Positive affect facilitates task switching in the dimensional change card sort task: Implications for the shifting aspect of executive function

Using the modified Dimensional Change Card Sort task, we examined the influence of positive affect on task switching by inspecting various markers for the costs, including restart cost, switch cost and mixing cost. Given that the executive-control processes that underlie switching performance—i.e., inhibition or shifting—are distinct from the component processes that underlie non-switching performance—i.e., stimulus evaluation, resource allocation or response execution—we hypothesised that if positive affect facilitates task switching via executive-control processes, rather than via component processes, positive affect would reduce both switch and restart costs, but not mixing cost, because both switch and restart costs rely on executive processes, while mixing cost imposes only minimal demands on executive processes. We found beneficial effects of positive affect on both restart and switch costs, but not on mixing costs. These results suggest that positive affect improves switching abilities via executive processes rather than via component processes.     

Impaired task switching performance in children with dyslexia but not in children with autism

Problems with cognitive control in both autism and dyslexia have already been reported in different studies. The present study specifically examined task-switching performance in children with autism and dyslexia. For this purpose, a multiple-trial paradigm was used with cues for colour- and shape-matching tasks presented before a run of trials. The cue could imply a task switch (when the cue changed the task) or a task repetition (when the cue did not change the task). Both reaction times and error rates were measured for switching, restarting, and general task performance. Participants were children with autism (24) and with dyslexia (25) and healthy controls (27) with normal IQ and ages from 12 to 18 years. The main finding was that while similar switching performance was observed between children with autism and the healthy controls, children with dyslexia showed a significant switch-specific delay relative to both healthy controls and children with autism. Furthermore, no deficit in restarting performance was observed for any of the two patient groups. Finally, additional evidence is provided for a more general deficit in information processing in dyslexia. Our data suggest that children with autism are able to switch between tasks in a similar way as do normally developing children as long as the tasks are unambiguously specified. Furthermore, the data imply switch-specific deficits in dyslexia additionally to the deficits in general information processing already reported in the literature. The implications of our data are further discussed in relation to the interpretation of the Wisconsin Card Sorting Test.     

Intentional attention switching in dichotic listening: Exploring the efficiency of nonspatial and spatial selection

Using an auditory variant of task switching, we examined the ability to intentionally switch attention in a dichotic-listening task. In our study, participants responded selectively to one of two simultaneously presented auditory number words (spoken by a female and a male, one for each ear) by categorizing its numerical magnitude. The mapping of gender (female vs. male) and ear (left vs. right) was unpredictable. The to-be-attended feature for gender or ear, respectively, was indicated by a visual selection cue prior to auditory stimulus onset. In Experiment 1, explicitly cued switches of the relevant feature dimension (e.g., from gender to ear) and switches of the relevant feature within a dimension (e.g., from male to female) occurred in an unpredictable manner. We found large performance costs when the relevant feature switched, but switches of the relevant feature dimension incurred only small additional costs. The feature-switch costs were larger in ear-relevant than in gender-relevant trials. In Experiment 2, we replicated these findings using a simplified design (i.e., only within-dimension switches with blocked dimensions). In Experiment 3, we examined preparation effects by manipulating the cueing interval and found a preparation benefit only when ear was cued. Together, our data suggest that the large part of attentional switch costs arises from reconfiguration at the level of relevant auditory features (e.g., left vs. right) rather than feature dimensions (ear vs. gender). Additionally, our findings suggest that ear-based target selection benefits more from preparation time (i.e., time to direct attention to one ear) than gender-based target selection.     

Preparing or executing the wrong task: The influence on switch effects

In a previous study, it was proposed that executing a task leads to task strengthening. In other words, task activation at the moment of response execution determines subsequent switch effects (Steinhauser & Hübner, 2006). The authors investigated this issue by comparing switch effects after task and response errors. However, the use of bivalent stimulus–response mappings might have obscured some of the effects. Therefore, we replicated the experiment using univalent stimulus–response mappings. With this adjusted design, which overcomes some shortcomings of the original study, we were able to replicate the finding of switch benefits after task errors. Closer inspection of the data showed the importance of preexecution processes on subsequent switch effects. In a second experiment, we further elaborated on these preexecution processes. More precisely, we investigated the effect of task preparation on subsequent switch effects. Taken together, our data extend current accounts of task switching by showing that the preparatory processes occurring before the response on trial n influence the switch cost on trial n?+?1.     

Attentional orienting across the sensory modalities

This event-related potential study investigated (i) to what extent incongruence between attention-directing cue and cued target modality affects attentional control processes that bias the system in advance to favor a particular stimulus modality and (ii) to what extent top-down attentional control mechanisms are generalized for the type of information that is to be attended. To this end, both visual and auditory word cues were used to instruct participants to direct attention to a specific visual (color) or auditory (pitch) stimulus feature of a forthcoming multisensory target stimulus. Effects of cue congruency were observed within 200 ms post-cue over frontal scalp regions and related to processes involved in shifting attention from the cue modality to the modality of the task-relevant target feature. Both directing visual attention and directing auditory attention were associated with dorsal posterior positivity, followed by sustained fronto-central negativity. However, this fronto-central negativity appeared to have an earlier onset and was more pronounced when the visual modality was cued. Together the present results suggest that the mechanisms involved in deploying attention are to some extent determined by the modality (visual, auditory) in which attention operates, and in addition, that some of these mechanisms can also be affected by cue congruency.     

The costs of crossing paths and switching tasks between audition and vision

Switching from one functional or cognitive operation to another is thought to rely on executive/control processes. The efficacy of these processes may depend on the extent of overlap between neural circuitry mediating the different tasks; more effective task preparation (and by extension smaller switch costs) is achieved when this overlap is small. We investigated the performance costs associated with switching tasks and/or switching sensory modalities. Participants discriminated either the identity or spatial location of objects that were presented either visually or acoustically. Switch costs between tasks were significantly smaller when the sensory modality of the task switched versus when it repeated. This was the case irrespective of whether the pre-trial cue informed participants only of the upcoming task, but not sensory modality (Experiment 1) or whether the pre-trial cue was informative about both the upcoming task and sensory modality (Experiment 2). In addition, in both experiments switch costs between the senses were positively correlated when the sensory modality of the task repeated across trials and not when it switched. The collective evidence supports the independence of control processes mediating task switching and modality switching and also the hypothesis that switch costs reflect competitive interference between neural circuits.     

Adjustments of task-set control processes: Effect of task switch frequency on task-mixing and task-switching costs

The present study tested the hypothesis that task-switch frequency triggers adjustments of task-set control processes. A mixed-task condition where task switches are frequent should promote flexibility—thus improving task-switch performance—whereas a condition where task repetitions are more expected should favour stability—thus improving task-repeat performance. In two experiments, participants performed single-task and mixed-task blocks. In mixed-task blocks, tasks varied randomly on a trial-by-trial basis. For half of the mixed-task blocks, the frequency with which the task changed was 25%, for the other half, it was 50%. Overall, depending on the task-switch frequency, performance on both task-repeat and task-switch trials was modified. Switch cost was reduced and task-repeat performance was altered by the increase in switch probability. This study demonstrates context-sensitive adjustments of task-set control processes. These results further support the view that mixing cost reflects sustained and endogenous components of cognitive control.     

Effects of mixing and cueing simple addition and multiplication

Miller and Paredes (1990) found that both children's and adults' performance of simple addition and multiplication tested in mixed-operation blocks was slower and more susceptible to operation errors (e.g., 6 + 2=12 or 6×2=8) compared to pure-operation blocks; but mixed-operation costs were greater for addition than for multiplication. We pursued the source of these effects in adults (n=96) by examining effects of operation switching and cueing. We replicated the asymmetrical costs of mixing addition and multiplication and demonstrated that these owed, in part, to asymmetrical task switching costs. Operation foreknowledge (a visual cue appearing 2 s before the problem) moderated both mixing and switch costs. This suggests that an asymmetry between addition and multiplication in the utility of preparation contributed to asymmetric mixing costs. Miller and Paredes proposed that the asymmetric costs of mixing operations observed in adults echoed an asymmetry developed in childhood when multiplication is initially learned. This might be correct, but our results raise the possibility that the asymmetry reflects operation-specific costs and interference effects that arise during the experiment.     

Using variability to guide dimensional weighting: associative mechanisms in early word learning

At 14 months, children appear to struggle to apply their fairly well-developed speech perception abilities to learning similar sounding words (e.g., bih/dih; Stager & Werker, 1997). However, variability in nonphonetic aspects of the training stimuli seems to aid word learning at this age. Extant theories of early word learning cannot account for this benefit of variability. We offer a simple explanation for this range of effects based on associative learning. Simulations suggest that if infants encode both noncontrastive information (e.g., cues to speaker voice) and meaningful linguistic cues (e.g., place of articulation or voicing), then associative learning mechanisms predict these variability effects in early word learning. Crucially, this means that despite the importance of task variables in predicting performance, this body of work shows that phonological categories are still developing at this age, and that the structure of noninformative cues has critical influences on word learning abilities.     

How a crisis mindset activates implicit knowledge and brings it into awareness: The role of attentional switch cost

In this study, we relied on the attentional switch cost to ascertain whether a crisis mindset can activate and momentarily bring related implicit knowledge into awareness. We found that the attentional switch cost was higher in a crisis mindset condition than in a common mindset condition in which non-crisis-related stimuli were being attended to (Experiment 1). However, the attentional switch cost was lower in the crisis mindset condition when crisis-related stimuli were being attended to (Experiment 2A), and the reduced cost was not attributable to the complexity of the stimuli (Experiment 2B). A link emerged in the crisis mindset condition between the attentional switch cost and related implicit knowledge (Experiment 3A and 3B). Potential confounding factors were adequately controlled (see the Appendix). In conclusion, the results offer insight into the pivotal role of a crisis mindset. This finding delineates an alternative pathway in which implicit knowledge can be activated and brought into working memory once an event is perceived and interpreted as a crisis.