Is conflict adaptation due to active regulation or passive carry-over? Evidence from eye movements.

Conflict-adaptation effects (i.e., reduced response-time costs on high-conflict trials following high-conflict trials) supposedly represent our cognitive system's ability to regulate itself according to current processing demands. However, currently it is not clear whether these effects reflect conflict-triggered, active regulation, or passive carry-over of previous-trial control settings. We used eye movements to examine whether the degree of experienced conflict modulates conflict-adaptation effects, as the conflict-triggered regulation view predicts. Across 2 experiments in which participants had to identify a target stimulus based on an endogenous cue while-on conflict trials-having to resist a sudden-onset distractor, we found a clear indication of conflict adaptation. This adaptation effect disappeared however, when participants inadvertently fixated the sudden-onset distractor on the previous trial-that is, when they experienced a high degree of conflict. This pattern of results suggests that conflict adaptation can be explained parsimoniously in terms of a broader memory process that retains recently adopted control settings across trials. (PsycINFO Database Record

Long-term memory and the control of attentional control.

Task-switch costs and in particular the switch-cost asymmetry (i.e., the larger costs of switching to a dominant than a non-dominant task) are usually explained in terms of trial-to-trial carry-over of task-specific control settings. Here we argue that task switches are just one example of situations that trigger a transition from working-memory maintenance to updating, thereby opening working memory to interference from long-term memory. We used a new paradigm that requires selecting a spatial location either on the basis of a central cue (i.e., endogenous control of attention) or a peripheral, sudden onset (i.e., exogenous control of attention). We found a strong cost asymmetry that occurred even after short interruptions of otherwise single-task blocks (Exp. 1-3), but that was much stronger when participants had experienced the competing task under conditions of conflict (Exp. 1-2). Experiment 3 showed that the asymmetric costs were due to interruptions per se, rather than to associative interference tied to specific interruption activities. Experiment 4 generalized the basic pattern across interruptions varying in length or control demands and Experiment 5 across primary tasks with response-selection conflict rather than attentional conflict. Combined, the results support a model in which costs of selecting control settings arise when (a) potentially interfering memory traces have been encoded in long-term memory and (b) working-memory is forced from a maintenance mode into an updating mode (e.g., through task interruptions), thereby allowing unwanted retrieval of the encoded memory traces.

Eye movements reveal dynamics of task control.

With the goal to determine the cognitive architecture that underlies flexible changes of control settings, we assessed within-trial and across-trial dynamics of attentional selection by tracking of eye movements in the context of a cued task-switching paradigm. Within-trial dynamics revealed a switch-induced, discrete delay in onset of task-congruent fixations, a result that is consistent with a higher level configuration process. Next, we derived predictions about the trial-to-trial dynamic coupling of control settings from competing models, assuming that control is achieved either through task-level competition or through higher level configuration processes. Empirical coupling dynamics between trial n-1 eye movements and trial n response times--estimated through mixed linear modeling--revealed a pattern that was consistent with the higher level configuration model. The results indicate that a combination of eye movement data and mixed modeling methods can yield new constraints on models of flexible control. This general approach can be useful in any domain in which theoretical progress depends on high-resolution information about dynamic relationships within individuals.

The case for the physician assistant.

The NHS is facing a crisis from the combination of EWTD, MMC, the ageing population and rising expectations; thus its tradition of high quality care is under pressure. Physician assistants (PAs) are a new profession to the UK, educated to nationally set standards and, working as dependent practitioners, provide care in the medical model. PAs are currently employed by over 20 hospital Trusts as well as in primary care. They offer greater continuity than locum doctors and at considerably lower cost. PAs maintain generic competence and can therefore be utilised as required across different clinical areas. The stability of PAs in the workforce will be an additional resource for junior doctors on brief rotations. For the full benefits of PAs to be realised, and for the safety of the public, statutory registration and prescribing rights are required. Active support from the NHS is now needed to develop the workforce required.

Competitiveness across the life span: the feisty fifties.

Existing theories on life span changes in confidence or motivation suggest that individuals' preferences to enter competitive situations should gradually decline with age. We examined competitive preferences in a field experiment using real financial stakes in 25- to 75-year-olds (N = 543). The critical dependent variable was whether participants chose to perform a simple mental arithmetic task either under a piece-rate payment schedule (i.e., $.25 per solved item) or a competitive payment schedule ($.50 per solved item if the overall score is better than that of a randomly selected opponent, $0 otherwise). Results revealed that competitive preferences increased across the life span until they peaked around age 50, and dropped thereafter. We also found that throughout, men had a substantially larger preference for competing than women-extending previous findings on college-aged participants. The age/gender differences in preferences were neither accounted for by actual differences in performance nor individuals' subjective confidence. This first systematic attempt to characterize age differences in competitive behavior suggests that a simple decline conception of competitiveness needs to be reconsidered.

Age-related differences in switching between cognitive tasks: does internal control ability decline with age?

The present study tested the hypothesis that older adults establish a weaker task set than younger adults and therefore rely more on stimulus-triggered activation of task sets. This hypothesis predicts that older adults should have difficulty with task switches, especially when the stimuli-responses are associated with multiple, competing tasks. Weak task preparation, however, could actually benefit older adults when performing an unexpected task. The authors tested this prediction in Experiment 1 using a repeating AABB task sequence, with univalent and bivalent stimuli intermixed. On some univalent trials, participants received an unexpected task. Contrary to the authors' predictions, expectancy costs were not smaller for older adults. Similar findings were obtained in Experiments 2 and 3, in which the authors used a task-cueing paradigm to more strongly promote deliberate task preparation. The authors found no disproportionate age effects on switch costs but did find age effects on bivalence costs and mixing costs. The authors conclude that older adults do experience extra difficulty dealing with stimuli associated with 2 active tasks but found no evidence that the problem specifically stems from an increased reliance on bottom-up task activation rather than top-down task preparation.

Proactive versus reactive task-set inhibition: evidence from flanker compatibility effects.

Two converging tests were used to determine whether people proactively inhibit recently performed tasks when switching to new tasks. A task-cuing paradigm was used. In each trial, the relevant stimulus was accompanied by flankers belonging either to the task performed on the immediately preceding trial (lag 1) or a more distant trial (lag 2 +). If the just-performed task is inhibited when switching to another task, and this inhibition declines across trials, then flanker interference should be smaller with lag 1 flankers than with lag 2 + flankers. Experiment 1, following the methods of Hübner, Dreisbach, Haider, and Kluwe (2003), failed to confirm this prediction. The prediction was confirmed in Experiment 2, however, using a design modified to provide greater incentives for task-set inhibition. The results provide evidence that inhibition can be applied proactively, to reduce the ability of an abandoned task to interfere with the performance of other tasks.

On the difficulty of task switching: assessing the role of task-set inhibition.

This study assessed whether or not the difficulty of task switching stems from previous inhibition of the task set. A predictable sequence of univalent stimuli (affording performance of one active task) and bivalent stimuli (affording performance of two tasks) was used in two experiments. Experiment 1 used an alternating-runs paradigm (AABB) and Experiment 2 used a strictly alternating sequence (ABAB). The critical variable was whether the incentive for task-set inhibition was strong (on bivalent trials) or weak (on univalent trials). The question was whether it would be more difficult to switch to a task that previously needed to be inhibited than to a task that did not need to be inhibited. This pattern was not observed in either experiment. Thus, the data provide no evidence that task switching is difficult because of the need to overcome recent task-set inhibition.

Globalizing the PA profession.

US physician assistants (PAs) have long been working in other parts of the world. Recently, several countries in Western Europe have begun to investigate whether the PA concept can help their own predicted health provider shortages. The author, who was the first PA to work internationally with the humanitarian group Doctors Without Borders, reviews the current status of PAs around the world and identifies the emerging issues, obstacles, and opportunities associated with globalizing the profession.