Aspects of the theory of comprehension, memory and attention

This paper proposed a two-stage model to capture some basic relations between attention, comprehension and memory for sentences. According to the model, the first stage of linguistic processing is carried out in short-term memory (M₁) and involves a superficial analysis of semantic and syntactic features of words. The second stage is carried out in long-term memory (M₂) and involves application of transformational rules to the analyses of M₁ so as to determine the deep or underlying relations among words and phrases. According to the theory, attention is an M₂ process: preliminary analyses by M₁ are carried out even for unattended inputs, but final analyses by M₂ are only carried out for attended inputs. The theory was shown to be consistent with established facts concerning memory, attention and comprehension, and additional support for the theory was obtained in a series of dichotic listening experiments.     

An activity theory approach to memory

The articles which follow report independent research that originated in a collaborative group now organized as the Laboratory for Cognitive Studies of Work. Laboratory members are collectively engaged in working out a conceptual framework for cognitive research based on activity theory. Beach and Stevens, together with Scribner, elaborated this framework in the domain of memory, and in this introduction we will briefly sketch its principal implications for the ecological study of memory.     

Divided attention: An undesirable difficulty in memory retention

How can we improve memory retention? A large body of research has suggested that difficulty encountered during learning, such as when practice sessions are distributed rather than massed, can enhance later memory performance (see R. A. Bjork & E. L. Bjork, 1992). Here, we investigated whether divided attention during retrieval practice can also constitute a desirable difficulty. Following two initial study phases and one test phase with Swahili–English word pairs (e.g., vuvi–snake), we manipulated whether items were tested again under full or divided attention. Two days later, participants were brought back for a final cued-recall test (e.g., vuvi–?). Across three experiments (combined N = 122), we found no evidence that dividing attention while practicing retrieval enhances memory retention. This finding raises the question of why many types of difficulty during practice do improve long-term retention, but dividing attention does not.     

Visual-spatial working memory, attention, and scene representation: A neuro-cognitive theory

This paper addresses the issue of how visual-spatial working memory, attention, and scene representation are related. The first section introduces a modified two-stage conception of visual-spatial processing. “Stage one” refers to low-level visual-spatial processing and computes in parallel for the currently available retinal information “object candidates,” here called “visual-spatial units.” An attentional process called “unit selection” allows access to stage two for one of these units at a time. Stage two contains high-level visual-spatial information that can be used for goal-directions (e.g., verbal report, grasping). It consists of three parallel processing streams. First, the currently selected unit is recognized; second, a spatial-motor program for the selected unit is computed; and third, an “object file” is set up for the selected unit. An object file contains temporary episodic representations of detailed high-level visual-spatial attributes of an “object” plus an “index.” An index acts as a pointer and is bound via temporary connections to the attributes of the file. Section two of this paper specifies one part of stage two in more detail, namely visual-spatial working memory (VSWM). It can contain up to four object files. A first central claim is that during sensory-based processing for working memory (“access”), one object file is always “on-line,” and up to three other object files are “off-line”. A second central claim is that the process of setting up an object file depends on the number and the activation level of already stored files. Based on the concept of activation-based competition between object files, it is postulated that the more files that are stored and the higher their activation is, the longer it takes for a newly set up object file to reach a sufficient level of activation. Activation-based competition is also used to explain “short-term forgetting” by “interference.” A third central claim about VSWM is that a “refreshment' process exists that increases the activation level of an index of an object file in order to prevent forgetting or in order to bring the file back to the state of controlling the current action. Finally, section three gives a selective look at a number of experimental data such as the attentional blink, backward masking, dwell time effects, transsaccadic memory, and change blindness. New explanations are offered and new predictions made. Received: 16 January 1998 / Accepted: 25 July 1998     

Working memory and focal attention

Measures of retrieval speed indicated that only a small subset of representations in working memory falls within the focus of attention. An n-back task, which required tracking an item 1, 2, or 3 back in a sequentially presented list, was used to examine the representation and retrieval of recent events and how control processes can be used to maintain an item in focal attention while concurrently processing new information. A speed-accuracy trade-off procedure was used to derive measures of the availability and the speed with which recent events can be accessed. Results converge with other time course studies in demonstrating that attention can be concurrently allocated only to a small number of memory representations, perhaps just 1 item. Measures of retrieval speed further demonstrate that order information is retrieved by a slow search process when an item is not maintained within focal attention.     

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.     

Working memory,sustained attention,and physical activity: An intraindividual study

ObjectiveExperimental studies show small to moderate effects of both acute and regular physical activity on executive functions, these being strongly associated with academic performance at school. In order to understand the naturally occurring associations between primary school-aged children’s working memory, self-reported sustained attention, and physical activity, 35 children (M_age = 9.8 years, range = 7.6–11.4 years old) in Years 3–6 of primary school took part in a two-week long intraindividual study.MethodsParticipants wore an accelerometer wristband throughout the study, and carried out a working memory task (digit recall) and completed a sustained attention measure each morning and afternoon, giving 517 time-points nested in 4–10 school-days (M_obs = 15.8 situations, n_obs = 4–18).ResultsUsing multilevel structural equation models (MSEM), we found that working memory was stable across time (within-person b = 0.29) and trait-like (ICCs = 0.58). Across situations, state-working memory was higher later in the calendar week. Acute moderate to vigorous physical activity (MVPA) was not associated with state-working memory, but exertion of a higher level of MVPA than usual the previous day was associated with lower state-working memory the following day. Trait-sustained attention (across the two weeks) predicted higher trait-working memory and older students outperformed younger students.ConclusionsImplications for timing and intensity of students’ physical activity in educational settings is discussed.     

Serial attention within working memory

It is proposed that people are limited to attending to just one “object” in working memory (WM) at any one time. Consequently, many cognitive tasks, and much of everyday thought, necessitate switches between WM items. The research to be presented measured the time involved in switching attention between objects in WM and sought to elaborate the processes underlying such switches. Two experiments required subjects to maintain two running counts; the order in which the counts were updated necessitated frequent switches between them. Even after intensive practice, a time cost was incurred when subjects updated the two counts in succession, relative to updating the same count twice. This time cost was interpreted as being due to a distinct switching mechanism that controls an internal focus of attention large enough for just one object (count) at a time. This internal focus of attention is a subset of WM (Cowan, 1988). Alternative visual and conceptual repetition-priming and memory retrieval explanations for the cost involved in switching between items in WM are addressed.     

Movement and attention in visual working memory

Three experiments that adopt an interference technique to investigate the involvement of movement in the production of a spatial code are described. Arm movements rather than the more commonly employed eye movements are used to provide initial information about the sorts of movements relevant to the code and to allow an empirical separation of the contributions of movement and attention. The results confirm the interference effects of incompatible movement on the generation of the spatial code and show that movement per se rather than attention to the movement can cause a performance decrement.     

Interference between object-based attention and object-based memory

Research has shown that there are at least two kinds of visual selective attention: location based and object based. In the present study, we sought to determine the locus of spatially invariant object-based selection using a dual-task paradigm. In four experiments, observers performed an attention task (object feature report or visual search) with a concurrent memory task (object memory or spatial memory). Object memory was interfered with more by a concurrent object-based attention task than by a concurrent location-based attention task. However, this interference pattern was reversed for spatial memory, with greater interference by a location-based attention task than by an object-based attention task. These findings suggest that object-based attention and locationbased attention are functionally dissociable and that some forms of object-based selection operate within visual short-term memory.     

Activation,attention, and short-term memory

The premise of this paper is that the popular term “short-term memory” (STM) is vague because it is used to refer to either (1) the set of representations from long-term memory currently in a state of heightened activation or (2) the focus of attention or content of awareness. A more coherent conception of STM is hierarchical, with the focus of attention depicted as a subset of the activated portion of long-term memory. Research issues are discussed to illustrate that this simple conception of STM leads to testable predictions and useful lines of inquiry.     

A feature-integration theory of attention

A new hypothesis about the role of focused attention is proposed. The feature-integration theory of attention suggests that attention must be directed serially to each stimulus in a display whenever conjunctions of more than one separable feature are needed to characterize or distinguish the possible objects presented. A number of predictions were tested in a variety of paradigms including visual search, texture segregation, identification and localization, and using both separable dimensions (shape and color) and local elements or parts of figures (lines, curves, etc. in letters) as the features to be integrated into complex wholes. The results were in general consistent with the hypothesis. They offer a new set of criteria for distinguishing separable from integral features and a new rationale for predicting which tasks will show attention limits and which will not.     

A theory of visual attention

A unified theory of visual recognition and attentional selection is developed by integrating the biased-choice model for single-stimulus recognition (Luce, 1963; Shepard, 1957) with a choice model for selection from multielement displays (Bundesen, Pedersen, & Larsen, 1984) in a race model framework. Mathematically, the theory is tractable, and it specifies the computations necessary for selection. The theory is applied to extant findings from a broad range of experimental paradigms. The findings include effects of object integrality in selective report, number and spatial position of targets in divided-attention paradigms, selection criterion and number of distracters in focused-attention paradigms, delay of selection cue in partial report, and consistent practice in search. On the whole, the quantitative fits are encouraging.     

Dual-process theory and signal-detection theory of recognition memory

Two influential models of recognition memory, the unequal-variance signal-detection model and a dual-process threshold/detection model, accurately describe the receiver operating characteristic, but only the latter model can provide estimates of recollection and familiarity. Such estimates often accord with those provided by the remember-know procedure, and both methods are now widely used in the neuroscience literature to identify the brain correlates of recollection and familiarity. However, in recent years, a substantial literature has accumulated directly contrasting the signal-detection model against the threshold/detection model, and that literature is almost unanimous in its endorsement of signal-detection theory. A dual-process version of signal-detection theory implies that individual recognition decisions are not process pure, and it suggests new ways to investigate the brain correlates of recognition memory.     

Overlapping mechanisms of attention and spatial working memory

Spatial selective attention and spatial working memory have largely been studied in isolation. Studies of spatial attention have provided clear evidence that observers can bias visual processing towards specific locations, enabling faster and better processing of information at those locations than at unattended locations. We present evidence supporting the view that this process of visual selection is a key component of rehearsal in spatial working memory. Thus, although working memory has sometimes been depicted as a storage system that emerges 'downstream' of early sensory processing, current evidence suggests that spatial rehearsal recruits top-down processes that modulate the earliest stages of visual analysis.     

Working memory and flexibility in awareness and attention

We argue that attention and awareness form the basis of one type of working-memory storage. In contrast to models of working memory in which storage and retrieval occur effortlessly, we document that an attention-demanding goal conflict within a retrieval cue impairs recall from working memory. In a conceptual span task, semantic and color-name cues prompted recall of four consecutive words from a twelve-word list. The first-four, middle-four, and final-four words belonged to different semantic categories (e.g., body parts, animals, and tools) and were shown in different colors (e.g., red, blue, and green). In Experiment 1, the color of the cue matched that of cued items 75% of the time, and the rare mismatch impaired recall. In Experiment 2, though, the color of the cue matched that of the cued items only 25% of the time, and the now-more-frequent mismatches no longer mattered. These results are difficult to explain with passive storage alone and indicate that a processing difficulty impedes recall from working memory, presumably by distracting attention away from its storage function.     

How verbal memory loads consume attention

According to a traditional assumption about working memory, participants retain a series of verbal items for immediate recall using covert verbal rehearsal, without much need for attention. We reassessed this assumption by imposing a speeded, nonverbal choice reaction time (CRT) task following the presentation of each digit in a list to be recalled. When the memory load surpassed a few items, performance on the speeded CRT task became increasingly impaired. This CRT task impairment depended only on attention-related components of working memory; it was not alleviated by the presence of an auditory memory trace that automatically helped the recall of items at the ends of spoken lists. We suggest that attention-demanding refreshing of verbal stimuli occurs along with any covert rehearsal.