Task switch costs scale with dissimilarity between task rules.

Cognitive flexibility enables humans to voluntarily switch tasks. Task switching requires replacing the previously active task representation with a new one, an operation that typically results in a switch cost. Thus, understanding cognitive flexibility requires understanding how tasks are represented in the brain. We hypothesize that task representations are cognitive map-like, such that the magnitude of the difference between task representations reflects their conceptual differences: The greater the distinction between the two task representations, the more updating is required. This hypothesis predicts that switch costs should increase with between task dissimilarity. To test this hypothesis, we use an experimental design that parametrically manipulates the similarity between task rules. We observe that response time scales with the dissimilarity between the task rules. The findings shed light on the organizational principles of task representations and extend the conventional binary task-switch effect (task repeat vs. switch) to a theoretical framework with parametric task switches. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Comparing partial repetition costs in two- and four-choice tasks: Evidence for abstract relational codes.

Responses are slower in two-choice tasks when either a previous stimulus feature or the previous response repeats than when all features repeat or all features change. Current views of action control posit that such partial repetition costs (PRCs) index the time to update a prior "binding" between a stimulus feature and the response or to resolve processing conflicts between retrieved and current features. However, violating a heuristic that stimulus feature repetitions and changes "signal" repetitions or changes of the previous response, respectively, may also contribute to such costs. To determine whether such relational codes affect performance, we compared PRCs in two- and four-choice tasks. While a stimulus feature repetition signals a response repetition in both tasks, a stimulus feature change signals a specific alternative response only in a two-choice task. Consistent with the signaling hypothesis, we observed similar complete repetition benefits in the two- and four-choice tasks but smaller complete change benefits in the four-choice task. We also investigated whether the smaller complete change benefit in the four-choice task-that is, the signaling effect-varies with the validity of the signal in the previous trial. In all four experiments, we observed a larger signaling effect after trials in which stimulus changes or repetitions corresponded to response changes or repetitions, respectively, than after trials in which stimulus changes did not correspond with response changes. We conclude that signaling contributes to PRCs, which indicates that bindings include relational codes. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Response-repetition costs in task switching do not index a simple response-switch bias: Evidence from manipulating the number of response alternatives.

Response repetitions aid performance when a task repeats but impair performance when a task switches. Although this interaction is robust, theoretical accounts remain controversial. Here, we used an un-cued, predictable task-switching paradigm with univalent targets to explore whether a simple bias to switch the response when the task switches can explain the interaction. In Experiment 1A (n = 40), we replicated the basic interaction in a two-choice task. In Experiment 1B (n = 60), we observed the same interaction in a three-choice task, wherein a bias to switch the response when the task switches cannot prime a specific alternative response because both remaining response alternatives are equally likely. Exploratory comparisons revealed a larger interaction between task repetition and response repetition in the three-choice task than in the two-choice task for mean response time (RT) and the opposite pattern for mean error rate (ER). Critically, in the three-choice task, response-repetition costs in task switches were significant in both RT and ER. Since a bias to switch the response cannot prime a specific response alternative in a three-choice task, we conclude that such a bias cannot account for response-repetition costs in task-switch trials.

Partial repetition costs index a mixture of binding and signaling.

People respond more slowly in two-choice tasks when either a previous stimulus feature or the previous response repeats in partial repetition trials than when (a) both repeat in complete repetition trials or (b) both alternate in complete alternation trials. The binding account posits that such partial repetition costs index a memory-retrieval conflict, which occurs because partial repetition trials trigger the retrieval of a previous stimulus feature or response that conflicts with a current stimulus feature or response. However, such costs may additionally reflect a simple decision-making heuristic that uses the repetition or alternation of a previous stimulus feature as a "signal" to bias response selection toward a repetition or an alternation of the previous response. To determine whether signaling contributes to partial repetition costs, we employed a four-choice task. Here, a stimulus feature repetition still signals a response repetition, but a stimulus feature alternation does not signal which of the three remaining responses to make. Consistent with an influence of signaling, we sometimes observed complete repetition advantages without complete alternation advantages. Exploratory analyses further revealed that partial repetition costs measured more broadly were smaller in the four-choice task than in a matched two-choice task. These findings suggest that partial repetition costs index a mixture of binding and signaling.

Response-repetition costs reflect changes to the representation of an action.

Repeating a response from the previous trial typically leads to performance benefits. However, these benefits are eliminated, and usually reversed, when switching to a new task (i.e., response-repetition costs). Here, we test the proposal that response-repetition costs reflect changes in the representation of an action. To investigate this, we designed tasks that required participants to switch between color and shape judgments with experimentally induced outcomes. Critically, the stimuli and responses were constant across conditions; what differed was the number of outcomes associated with the responses. For both response time and error rate, response-repetition costs on task-switch trials were significantly reduced when response repetitions led to outcome repetitions relative to when response repetitions led to outcome switches. Moreover, response repetitions that led to outcome repetitions showed an advantage in response time (but not error rate) compared with when no outcomes were experimentally induced. We conclude that response-repetition costs reflect a change in the representation of an action and that action selection is largely grounded in the anticipation of the response-related outcomes.

Crosstalk, not resource competition, as a source of dual-task costs: Evidence from manipulating stimulus-action effect conceptual compatibility.

Two related accounts of dual-task costs-multiple resource competition and crosstalk-explain why costs can be reduced when there is less overlap between the two tasks. However, distinguishing between competition for limited resources and crosstalk between concurrently performed operations has proven difficult. In the present study, we compared these two accounts with a dual-task paradigm in which participants were required to coordinate visual-manual and auditory-manual tasks with experimentally induced action effects. Critically, stimulus and response modalities were constant across conditions; what differed was the conceptual relationship between stimuli and action effects such that conceptual overlap was present either within or between tasks. We observed larger dual-task costs when related conceptual codes were present between tasks. We conclude that these results are best supported by the crosstalk account and that postresponse action effects are integrated into task representations engaged by central operations during response selection.

Cue the effects: Stimulus-action effect modality compatibility and dual-task costs.

The pairings of tasks' stimulus and response modalities affect the magnitude of dual-task costs. For example, dual-task costs are larger when a visual-vocal task is paired with an auditory-manual task compared with when a visual-manual task is paired with an auditory-vocal task. These results are often interpreted as reflecting increased crosstalk between central codes for each task. Here we examine a potential source: modality-based crosstalk between the stimuli and the response-induced sensory consequences (i.e., action effects). In five experiments, we manipulated experimentally induced action effects so that they were either modality-compatible or -incompatible with the stimuli. Action effects that were modality-compatible (e.g., visual stimulus, visual action effect) produced smaller dual-task costs than those that were modality-incompatible (e.g., visual stimulus, auditory action effect). Thus, the relationship between stimuli and action effects contributes to dual-task costs. Moreover, modality-compatible pairs showed an advantage compared with when no action effects were experimentally induced. These results add to a growing body of work demonstrating that postresponse sensory events affect response selection processes. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

How conceptual overlap and modality pairings affect task-switching and mixing costs.

Manipulating the pairings of stimulus and response modalities has been shown to affect how response selection processes for distinct tasks interact. For example, Stephan and Koch (Psychol Res 75(6):491-498, 2011) found smaller performance costs when participants switched between visual-manual (VM) and auditory-vocal (AV) tasks (modality compatible; MC) compared to between visual-vocal (VV) and auditory-manual (AM) tasks (modality incompatible; MI). However, in the Stephan and Koch study, there was conceptual overlap between one set of stimuli and one set of responses. For the MC pair, these stimuli and responses belonged to the same task, whereas for the MI pair, they belonged to different tasks. To examine how conceptual overlap affected switch and mixing costs, we conducted two experiments. Experiment 1a was a near replication of Stephan and Koch in which conceptual overlap was present in the MC AV task. In contrast, Experiment 1b reduced conceptual overlap within the MC AV task and increased it in the MI VV task. In Experiment 1a, we replicated Stephan and Koch's findings: larger switch costs were observed for the MI pair; in Experiment 1b, we found numerically greater switch costs in the MC condition. In Experiment 2, we reduced conceptual overlap in both tasks and found no effect of modality compatibility on switch costs. However, mixing costs were primarily driven by modality compatibility, regardless of conceptual overlap. These results highlight the different roles that conceptual overlap and modality pairings have on switch and mixing costs.

Do small dual-task costs reflect ideomotor compatibility or the absence of crosstalk?

Dual-task costs can be greatly reduced or even eliminated when both tasks use highly-compatible S-R associations. According to Greenwald (Journal of Experimental Psychology: Human Perception and Performance, 30, 632-636, 2003), this occurs because the appropriate response can be accessed without engaging performance-limiting response selection processes, a proposal consistent with the embodied cognition framework in that it suggests that stimuli can automatically activate motor codes (e.g., Pezzulo et al., New Ideas in Psychology, 31(3), 270-290, 2013). To test this account, we reversed the stimulus-response mappings for one or both tasks so that some participants had to "do the opposite" of what they perceived. In these reversed conditions, stimuli resembled the environmental outcome of the alternative (incorrect) response. Nonetheless, reversed tasks were performed without costs even when paired with an unreversed task. This finding suggests that the separation of the central codes across tasks (e.g., Wickens, 1984) is more critical than the specific S-R relationships; dual-task costs can be avoided when the tasks engage distinct modality-based systems.

Searching working memory for the source of dual-task costs.

Dual-task costs depend on the specific pairings of stimulus and response modalities. Such findings are analogous to domain-specific effects in the working memory (WM) literature, in which items compete for limited capacity when they involve related types of information. The present study explicitly examines the relationship between modality-pairing effects on dual-task costs and domain-specificity effects on WM capacity. Participants maintained a sequence of either locations or tones in WM, and then performed a choice reaction time task in which they responded either vocally or manually. The stimuli for the choice reaction time task were held constant, but its response modality affected the interference observed in WM: vocal responses interfered with WM for tones and manual responses interfered with WM for locations. These findings indicate that response selection engages domain-specific WM processes and that interference within these processes may account for modality-pairing effects.