Task Overlap Research Articles

Dual-task processing in younger and older adults: Similarities and differences revealed by fMRI

fMRI was used to explore age differences in the neural substrate of dual-task processing. Brain activations when there was a 100ms SOA between tasks, and task overlap was high, were contrasted with activations when there was a 1000ms SOA, and first task processing was largely complete before the second task began. Younger adults (M=21yrs) showed activation in dorsolateral prefrontal cortex and in parietal areas as well as in ventral medial frontal cortex and sub-lobar areas. Activations in older adults (M=71yrs) did not differ significantly from younger adults except for higher activations in occipital and polar prefrontal cortex. The results were well fit by a model with two networks managing dual-task interference, a medial prefrontal network that detects changes in the stimulus situation and maps them to associated changes in the valence of response mappings and a lateral frontal–parietal network that initiates and carries out the shift from one task to the other. The additional activations in older adults as a group and the correlations of individual differences in activation with performance were consistent with recruitment within each of these networks. Alternative explanations such as hemispheric asymmetry reduction and reactive rather than proactive processing in older adults were not supported.

Differential dynamics of spatial and non-spatial stimulus-response compatibility effects: A dual task LRP study

Choice reaction times are shorter when stimulus and response features are compatible rather than incompatible. Recent studies revealed that spatial compatibility effects in Simon tasks are strongly attenuated when there is temporal overlap with a different high-priority task. In contrast, non-spatial variants of the Simon task appear to be unaffected by task overlap. The present study used the lateralized readiness potential (LRP) within a dual task design to elucidate the dynamics underlying these differential effects for a color and a spatial variant of the Simon task. In the color version there was no sign of early response priming by irrelevant stimulus features in the LRP. The color compatibility effect was independent of task overlap and reflected in the LRP onset latency. In contrast, in the spatial version, priming by irrelevant stimulus location showed up and was mirrored by early LRP activation. Response priming and the corresponding Simon effect, however, were present only in case of little temporal overlap with the primary task. The absence of spatial compatibility effects at strong temporal overlap suggests that response conflicts due to stimulus-related priming depend on the availability of processing resources.

Crossmodal action selection: Evidence from dual-task compatibility

Response-related mechanisms of multitasking were studied by analyzing simultaneous processing of responses in different modalities (i.e., crossmodal action). Participants responded to a single auditory stimulus with a saccade, a manual response (single-task conditions), or both (dual-task condition). We used a spatially incompatible stimulus-response mapping for one task, but not for the other. Critically, inverting these mappings varied temporal task overlap in dual-task conditions while keeping spatial incompatibility across responses constant. Unlike previous paradigms, temporal task overlap was manipulated without utilizing sequential stimulus presentation, which might induce strategic serial processing. The results revealed dual-task costs, but these were not affected by an increase of temporal task overlap. This finding is evidence for parallel response selection in multitasking. We propose that crossmodal action is processed by a central mapping-selection mechanism in working memory and that the dual-task costs are mainly caused by mapping-related crosstalk.

Problem-Solving Base Building under Uncertainty and Ambiguity: Multiple-Case Study on an Airport Expansion Program

This multiple-case study induces alternative strategies to coordinate the overlap of tasks to detail and physically execute base building with tasks to conceptualize the business-critical fit out. Base-building subsystems provide service space for occupancy, whereas fit-out subsystems make the space functional. Our empirical findings on problem-solving base-building design under uncertainty and ambiguity stem from a number of projects in an airport expansion program. They suggest that base-building subsystems show low sensitivity to incremental changes in fit out as their definitions are seldom optimized to eliminate slack. Yet, base-building subsystems show high sensitivity to radical changes in fit out when the architectures of the two subsystems are integral to one another. Three strategies for problem-solving base building stand out: (1) iterate design when preliminary information about fit out is ambiguous, or precise but unstable; (2) physically decouple the architectures of base building and fit out; and (3) design buffers in base building when preliminary information about fit out lacks precision but it is not ambiguous. These buffers can be designed out if uncertainties in fit out resolve favorably before starting the physical execution for base building.

Is lexical access autonomous? Evidence from combining overlapping tasks with recording event-related brain potentials

In order to test the frequent assumption that lexical access in visual word recognition would proceed independent of central attention, the overlapping task paradigm has recently been employed with somewhat contradictory results. Here we combined overlapping tasks with the recording of event-related brain potentials to assess task load dependent modulations of lexical access in more detail. The study was carried out in Spanish with native Spanish speaking participants. They performed a high-priority pitch discrimination task followed by a visual lexical decision task, in which the difficulty of lexical access was manipulated by means of word frequency. Increasing task load by reducing the stimulus onset asynchrony between both tasks from 700 to 100 ms resulted in considerable slowing of lexical decisions. Word frequency effects were underadditive with the slowing induced by task overlap, indicating lexical access to take place although central attention was dedicated to the high-priority task. The effect of word frequency on the event-related potentials, used as electrophysiological indicator of lexical access, was much less delayed than the lexical decision responses in conditions of high task overlap, providing converging evidence for the independence of lexical access from central attention. On the other hand, this slight delay and an amplitude reduction of the effect with high task load show that lexical access may not be completely autonomous, but subject to some additional early source of interference.

Cross-modal multitasking processing deficits prior to the central bottleneck revealed by event-related potentials

We investigated whether concurrent processing of a tone (T1) interferes with early sensory-perceptual processing of a visual target (T2) in variants of the psychological refractory period paradigm using the event-related potential (ERP) method and 70-channel electroencephalographic recordings. T1, which required a speeded response, was presented in all trials. In half of the trials, T1 was followed by a bilateral visual display, T2, which also required a speeded response. A single T1–T2 stimulus onset asynchrony was adjusted dynamically to maximize task overlap in a hard-Task1 condition while minimizing task overlap in an easy-Task1 condition. The ERP to T1 in trials with only T1 presented (uncontaminated by T2) enabled us to subtract T1-related activity from the dual-task T2-locked ERPs. An attenuation of the T2-locked occipital N1 was observed in the hard-Task1 condition, relative to the easy-Task1 condition, both when T2 required a discriminative response and a detection response. An attenuation of the visual P1 component was also observed when T2 required a discriminative response. The N2pc was also attenuated, and the sustained posterior contralateral negativity (SPCN) was delayed, by concurrent processing in the discrimination task. Implications for models of dual-task interference are discussed.

PRACTITIONER APPLICATION: Task Overlap Among Primary Care Team Members: An Opportunity for System Redesign?

PRACTITIONER APPLICATION: Task Overlap Among Primary Care Team Members: An Opportunity for System Redesign?

Task Overlap Among Primary Care Team Members: An Opportunity for System Redesign?

This article presents the results of research on a systematic approach to the assignment of primary care work in the Veterans Health Administration. Based on a functional job analysis protocol, the study identified overlap in the performance of primary care tasks among multiple occupational groups as prima facie evidence of opportunities to reallocate work responsibilities. Results show that registered nurses, physicians, advanced practitioners, and licensed vocational nurses reported performing 60 percent to 97 percent of the same tasks, while clerks and health technicians appeared to be underutilized. The frequency and duration with which occupational groups performed each task were also examined, providing additional evidence to be used in improving clinic efficiency. The management of healthcare personnel can be improved through systematic analysis of the work, the worker, and the work organization and through more informed decisions about the appropriateness of task assignment (or reassignment). This article presents an evidence-based approach to personnel management with important implications for clinic efficiency. The approach can be used to guide strategic planning and staffing decisions by identifying not only who currently does the work but, more importantly, who should be doing the work given the full array of data.

Nursing time allocation and other considerations for staffing

The purpose of this project was to evaluate how nursing staff on the telemetry unit at Merle West Medical Center, a rural Pacific northwest community medical center in the USA, spend their time on selected nursing tasks, and how they believed staffing and patient acuity levels could best be determined. A self-report survey tool was developed, piloted and administered. Of the tasks that were listed in the survey, registered nurses (RNs) reported spending 39% of their time performing tasks that RNs only can perform. RNs reported spending 12% of their time performing activities that certified nursing assistants (CNAs) could perform alone and 49% of their time was spent on tasks that both RNs and CNAs must perform. Results from the quantitative portion of the survey indicated that RNs may not be used efficiently due to task overlap. Administering a modified survey which includes a balance of direct and indirect patient care tasks, as well as only those tasks that are truly performed frequently, will increase the relevance of the results.

Stimulus-related priming during task switching.

Task switch cost (the deficit of performing a new task vs. a repeated task) has been partly attributed to priming of the repeated task, as well as to inappropriate preparation for the switched task. In the present study, we examined the nature of the priming effect by repeating stimulus-related processes, such as stimulus encoding or stimulus identification. We adopted a partial-overlap task-switching paradigm, in which only stimulus-related processes should be repeated or switched. The switch cost in this partial-overlap condition was smaller than the cost in the full-overlap condition, in which the task overlap involved more than stimulus processing, indicating that priming of a stimulus is a component of a switch cost. The switch cost in the partial-overlap condition, however, disappeared eventually with a long interval between two tasks, whereas the cost in the full-overlap condition remained significant. Moreover, the switch cost, in general, did not interact with foreknowledge, suggesting that preparation on the basis of foreknowledge may be related to processes beyond stimulus encoding. These results suggest that stimulus-related priming is automatic and short-lived and, therefore, is not a part of the persisting portion of switch cost.

Cued shifts of attention and memory encoding in partial report: a dual-task approach.

This study explores how cued shifts of visual attention and rapid encoding of visual information relate to limited-capacity processing mechanisms. Three experiments were conducted placing a partial-report task within a dual-task paradigm. Experiments 1 and 2 involved a simple speeded visual discrimination (Task 1) and then an unspeeded partial-report task (Task 2). Generally, Task 2 accuracy declined as the temporal overlap between the two tasks increased. In addition, in Experiment 1, varying the number of items in the partial-report display had an effect on performance regardless of overlap. In contrast, in Experiment 2, varying the type of probe had an effect only at long task overlap. The generality of the interference effect was tested in Experiment 3 using an auditory discrimination as Task 1. Again, Task 2 accuracy declined as the temporal overlap between the two tasks increased. In all cases, the observed interference had the properties of a processing bottleneck. It is argued that encoding information into memory and response selection for the first task both require general-purpose processing. The results are discussed in terms of the functional relationship between attention and memory.

Supervising Paraprofessionals

This study examined the practices of special education teachers with responsibility for the supervision of paraprofessionals. Teachers reported little preservice or inservice preparation for supervising; "real-life experience" was the primary source of their supervision knowledge. Few teachers participated in selecting or hiring the paraprofessional they supervised, although more than half of the respondents indicated that they held primary responsibility for evaluating the performance of paraprofessionals. Teachers provided oral instructions to paraprofessionals rather than written plans. The oral instructions consisted of directions about guiding students' skills practice and suggestions for behavior management. Few teachers held regularly scheduled, sit-down meetings with paraprofessionals. Substantial overlap of tasks and duties was reported. However, paraprofessionals assumed primary responsibility for the personal care of students and for playground supervision. Teachers maintained primary responsibility for determining goals and objectives of the Individualized Education Program (IEP), informing parents, attending IEP meetings, and planning lessons. The remaining tasks, including many involving instruction, were equally shared. Findings demonstrated that teachers' supervision methods vary somewhat from recommended supervisory practices and support the call for supervisory training in preservice and inservice special education programs.

Functional MRI Study of Posterior Parietal Cortex in Visuomotor Tasks

The posterior parietal cortex is known to be involved in visuomotor task processing. Unsolved question are 1) whether a special cortical network is implied in pointing tasks or the same network is shared by other tasks with similar visual input and motor output 2) is there a hemispheric specialization in these treatments? Axial MR images were acquired in eight right-handed volunteers, using EPI sequence. Behavioral conditions were designed to perform two visiomotor tasks: a) pointing to a visual target, with the right or left hand; b) spatial detection of the visual target. Both tasks shared the same retinal input and motor output. The visual stimuli were generated by a computer and projected on a screen. Data processing included conditioned analysis and inter-subject comparison of different task activation extent and overlap in different cortical regions. Both tasks activated the same fronto-parietal network. Within this network, there was a significant cortical activation overlap between the pointing ta...

The effects of stimulus–response mapping and irrelevant stimulus–response and stimulus–stimulus overlap in four-choice Stroop tasks with single-carrier stimuli.

The effects of stimulus–response mapping and irrelevant stimulus–response and stimulus–stimulus overlap in four-choice Stroop tasks with single-carrier stimuli.

Merging Family and Firm: An Integrated Systems Approach to Process and Change

The blurring of family and business in family businesses can create tremendous stress for all family members. Scholars have been unsuccessful in applying task-oriented, business-based models to a business in which the boundaries between task and family blur and overlap. This article integrates current research and theory related to family interaction, organizational dynamics, and family businesses to present a conceptual framework that details the complex inner workings of family businesses and helps guide those who study and work with them.

Multiple spatial codes and temporal overlap in choice-reaction tasks

Experiments by Umilta and Liotti (1987) and Lamberts, Tavernier, & d'Ydewalle (1992) examined the Simon effect (an influence of irrelevant stimulus location on reaction time) as a function of multiple frames of reference. The Simon effect was absent for all reference frames in the former experiment, leading Stoffer (1991) to propose that a spatial code is formed only if the last step in directing attention to the imperative stimulus is a lateral shift. However, the Simon effect was evident for all frames in the latter experiment. Hommel (1994) proposed that the multiple spatial codes implied by Lamberts et al.'s findings were also activated in Umilta and Liotti's experiment but had decayed by the time the relevant stimulus information had been identified. Experiments 1, 2, and 3 examined these accounts of attention shifting, multiple codes, and temporal overlap for variations of the Simon task in which the stimulus could occur in one of either eight or four possible stimulus locations. Three stimulus sets that differed in ease of discriminability were used in each experiment. Experiments 1 and 2 were replications and extensions of those of Lamberts et al. and Umilta and Liotti, respectively. In both experiments, two boxes, with a stimulus inside of one, appeared simultaneously, and the subject was to respond to the identity of the stimulus. Experiment 3 used a procedure in which the four stimulus locations were demarcated by three vertical lines. Two of the three experiments showed Simon effects with respect to multiple frames of reference, and the magnitude of these effects was a decreasing function of the difficulty of stimulus discriminability. Spatial compatibility proper was examined in Experiment 4 using the same layout as Experiment 3. In this case, only the relevant frame of reference was coded. On the whole, the results indicate that multiple codes are formed, but not automatically, and that those codes decay when irrelevant.

Phonological priming between monosyllabic spoken words.

Phonological priming between 3-phoneme monosyllabic spoken words was examined as a function of the early or late position of the phonological overlap between the words and of prime-target relative frequency. The pairs of words had either the 2 beginning or the 2 final phonemes in common. Four experiments were conducted, each using a different combination of interstimulus interval (ISI; either 20 ms or 500 ms) and task (either lexical decision or shadowing). Facilitation was consistently found between words with final overlap in both tasks and was not affected by either absolute or relative word frequency. The size of the effect decreased as the ISI increased. Significant priming effects were not obtained between words with initial overlap, although an inhibitory trend was found in the shadowing task at the short ISI for the low-high relative frequency condition. It is suggested that the facilitatory effect of final overlap is prelexical.

Can mental rotation occur before the dual-task bottleneck?

The effect of character disorientation on mirror-normal judgments was found to be partially attenuated with increasing task overlap with a preceding tone-frequency discrimination judgment. These results suggest that orientation-sensitive processing, used to prepare disoriented stimuli for mirror-normal discrimination, can be initiated and proceed in parallel with mental activities required for a tone-frequency discrimination task. The attenuation indicates that at least some of the orientation effect on mirror-normal discriminations has its locus prior to the dual-task processing bottleneck. The possibility that the partial attenuation of the orientation effect was due to attenuation of the effect of orientation on character identification, but not on the mental rotation required for mirror-normal judgments, was examined and rejected.

The Emergence of the Paraprofessional in Academic Libraries: Perceptions and Realities

Several forces have contributed to a broad redistribution of tasks within the library workplace. Today, support staff accomplish much of the day-to-day work of the library and are routinely assigned tasks that a generation ago characterized the work of librarians. This redistribution of the library work load has created a new and unique class of library worker, the paraprofessional. It has also resulted in a significant overlap in the tasks performed by the two groups, for librarians have been curiously reluctant to give up many traditional aspects of their work that today can be performed satisfactorily by paraprofessionals. Task overlap has caused the role blurring that, in turn, creates resentment in the workplace and confuses our clientele who may not distinguish clearly between the two groups.A new model of librarianship is needed to define less ambiguously the role of paraprofessionals and librarians alike

Locus of the single-channel bottleneck in dual-task interference.

Two experiments used the locus-of-cognitive-slack method to determine whether dual-task interference occurs before or after the response selection stage. The experiments used the overlapping tasks paradigm, in which two signals, each requiring a different speeded choice response, are presented in rapid succession. In Experiment 1, stimulus-response (S-R) compatibility was manipulated by varying whether Task 2 stimuli were mapped onto their responses by a rule or arbitrarily. Compatibility effects were additive with the effects of degree of task overlap, manipulated by varying the stimulus onset asynchrony between the signals. Experiment 2 examined 2 additional forms of S-R compatibility: symbolic compatability (arrows vs. letters) and spatial compatibility (the 'Simon' effect). Effects of symbolic compatibility were additive with effects of degree of task overlap, whereas the effects of spatial compatibility and degree of task overlap were underadditive. It is argued that only a central-bottleneck model provides a consistent account of these results. The nature of the central bottleneck is considered.