Effects of dividing attention on the memory-block effect

S. M. Smith and D. R. Tindell (1997) reported that prior study of words that are orthographically similar to the solutions of test word fragments (e.g., studying ANALOGY and completing the fragment A_L _ _GY, whose solution is ALLERGY) reduced the fragment completion rate relative to a baseline condition in which unrelated words were studied. They called this effect the memory-block effect. In the present experiment, the authors replicated this effect using a larger set of materials than that used by S. M. Smith and D. R. Tindell. The authors also found that dividing attention at study eliminated the memory-block effect. This pattern mimicked the effect of dividing attention on recognition memory but differed from the effect on repetition priming effects. The authors suggest that the memory-block effect is driven by a mechanism different from that responsible for producing repetition priming effects in an implicit fragment completion test.     

Stimulus timing by people with Parkinson's disease

Previous literature suggests that Parkinson’s disease is marked by deficits in timed behaviour. However, the majority of studies of central timing mechanisms in patients with Parkinson’s disease have used timing tasks with a motor component. Since the motor abnormalities are a defining feature of the condition, the status of timing in Parkinson’s disease remains uncertain. Data are reported from patients with mild to moderate Parkinson’s disease (both on and off medication) and age- and IQ-matched controls on a range of stimulus timing tasks without counting. Tasks used were temporal generalization, bisection, threshold determination, verbal estimation, and a memory for duration task. Performance of patients was generally “normal” on all tasks, but significant differences from performance of controls were found on the memory for duration task. Among the “normal” effects noted were arithmetic mean bisection, asymmetric temporal generalization gradients, and subjective shortening on the memory for duration task. The results suggest (a) that some previous reports of timing “deficits” in Parkinson’s patients were possibly due to the use of tasks requiring a timed manual response and (b) small differences between patients and controls may be found on tasks where two stimuli are presented on each trial, whether patients are on medication or off it.     

The role of attention in different visual-search tasks

Observers viewed displays containing a variable number of distractors of one color and a target of another color. In some experiments, the target and distractors maintained their color from trial to trial; in others, they reversed unpredictably. Observers made a speeded two-choice judgment concerning either the presence, the color, or the shape of the odd-colored target. With only one exception, all of these conditions produced the same pattern of results: reaction times remained constant as the number of distractors increased. The exceptional result occurred when observers judged the shape of the odd-colored target and the color of the target and distractors reversed unpredictably. In this case, reaction times decreased as the number of distractors increased. These results are interpreted in terms of the attentional requirements of the different judgments and the mechanisms that guide attention.     

Cognitive slowing in decision tasks in early and advanced Parkinson's disease.

Ten untreated patients with recently diagnosed Parkinson's disease (PD), 9 treated patients with more advanced pathology, and 17 matched normal controls were investigated with three reaction tasks with increasing cognitive load but identical motor requirements: simple reaction, choice reaction with indicative stimuli, and choice reaction with ambiguous stimuli. Times required until a home key was released (= reaction time) and from then until a response key was pressed (= movement time) were recorded. Estimates of pure decision time (overall response time minus movement time in a simple reaction time task) revealed a difference between advanced and early PD patients. Advanced PD patients showed an overall slowing of decision time in the reaction time tasks, but the effect of the cognitive load of the tasks on the decision time was comparable to a control group. The untreated early PD patients performed quite normally in the more simple decision tasks but showed a disproportionate slowing of decision time in tasks with higher cognitive load.     

The deployment of attention in short-term memory tasks: Trade-offs between immediate and delayed deployment

Memory at times depends on attention, as when attention is used to encode incoming, serial verbal information. When encoding and rehearsal are difficult or when attention is divided during list presentation, more attention is needed in the time following the presentation and just preceding the response. Across 12 experimental conditions observed in several experiments, we demonstrated this by introducing a nonverbal task with three levels of effort (no task, a natural nonverbal task, or an unnatural version of the task) during a brief retention interval in a short-term digit recall task. Interference from the task during the retention interval was greater when resources were drawn away from the encoding of the stimuli by other factors, including unpredictability of the end point of the list, rapid presentation, and a secondary task during list presentation. When those conditions complicate encoding of the list, we argue, attention is needed after the list so that the contents of passive memory (i.e., postcategorical phonological storage and/or precategorical sensory memory) may be retrieved and become the focus of attention for recall.     

The role of attention in different visual-search tasks.

Observers viewed displays containing a variable number of distractors of one color and a target of another color. In some experiments, the target and distractors maintained their color from trial to trial; in others, they reversed unpredictably. Observers made a speeded two-choice judgment concerning either the presence, the color, or the shape of the odd-colored target. With only one exception, all of these conditions produced the same pattern of results: reaction times remained constant as the number of distractors increased. The exceptional result occurred when observers judged the shape of the odd-colored target and the color of the target and distractors reversed unpredictably. In this case, reaction times decreased as the number of distractors increased. These results are interpreted in terms of the attentional requirements of the different judgments and the mechanisms that guide attention.     

The effect of novel distractors on performance in focused attention tasks: A cognitive-psychophysiological approach

In the present study, we examined whether or not novel stimuli affect performance in a focused attention task. Participants responded to a central target while an irrelevant distractor in the visual display was occasionally changed. In Experiment 1, both target and distractor were presented centrally within the focus of attention. In Experiment 2, a central target was presented along with an irrelevant distractor at a peripheral location, outside the focus of attention. Novel distractors were associated with longer latencies and enhanced orienting responses (as measured by skin conductance responses) only when presented at an attended location. In contrast, as is demonstrated in Experiment 3, the same peripheral novel distractors interfered with task performance when they possessed task-relevant information. These results indicate that there is a fundamental difference between novel stimuli and task-relevant stimuli. Whereas the former exert influence only within the focus of attention, the latter affect performance even when positioned in an unattended location. Our findings have important implications for the operation of visual attention.     

Effect of click trains on duration estimates by people with Parkinson's disease

Patients with a diagnosis of Parkinson's disease and age- and IQ-matched controls estimated the duration of short 500-Hz tones (325–1,225 ms), on trials where the tone was either preceded by 3 s of 5-Hz clicks, or presented without clicks. The click manipulation had been shown in earlier studies with student participants to make verbal estimates longer. Patients were tested both on and off their dopaminergic medication, and controls were also tested in two sessions. Verbal estimates were markedly and significantly longer on trials with clicks than on those without clicks for both the patients and the controls, but there were no significant performance differences between patients or controls, nor between the on and off medication sessions in the patients. The study shows that a manipulation of subjective time, which has had small but consistent effects in student participants, also affects timing in patients and adds to a growing body of evidence that timing in patients with Parkinson's disease may in many cases have the same characteristics as those of neurologically intact control groups.     

Effect of click trains on duration estimates by people with Parkinson's disease

Patients with a diagnosis of Parkinson's disease and age- and IQ-matched controls estimated the duration of short 500-Hz tones (325-1,225 ms), on trials where the tone was either preceded by 3 s of 5-Hz clicks, or presented without clicks. The click manipulation had been shown in earlier studies with student participants to make verbal estimates longer. Patients were tested both on and off their dopaminergic medication, and controls were also tested in two sessions. Verbal estimates were markedly and significantly longer on trials with clicks than on those without clicks for both the patients and the controls, but there were no significant performance differences between patients or controls, nor between the on and off medication sessions in the patients. The study shows that a manipulation of subjective time, which has had small but consistent effects in student participants, also affects timing in patients and adds to a growing body of evidence that timing in patients with Parkinson's disease may in many cases have the same characteristics as those of neurologically intact control groups.     

Sentence comprehension in Parkinson's disease: the role of attention and memory.

Sentence comprehension is a complex process involving at least attentional, memory, grammatical, and semantic components. We report three experiments designed to evaluate the impairments underlying sentence comprehension difficulties in nondemented patients with Parkinson's disease (PD). In the first experiment, we asked patients to answer simple questions about sentences which varied in terms of grammatical complexity and semantic constraint. We found that PD patients are significantly compromised in their ability to perform this task. Their difficulties became more prominent as grammatical complexity increased, but they were significantly assisted by semantic constraints that limited possible interpretations of a sentence. Analyses of individual patient profiles revealed heterogeneous performance across the group of PD patients and somewhat inconsistent performance for patients across testing sessions. In the second experiment, we tested the possibility that patients' heterogeneous performance on the sentence comprehension task is due to an impairment in memory or attention, cognitive domains known to be compromised in some PD patients. Although PD patients and control subjects differed on one memory measure, there were no significant correlations between attention and memory performance and the results of the sentence comprehension task. In the final experiment, we manipulated the sentences used in the first experiment in a fashion that stressed the need for memory and attention in a sentence. The results indicated that PD patients are significantly compromised in their ability to attend to certain critical grammatical features of a sentence. A regression analysis identified specific grammatical, semantic, and attentional mechanisms as significant contributors to PD patients' overall sentence comprehension, accounting for over 97% of the variance in their performance. We conclude that there are multiple sources of cognitive difficulty underlying PD patients' sentence comprehension impairment.     

The phonological-similarity effect differentiates between two working memory tasks

Working memory is a set of interactive cognitive processes that maintain information on–line and available for analysis. Part of the system is specialized for maintaining verbal information, a core component of which is thought to be a phonological store. On the basis of the study of patients with acquired brain lesions, this store has been localized to the supramarginal and angular gyri of the speech–dominant hemisphere, and some functional neuroimaging studies support this localization. However, other imaging studies localize the phonological store in a more dorsal region of the parietal lobe. To reconcile these findings, we examined the phonological–similarity effect in two different tasks. A phonological–similarity effect was observed only in the task that involved sequential presentation and explicit verbal rehearsal. We conclude that at least one possible source of the differences in brain activation between different working memory tasks may be differences in phonological processing.     

The relationship between executive function and verbal memory in Parkinson's disease

A growing body of evidence suggests that the various cognitive symptoms found in Parkinson's disease (PD) are secondary to executive dysfunction. Studies addressing this possibility for memory impairment specifically have not included measures of working memory nor have they ruled-out potential mediating variables such as overall level of cognitive impairment or depression. The purpose of this study was to include measures of these variables in determining the relationship between multiple aspects of executive function and delayed verbal recall in 32 idiopathic PD patients. Results were consistent with the original hypothesis and further suggest that working memory is a key factor in recall memory and may mediate the relationship between other executive measures and recall in PD.     

The development of perceived structure and attention: evidence from divided and selective attention tasks

Three experiments provide converging evidence for the view that both perceived structure and attention change during the elementary school years. Kindergarteners, second graders, and adults performed three speeded tasks: divided attention to conjunctions of features, selective attention to orthogonal dimensions and selective attention to correlated dimensions. The tasks were performed with sizes and shapes that were either spatially integrated or spatially separated. In the divided attention task, conjunctions were identified as quickly as single features with integrated stimuli at all ages, but conjunctions were identified more slowly than single features with separated stimuli by all age group. In the orthogonal dimensions task, interference was observed with integrated stimuli across ages, but the interference in adult performance was asymmetric. With separated stimuli, interference was gradually eliminated with increasing age. In correlated dimensions tasks, younger children showed a redundancy gain with integrated stimuli, but no gain was observed in the performances of the older subjects. With separated stimuli there was no redundancy gain at any age. These results were interpreted to mean that integrated stimuli are initially perceived as wholes by all subjects, but that features become more accessible with increasing age. Even so, attention remains constrained by stimulus structure. In contrast, separated stimuli are initially perceived as features at all ages, and the improvement in performance with increasing age is attributable to the increasing command of attentional resources that accompanies development. Our discussion of these findings focuses on three issues: multiple trends in perceptual development, the characteristics of an adequate theory of perceptual representation and processing, and a comparison of the separability hypothesis and other developmental accounts of perceptual development.     

Independent mechanisms for dividing attention between the motion and the color of dynamic random dot patterns

The present study investigated the division of attention between different visual attributes, which is a cognitive function implicated in the selection of information in a given condition. To examine the underlying mechanisms, we focused on motion and color as visual attributes. In Experiment 1, performance on single- and dual-judgment for motion and color of dynamic random dot patterns presented in a restricted visual field was examined under different priority conditions. Accuracy was the same for single- and dual-task conditions, and the attention operating characteristic (AOC) analysis indicated that motion and color perception do not share the same processing capacity. In addition, correlation analysis indicated that, on a trial-by-trial basis, performance on motion and color was considerably independent. In Experiment 2, a brief lateral cue preceded the dynamic random dot patterns. The cue affected only motion-judgment, even under dual-task conditions of motion and color. These results suggest that dividing attention between motion and color involves independent mechanisms.     

The gender-congruency effect in picture-word tasks

In Dutch noun phrases like “het boek” (the book) or “de kat” (the cat), the definite article (het or de) depends on the noun's grammatical gender (neuter or non-neuter). Schriefers reported that the production of a noun phrase like “het rode bed” (“the red bed”) in response to a colored picture takes less time when the picture is accompanied by a distractor word of congruent gender (e.g., “huis,” a het-word) than when it is accompanied by a word of incongruent gender (e.g., “hand,” a de-word). In three experiments we explored the characteristics of this gender-congruency effect. The following conclusions were reached. First, the gender-congruency effect is a rather robust phenomenon. Second, with the exception of a small effect in Exp. 2, no evidence was obtained for a gender-congruency effect when subjects were required to produce a single noun in response to a picture (e.g., “bed”). Third, the gender-congruency effect decreases with a decreasing familiarity of the distractor word. Implications for models of word production are discussed. Received: 20 May 1997 / Accepted: 25 September 1997     

The effect of Parkinson's disease on the control of multi-segmental coordination

An experiment was designed to test whether or not Parkinson's disease (PD) patients were able to maintain endpoint kinematic patterns in a prehension task involving movement of the torso. Nine PD patients and nine healthy controls were asked to reach for and grasp a full cup of water that was either covered or uncovered and placed beyond the reach of the outstretched arm. An OPTOTRAK (Northern Digital) 3-dimensional motion analysis system was used to capture the movement of four markers placed on the arm, hand, and torso. The results indicated the Parkinson's patients had a decreased ability to maintain the kinematics of the end effector. The PD patients were also found to be impaired in terms of their ability to synchronize the arm, hand, and torso. More specifically, although the elderly controls seemed to employ a strategy of increasing the involvement of the torso when reaching to grasp the uncovered cup, no such strategy was observed in the PD patients. Collectively, the results suggest that the multi-joint synergies observed in the elderly controls, which help preserve relatively consistent endpoint trajectories, are disrupted in Parkinson's patients.     

Endogenous temporal orienting of attention in detection and discrimination tasks

Endogenous temporal-orienting effects were studied using a cuing paradigm in which the cue indicated the time interval during which the target was most likely to appear. Temporal-orienting effects were defined by lower reaction times (RTs) when there was a match between the temporal expectancy for a target (early or late) and the time interval during which the target actually appeared than when they mismatched. Temporal-orienting effects were found for both early and late expectancies with a detection task in Experiment 1. However, catch trials were decisive in whether temporal-orienting effects were observed in the early-expectancy condition. No temporal-orienting effects were found in the discrimination task. In Experiments 2A and 2B, temporal-orienting effects were observed in the discrimination task; however, they were larger when temporal expectancy was manipulated between blocks, rather than within blocks.