Valentin Koob

Objective: We examined how response–effect (RE), stimulus–response (SR), and stimulus–effect (SE) compatibility jointly influence performance in lever tool use, and test the robustness of previous results across different input modalities. Background: According to the ideomotor principle, motor actions are selected via anticipating their effects. This becomes particularly relevant in tool use, where the relationship between hand movement and tool movement might be inverted. While various compatibilities are known to influence performance, their interactions remain poorly understood. Method: We built upon work by Müsseler and Skottke (2011) using orthogonal manipulations of RE, SR, and SE compatibility. Across four experiments with student samples (2022–2024), we varied input modality (button presses, continuous sliders, touchless gestures) and lever rotation type (discrete vs. continuous) to assess the generalizability of the original findings. Results: Müsseler and Skottke (2011) showed that the interaction of SR and SE compatibility depends on the RE compatibility condition. Consistent with this, we found that under RE compatible conditions, performance was improved when SR and SE compatibilities aligned. However, under RE incompatible conditions, the SR × SE interaction disappeared with button press responses (Experiments 1 and 2) or reversed with more continuous responses (Experiments 3 and 4). Conclusion: These findings highlight the dynamic interplay of various compatibility relations for untrained participants, and that this interplay depends on, for example, the input device. Application: Our results inform the design of human-tool interfaces by highlighting when aligning response–effect mappings benefits performance and when mismatches can alter or even reverse other compatibility relationships.

A central question in cognitive psychology concerns how humans selectively attend to task-relevant information while ignoring task-irrelevant information. This question is frequently studied using conflict tasks, such as the Simon, Eriksen flanker, and Stroop tasks that require responses to relevant stimulus features while ignoring irrelevant and potentially conflicting features. All conflict tasks produce better performance in congruent trials where task-relevant features and irrelevant features match compared with when they mismatch in incongruent trials: the congruency effect. However, they differ markedly in the temporal dynamics of this congruency effect and accordingly in their RT distributions. The Diffusion Model for Conflict tasks (DMC) was introduced as a model to formally account for all distributional patterns in conflict tasks. It integrates dual-route theories of cognitive control into the framework of sequential sampling models by positing two superimposed, independent evidence accumulation processes: a linear one for controlled processing of the task-relevant information, and a pulse-like one for automatic processing of the task-irrelevant information, in which activation first increases until a maximum and then decreases again. This review summarizes DMC’s architecture, its core parameters, and its ability to account for various distributional patterns. We review and discuss applications of DMC across several psychological domains, and technical considerations such as parameter estimation and recovery. Limitations of the model are critically assessed, and fields of open research are outlined. Overall, DMC offers a general account of conflict processing. While a powerful tool for quantifying the dynamics of selective attention and cognitive control, there is still a limited standardization in its application, and more research is needed to extend DMC to other classes of conflict tasks.

In dual-task experiments, overlapping response characteristics of two successive tasks affect performance not only in Task 2 but also in Task 1. This observation is termed the backward crosstalk effect and is often explained by activated Task 2 response information influencing Task 1 response selection. In the present study, we describe and evaluate three diffusion models that specify Task 2 response activation as either linear, asymptotic, or pulse-like. Formal model comparisons and a parameter recovery suggest that linear Task 2 response activation is most accurate for most individuals. However, we also highlight the potential role of individual differences, as a pulse-like Task 2 response activation function may better describe a subset of individuals. Finally, we provide practical recommendations for researchers on how to fit the backward crosstalk effect in the larger context of dual-tasking. (PsycInfo Database Record (c) 2025 APA, all rights reserved).

A central question in cognitive psychology concerns how humans selectively attend totask-relevant information whilst ignoring task-irrelevant information. This question isfrequently studied using conflict tasks, such as the Simon, Eriksen flanker, and Strooptasks, that require responses to relevant stimulus features while ignoring irrelevant, andpotentially conflicting, features. While all conflict tasks produce better performance ontrials where task-relevant features and irrelevant features match—a phenomenon known asthe congruency effect—they differ markedly in their RT distributions. The Diffusion Modelfor Conflict tasks (DMC) was introduced as a model to formally account for alldistributional patterns in conflict tasks. It integrates dual-route theories of cognitivecontrol into the framework of sequential sampling models by positing two superimposed,independent evidence accumulation processes: a linear one for controlled processing of thetask-relevant information, and a pulse-like one for automatic processing of thetask-irrelevant information, where activation first increases until a maximum and thendecreases again. This review summarizes DMC’s architecture, its core parameters, and itsability to account for various distributional patterns. We review and discuss applications ofDMC across several psychological domains, and technical considerations such as parameterestimation and recovery. Limitations of the model are critically assessed, and fields of openresearch are outlined. Overall, DMC offers a general account of conflict processing. Whilea powerful tool for quantifying the dynamics of selective attention and cognitive control,there is still a limited standardization in its application and more research is needed toextend DMC to other classes of conflict tasks.

In conflict tasks, such as the Simon, Eriksen flanker, or Stroop task, a relevant and an irrelevant feature indicate the same or different responses in congruent and incongruent trials, respectively. The congruency effect refers to faster and less error-prone responses in congruent relative to incongruent trials. Distributional analyses reveal that the congruency effect in the Simon task becomes smaller with increasing RTs, reflected by a negative-going delta function. In contrast, for other tasks, the delta function is typically positive-going, meaning that congruency effects become larger with increasing RTs. The Diffusion Model for Conflict tasks (DMC; Ulrich et al., Cognitive Psychology, 78, 148–174, 2015) accounts for this by explicitly modeling the information accumulated from the relevant and the irrelevant features and attributes negatively- versus positively-sloped delta functions to different peak times of a pulse-like activation resulting from the task-irrelevant feature. Because the underlying function implies negative drift rates, Lee and Sewell (Psychonomic Bulletin & Review, 31(5), 1–31, 2024) recently questioned this assumption and suggested their Revised Diffusion Model for Conflict tasks (RDMC). We address three issues regarding RDMC compared to DMC: (1) The pulse-like function is not as implausible as Lee and Sewell suggest. (2) RDMC itself comes with a questionable assumption that different parameters are required for congruent and incongruent trials. (3) Moreover, we present data from a new parameter recovery study, suggesting that RDMC lacks acceptable recovery of several parameters (in particular compared to DMC). In this light, we discuss RDMC as not (yet) a revised version of DMC.

Using mathematical models of human cognition has become an increasingly important and valuable research tool in many different fields of psychological research and neighboring areas. Widely used are drift diffusion models (DDMs) that can be used to predict probability density functions (PDFs) of binary choice reaction tasks. Often, the parameters of such a model are time-independent (i.e., they do not vary as a function of time within a trial). However, the more general case is that of time-dependent parameters. Several recent models, for example, assume time-dependency for the drift rate and/or the boundaries. Such time-dependent (or non-stationary) models increase mathematical complexity, but several solutions to approximate the PDFs have been advanced. We here present dRiftDM, an R package particularly designed to meet the needs of psychological research. This package approximates the PDFs by solving the Kolmogorov-Forward-Equation to handle time-dependent models as well. Fitting a model to data can be done participant-wise, and model parameters and statistics are easily accessible and can be visualized directly to provide information about (qualitative) model fits. Hands-on examples for using pre-built models and for developing own models are provided.

When simultaneously performing two tasks that share response properties, interference can occur. Besides general performance decrements, performance in the first task is worse when the second task requires a spatially incompatible response, known as the backward crosstalk effect (BCE). The size of this BCE, similar to congruency effects in conflict tasks, is subject to a sequential modulation, with a smaller BCE after incompatible compared to compatible trials. In the present study, we focus on a potential bidirectional interaction between crosstalk (and its resolution) at a lower level of task performance and higher-order processes of task organization. Two questions were of particular interest: First, do participants switch task order more frequently after a conflict-prone incompatible trial than after a compatible trial? Second, does changing task order influence the efficiency of conflict resolution, as indexed by the size of the sequential modulation of the BCE. Across four experiments, we only found marginal evidence for an influence of lower-level conflict on higher-order processes of task organization, with only one experiment revealing a tendency to repeat task order following conflict. Our results thus suggest practical independence between conflict and task-order control. When separating processes of task selection and task performance, the sequential modulation was generally diminished, suggesting that conflict resolution in dual-tasks can be disrupted by a deliberate decision about task order, or, alternatively, by a longer inter-trial interval. Finally, the study found a strong bias towards repeating the same task order across trials, suggesting that task-order sets not only impact task performance but also guide task selection.

When two speeded tasks have spatially overlapping responses, preactivated Task 2 (T2) response information influences Task 1 (T1) response selection, a phenomenon known as the backward crosstalk effect (BCE). Current models of the BCE implicitly assume that T2 response information is equally present in trials requiring compatible or incompatible responses, such that T1 performance improves when T2 requires a compatible response and deteriorates when T2 requires an incompatible response. Thus, T2 response information should have a facilitatory and an interfering effect on T1. Interestingly, this hypothesis has never been tested, and the present study (conducted between 2021 and 2023) attempts to fill this gap by using neutral trials in which T2 responses did not spatially overlap with those in T1. The results suggest that the BCE (in T1) reflects both facilitation and interference effects of comparable magnitude, thus corroborating current conceptualizations of the BCE. We also observed an unexpected pattern of effects for T2, with only an interference effect, but no facilitation effect. Additional experiments led us to conclude that the T2 result was sensitive to the specific task characteristics. Conclusions about how the crosstalk transfers from T1 to T2 when switching tasks are therefore not possible. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

In dual-task experiments, overlapping response characteristics of two subsequently performed tasks may not only affect performance in Task 2 but also in Task 1. This phenomenon is often explained through activated Task 2 response information influencing Task 1 response selection, which then possibly propagates again into Task 2. So far, however, only little is known about (a) the time course of this Task 2 response activation and (b) possible transmission/propagation mechanisms. The present study addressed both issues by testing 10 plausible drift-diffusion models with 5 data sets from dual-task experiments. To this end, we first examined if the temporal course of the response activation is linearly increasing or pulse like. The pulse-like model turned out to be superior, but the corresponding dynamics of the response activation often described a monotonically increasing function that reached its peak late during Task 1 processing. By extending the pulse-like model with an additional diffusion process, we then examined whether and how the Task 2 response information could affect subsequent Task 2 response selection. Concerning the transmission mechanisms, none of the assumed models proved to be entirely satisfactory. However, additional simulations suggest that Task 2 response activation-transmission does not occur at all. Instead, a model in which Task 2 started with a trace of the previous Task 1 response (i.e., irrespective of the preexisting Task 2 activation) turned out to be the most promising account. (PsycInfo Database Record (c) 2023 APA, all rights reserved).