Clock time vs. event time: Temporal culture or self-regulation?

Cross-cultural research documented two types of temporal culture governing the way individuals schedule tasks over time: clock-time, where individuals let an external clock dictate when tasks begin/end; and event-time, where tasks are planned relative to other tasks and individuals transition between them when they internally sense that the former task is complete. In contrast with this prior literature - that credits culture as the reason for variation in temporal norms - we show in two experiments that individuals choose clock- vs. event-time as a self-regulation strategy to achieve a regulatory goal (efficiency vs. effectiveness). A third experiment shows that this strategy enhances confidence and performance on a task. Participants solved significantly more math problems when their task scheduling (clock- vs. event-time) matched their regulatory state (promotion vs. prevention). Since clock-/event-time may both lead to superior performance, clock-time is not the single best way to organize productive activities in industrial societies—a result that counters a foundational principle of modern economics.     

Effects of stimulus features and instruction on response coding,selection, and inhibition: Evidence from repetition effects under task switching

The coding of stimuli and responses is crucial for human behaviour. Here, we focused primarily on the response codes (or response categories). As a method, we applied a combined dual-task and task-switch paradigm with a fixed task-to-hand mapping. Usually, negative effects (i.e., costs) are observed for response category repetitions under task switching. However, in several previous studies it has been proposed that such repetition effects do not occur, if the stimulus categories (e.g., “odd” if digits have to be classified according to their parity feature) are unequivocally mapped to specific responses. Our aim was to test this hypothesis. In the present experiments, we were able to distinguish between three different types of possible response codes. The results show that the participants generally code their responses according to abstract response features (left/right, or index/middle finger). Moreover, the spatial codes were preferred over the finger-type codes even if the instructions stressed the latter. This preference, though, seemed to result from a stimulus–response feature overlap, so that the spatial response categories were primed by the respective stimulus features. If there was no such overlap, the instructions determined which type of response code was involved in response selection and inhibition.     

Across-task long-term priming: Interaction of task readiness and automatic retrieval

When humans carry out actions in response to external stimulation, they acquire associations between the stimulus and the action it triggered. When the same stimulus is used in two different tasks, the retrieval of associations compiled in the competing task hampers current performance. Previous research suggests that this across-task priming depends on the task set for the preceding task remaining active across the switch of tasks and, thus, competing with the activations needed for the new task. We present two experiments investigating this notion. Participants switched between two semantic classification tasks. In Experiment 1, participants switched between short runs of the two tasks. Across-task priming was observed on switch and repeat trials. In Experiment 2, participants switched between longer runs of the two tasks. Across-task priming was markedly reduced on repeat trials. The data suggest that whether or not across-task priming affects behaviour after the switch trial depends, amongst others, on whether the task set necessary for the previous task spills into the repeat trials. The implications of these findings for mechanisms of cognitive and mnemonic control are discussed.     

Eye gaze cannot be ignored (but neither can arrows)

Recent studies have shown that switch costs (i.e., slower responding on task-alternation trials than on task-repetition trials) are not observed when on the preceding trial a no-go signal instructed the participant to withhold the response to the target stimulus. This finding suggests that neither task set is inhibited on no-go trials, and that the origin of switch costs is located in the application of the task set to the target stimulus. However, these studies also showed that responding after a no-go trial is substantially slower than after a go trial. This suggests that both task sets are inhibited on no-go trials and that switch costs originate from the preparation of a task set. In two experiments we created conditions that revealed an absence of switch costs in conjunction with relatively fast responding after no-go trials. Together these findings confirm that switch costs originate from the application of the task set.     

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.     

Extreme elemental processing in a high schizotypy population: Relation to cognitive deficits

The cognitive deficits observed in schizophrenia have been characterized as a failure to utilize task-setting information to guide behaviour, especially in situations in which there is response conflict. Recently, we have provided support for this account; high schizotypy individuals demonstrated inferior biconditional discrimination performance compared to low scorers, but were not impaired on a simple discrimination that did not require the use of task-setting cues. These results may, however, also be explained by the way in which individuals with high schizotypy process stimulus compounds. Here, we examine the initial approaches to solving biconditional and control discrimination tasks of participants with high and low schizotypy scores. In particular, we focus on performance during the first block of training trials to capture processing style before the acquisition of the discrimination tasks. Participants scoring highly on the introvertive anhedonia subscale (which has been allied to the negative and cognitive symptoms of schizophrenia) demonstrated better biconditional performance during the first block of training trials than did low-schizotypy individuals, consistent with a highly elemental approach to stimulus processing. Subsequent recognition tests confirmed this analysis demonstrating that the pattern of performance observed in participants with high schizotypy was associated with a failure to discriminate conjunctions of items that had been seen before from those that had not. These results suggest that the negative/cognitive symptoms of schizophrenia may reflect an extreme bias towards elemental, as opposed to configural, processing of stimulus conjunctions.     

Rethinking volitional control over task choice in multitask environments: Use of a stimulus set selection strategy in voluntary task switching

Under conditions of volitional control in multitask environments, subjects may engage in a variety of strategies to guide task selection. The current research examines whether subjects may sometimes use a top-down control strategy of selecting a task-irrelevant stimulus dimension, such as location, to guide task selection. We term this approach a stimulus set selection strategy. Using a voluntary task switching procedure, subjects voluntarily switched between categorizing letter and number stimuli that appeared in two, four, or eight possible target locations. Effects of stimulus availability, manipulated by varying the stimulus onset asynchrony between the two target stimuli, and location repetition were analysed to assess the use of a stimulus set selection strategy. Considered across position condition, Experiment 1 showed effects of both stimulus availability and location repetition on task choice suggesting that only in the 2-position condition, where selection based on location always results in a target at the selected location, subjects may have been using a stimulus set selection strategy on some trials. Experiment 2 replicated and extended these findings in a visually more cluttered environment. These results indicate that, contrary to current models of task selection in voluntary task switching, the top-down control of task selection may occur in the absence of the formation of an intention to perform a particular task.     

A dissociation between the sense of familiarity and access to semantic information concerning familiar people

In the current study we examined the relationship between working memory capacity, inhibition/susceptibility to interference and fluid intelligence, measured by the Raven's Progressive Matrices (PM38), comparing groups of young (aged 18–35), young-old (aged 65–74), and old-old (aged 75–86) participants. Groups were administered two working memory tasks tapping into different mechanisms involved in working memory. The ability to control for irrelevant information was measured both considering memory errors (intrusion errors) in a working memory task and an index of susceptibility to interference obtained with a variant of the Brown-Peterson task. Regression analyses showed that the classical working memory measure was the most potent predictors of the Raven's score. Susceptibility to interference and intrusions errors contributed, but to a lower extent, to the Raven explained variance. These results confirm that working memory shares cognitive aspects with the fluid intelligence measure considered, whereas the role of inhibition to Raven scores is still in need of better evidence.