychological stress. A second group used verbal magnitude estimation (ME). Two physical measure groups estimated the magnitude of workload by squeezing a dynamometer in accordance with the magnitude of workload experienced. The DYNA1 group made one overall rating of workload similar to the ME group. The DYNA3 group made three workload ratings along the same dimensions as SWAT. All groups rated the workload associated with the performance of a continuous memory task under twelve levels of task difficulty. The physical measure of subjective workload most closely corresponded to actual task performance differences. The results suggest future development of a physical measure of subjective workload which can be utilized on a continuous basis, thus avoiding a major shortcoming of typical verbal measures of subjective workload.

Alternative Approaches to Analyzing SWAT Data

The present study sought to determine the sensitivity of three alternative approaches to deriving a workload composite measure based upon data gathered using the Subjective Workload Assessment Technique (SWAT) and to determine through the use of multivariate statistical procedures (MANOVA) if anything is to be gained by retaining the individual scale information of SWAT. The three rating scale dimensions of SWAT (time load, mental effort load, psychological stress load) were combined into a single workload composite using three techniques: conjoint measurement; a simple sum of the three scales weighted equally; an empirically determined weighted-linear combination of the three scales (from MANOVA). Using data gathered by having subjects perform a continuous memory task under twelve levels of task difficulty, it was found that the three composite measures were equally sensitive and highly correlated (the minimum correlation among the three composites being 0.9913). The results of the MANOVA performed on the same data indicated that the individual scales of SWAT were differentially sensitive to different task demands and that individual scale information should be retained rather than rely on a simple composite.

Retrieval of item frequency information in a continuous memory task.

The accuracy and response latency of absolute frequency judgments were measured as a function of test lag (the number of intervening items between presentations of a test item) in a continuous memory task. Frequency was varied from one to three presentations in Experiments 1 and 2 and from one to five presentations in Experiment 3. The proportion of correct responses decreased as frequency increased, and correct mean response time tended to increase with frequency. Both accuracy and correct mean response time were found to be largely a function of the most recent test lag. The lag-latency functions were best described by piecewise linear functions, with the breakpoint occurring between lags 1 and 2. Continuous frequency estimation was also shown to improve with extended practice. The implications of the results are discussed with reference to trace strength, numerical-inference, and multiple-trace theories of frequency discrimination.

Comparison of recognition and recall in a continuous memory task.

Differences between recall and recognition performance may be due at least in part to differences in the way information is stored. This possibility was explored in a paired-associate learning task by varying 6s knowledge at the time of study of how he would be tested on a particular stimulus-response pair. It was found that when 5 knew how he would be tested, his performance was better on recall but worse on recognition than when he did not know how he would be tested. These results were interpreted as support for the assertion that differences in storage processes partially account for recall-recognition performance differences. A model which postulates a distinction between short-term and long-term memory provided an excellent fit to the data and suggested possible storage strategies for recall and recognition.