Conflict tasks are commonly used to investigate control processes under situations of relevant and irrelevant sources of information. In addition to compatibility effects at a mean behavioral level, delta plot analyses of reaction time distributions reveal that the compatibility effect generally increases with time (i.e., positive delta plot slopes) across most conflict-like tasks. Critically, the underlying causes of the increasing delta plot slopes with different types of distractors are still poorly understood. The present study tested whether the relative onset of target-to-distractor processing affects the delta plot slope. Specifically, we manipulated the temporal order of relevant and irrelevant dimensions within an Eriksen flanker task (Experiment [Exp.] 1), an Arrow-Simon task (Exp. 2), and a manual Stroop task (Exp. 3a/3b). The results of the Eriksen flanker task and Arrow-Simon task revealed that the delta plots slopes were less increasing (and instead rather decreasing) when the irrelevant dimension appears first (IR condition) compared to the reversed order (RI condition)-consistent with the idea that the underlying mechanism driving the slope of the delta plot is the temporal overlap of activation between the relevant and irrelevant dimensions. In contrast, for the Stroop task, the delta plots in the RI condition were not more increasing than the ones for the IR condition. Overall, these results suggest that the temporal properties strongly influence delta plot shape, but that the temporal dynamics operating in the flanker task and the Arrow-Simon task differs from the Stroop task, at least under conditions where relevant and irrelevant information is presented sequentially. Public Significance StatementIn many real-world situations, people are required to select and process goal-relevant information in environments overloaded with distracting-and potentially conflicting-sources of information. It is important to uncover the mental control mechanisms that prevent interference allowing successful goaldirected behavior for both practical and theoretical reasons. In the present study, we systematically investigated the temporal processing dynamics with different sources of distracting information. The results indicate that some types of distracting information are similarly processed across time whereas others are not, suggesting the existence of distractor-general and distractor-specific control mechanisms.

Performance is generally worse when performing multiple tasks than when performing a single task, but there is debate about whether this multitasking interference arises due to a structural bottleneck that requires serial central processing or due to resource limitations that slow processing of 2 tasks when they are carried out in parallel. The present study used a novel approach of comparing firstand second-task reaction times (RTs) within the psychological refractory period (PRP) paradigm to contrast these 2 possibilities. Counterbalancing task order across participants to control for differences in task difficulty, we found that second-task responses were faster than first-task responses at long stimulus onset asynchronies (SOAs). This second-task advantage is difficult to explain within bottleneck models, which allow the first task to be processed at full speed while the second task waits for access to the bottleneck process. Instead, the effect suggests that processing of the first task is slowed because some cognitive resources are held back in case they are needed for second-task processing. At long SOAs, all resources can be allocated to second-task processing because the first task is already completed. Thus, we propose that cognitive control processes flexibly coordinating the sharing of limited central resources may better explain dual-task performance in the PRP paradigm than bottleneck-based waiting due to structural limitations. Public Significance StatementIt is well known that the concurrent performance of 2 or more tasks is impaired when compared to performing the tasks separately, but there remains debate about the causes of these multitasking costs. The present findings demonstrate that these costs probably do not emerge from structural bottleneck-type limitations in the human cognitive system that require serial processing of 2 tasks. Instead, the results suggest that these costs arise because the system shares limited cognitive processing resources to process 2 tasks in parallel.

In the present study, we examined how the relevance of potentially distracting information modulates the interplay of target and distractor processing in conflict tasks. Specifically, we manipulated the degree to which distracting information is relevant for performing the overall task by varying the proportion of trials in which a response to the distractor(s) (Experiments 1a and 1b: location in a Simon task; Experiment 2: flankers in an Eriksen flanker task) instead of to the target was required. Across all experiments, the congruency effect on mean RT was larger with the increasing relevance of the distractor(s). Critically, the slopes of the delta plot were more strongly increasing when the distractors were potentially relevant (as opposed to completely irrelevant), suggesting that cognitive control affects the timing of suppressing distractor-based activation. In addition, delta plot and diffusion model analyses revealed that the strength of suppressing distractor processing and the efficiency of target processing were enhanced when the distractors were less relevant. Overall, the present study dissociated multiple and time-dependent adjustments of control processes (i.e., target processing enhancement plus timing and strength of distractor suppression) in environments that encourage either a more stable or more flexible processing mode.

Risk permeates decision making because choice outcomes are often uncertain. When basing decisions on prior experience, previous research suggests that the prospects of gain and loss differentially produce subjective inflation and deflation of risk-associated values, respectively. These effects have been explained in terms of an “extreme-outcome rule”, which posits that valuations of risky options are biased towards the best/worst possible outcome. However, prior studies typically examined risky choices only at the 50% level, and it was unclear whether the risk-preferences predicted by the “extreme outcome rule” would generalize to other probabilities. Furthermore, the cognitive processes underlying risk preferences remained unclear. We addressed these questions through three pre-registered experiments where the critical condition involved decisions between equivaluable safe and risky options across three probabilities (20%, 50%, 80%) with the goals of either maximizing gains or minimizing losses. We found that probability and risk context mutually influenced choice-behavior: low probabilities were particularly subjectively inflated, leading to a strong preference for rare, risky options when seeking gains and a strong aversion when mitigating losses. We also found that decisions involving risk require more cognitive resources, as indicated by longer decision times. Additionally, a risk-sensitive reinforcement model showed that risk-seeking/averse individuals tended to overweight positive/negative outcomes. This study highlights that outcome uncertainty, the range of possible outcomes a given choice option could yield, is a critical component in probability distortion and that subjective probability distortions may drive risk attitudes.

Although humans often multitask, little is known about how the processing of concurrent tasks is managed. The present study investigated whether adjustments in parallel processing during multitasking are local (task-specific) or global (task-unspecific). In three experiments, participants performed one of three tasks: a primary task or, if this task did not require a response, one of two background tasks (i.e., prioritized processing paradigm). To manipulate the degree of parallel processing, we presented blocks consisting mainly of primary or background task trials. In Experiment 1, the frequency manipulation was distributed equally across the two background tasks. In Experiments 2 and 3, only one background task was frequency-biased (inducer task). The other background task was presented equally often in all blocks (diagnostic task) and served to test whether processing adjustments transferred. In all experiments, blocks with frequent background tasks yielded stronger interference between primary and background tasks (primary task performance) and improved background task performance. Thus, resource sharing appeared to increase with high background task probabilities even under triple task requirements. Importantly, these adjustments generalized across the background tasks when they were conceptually and visually similar (Experiment 2). Implementing more distinct background tasks limited the transfer: Adjustments were restricted to the inducer task in background task performance and only small transfer was observed in primary task performance (Experiment 3). Overall, the results indicate that the transfer of adjustments in parallel processing is unrestricted for similar, but limited for distinct tasks, suggesting that task similarity affects the generality of resource allocation in multitasking.