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In dual-task situations, mutual interference phenomena are often observed. One particularly interesting example of such phenomena is that even Task 1 performance is improved if Task 2 requires a compatible (e.g., both responses are given on the left side) instead of an incompatible response (e.g., one response is given on the right side, and the other on the left side). This is called the compatibility-based backward crosstalk effect (BCE). In a previous paper, we observed support for a critical role of stimulus-response (S-R) links in causing this effect: The BCE was smaller when one of the two tasks was a free choice task. However, an alternative explanation for this observation is that free choice tasks lead to immediate conflict adaptation, thereby reducing the interference from the other task. In the present two experiments, we tested this explanation by varying the amount of conflict assumed to be induced by a free choice task either sequentially (Exp. 1) or block-wise (Exp. 2). While we replicated a sequential modulation of the BCE with two forced choice tasks, we observed (1) no reduction of the BCE induced by (compatible) free choice trials nor (2) an effect of block-wise manipulations of the frequency of free choice trials on the size of the BCE. Thus, while the BCE is sensitive to sequential modulations induced by the (in)compatibility of two forced choice responses, which might point to conflict adaptation, the reduced BCE in dual-task situations involving a free choice task is likely due to its weaker S-R links.

Response times (RTs) for free choice tasks are usually longer than those for forced choice tasks. We examined the cause for this difference in a study with intermixed free and forced choice trials, and adopted the rationale of sequential sampling frameworks to test two alternative accounts: Longer RTs in free choices are caused (1) by lower rates of information accumulation, or (2) by additional cognitive processes that delay the start of information accumulation. In three experiments, we made these accounts empirically discriminable by manipulating decision thresholds via the frequency of catch trials (Exp. 1) or via inducing time pressure (Exp. 2 and 3). Our results supported the second account, suggesting a temporal delay of information accumulation in free choice tasks, while the accumulation rate remains comparable. We propose that response choice in both tasks relies on information accumulation towards a specific goal. While in forced choice tasks, this goal is externally determined by the stimulus, in free choice tasks, it needs to be generated internally, which requires additional time.

Everyday life offers a variety of possible actions, from which we choose one that corresponds to our intended goals. How do these goals and actions interact within the mind? One way to investigate this question is free-choice tasks, where participants freely choose the action they want to perform on any given trial. Such tasks are used in research on voluntary actions and goal-driven behavior, such as ideomotor theory. However, these tasks leave participants with a substantial amount of freedom and allow for different response strategies. Such strategies can, though being hidden in the final data, influence the results, for example by hiding the effects of manipulations of interest. To better understand participants' behavior in free-choice tasks, we used mouse tracking in an ideomotor free-choice experiment, where participants learn the connection between an action and an effect. Subsequently, they have to freely choose between actions, while the former effect is presented as a stimulus. We identified two distinct groups that applied different decision strategies. The first group made the decision at the beginning of or before the trial, irrespective of the yet to be presented effect stimulus. The second group decided within the trial and was affected by the stimulus more often. This suggests that people handle free-choice tasks differently which is expressed in heterogeneous choice patterns and response times and an underestimation of the examined effects. These differences potentially limit the reliability of inferences from free-choice experiments and should be considered in the interpretation of their results., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Free choice tasks are tasks in which two or more equally valid response options per stimulus exist from which participants can choose. In investigations of the putative difference between self-generated and externally triggered actions, they are often contrasted with forced choice tasks, in which only one response option is considered correct. Usually, responses in free choice tasks are slower when compared with forced choice task responses, which may point to a qualitative difference in response selection. It was, however, also suggested that free choice tasks are in fact random generation tasks. Here, we tested the prediction that in this case, randomness of the free choice responses depends on working memory (WM) load. In Experiment 1, participants were provided with varying levels of external WM support in the form of displayed previous choices. In Experiment 2, WM load was induced via a concurrent n-back task. The data generally confirm the prediction: in Experiment 1, WM support improved both randomness and speed of responses. In Experiment 2, randomness decreased and responses slowed down with increasing WM load. These results suggest that free choice tasks have much in common with random generation tasks.

Doing two things at once is hard, and it is probably hard for various reasons. Here we aim to demonstrate that one so far barely considered reason is the monitoring of sensory action feedback, which detracts from processing of other concurrent tasks. To demonstrate this, we engaged participants in a psychological refractory period paradigm. The responses in the two tasks produced visual action effects. These effects occurred either immediately or they were delayed for the first of the two responses. We assumed that delaying these effects would engage a process of monitoring visual feedback longer, and delay a concurrent task more, as compared to immediate effects. This prediction was confirmed in two experiments. We discuss the reasons for feedback monitoring and its possible contribution to dual tasking.

In dual-tasks, characteristics of Task 2 responses can already affect performance in the preceding Task 1. This is called the backward crosstalk effect (BCE). To account for the BCE, it has been suggested that the appearance of the Task 2 stimulus automatically projects activation onto the corresponding response through (transient or direct) stimulus-response (S-R) links. One way to investigate this claim is to compare the size of the BCE for tasks where S-R links are differently strong. To this end, we here compared BCEs for forced- vs. free-choice tasks, with the S-R links assumed to be stronger in the former than in the latter task. In Experiments 1 and 2, Task 1 was either forced-choice or free-choice and Task 2 always forced-choice, and in Experiment 3 this order was reversed. A BCE was observed in all experiments with the forced-choice tasks, but in response times it was smaller in Experiments 1 and 2 and absent in Experiment 3 with the free-choice task. However, in free-choice Task 1 responses, a bias towards selecting the response required in Task 2 was observed. These results suggest that the strength of S-R links plays a role in determining the size of the BCE. Relations to other studies and alternative explanations are discussed., (Copyright © 2017. Published by Elsevier B.V.)

Humans appear to act in response to environmental demands or to pursue self-chosen goals. In the laboratory, these situations are often investigated with forced- and free-choice tasks: in forced-choice tasks, a stimulus determines the one correct response, while in free-choice tasks the participants choose between response alternatives. We compared these two tasks regarding their susceptibility to dual-task interference when the concurrent task was always forced-choice. If, as was suggested in the literature, both tasks require different "action control systems," larger dual-task costs for free-choice tasks than for forced-choice tasks should emerge in our experiments, due to a time-costly switch between the systems. In addition, forced-choice tasks have been conceived as "prepared reflexes" for which all intentional processing is said to take place already prior to stimulus onset giving rise to automatic response initiation upon stimulus onset. We report three experiments with different implementations of the forced- vs. free-choice manipulation. In all experiments we replicated slower responses in the free- than in the forced-choice task and the typical dual-task costs. These latter costs, however, were equivalent for forced- and free-choice tasks. These results are easier to reconcile with the assumption of one unitary "action control system."

Choosing among different options is costly. Typically, response times are slower if participants can choose between several alternatives (free-choice) compared to when a stimulus determines a single correct response (forced-choice). This performance difference is commonly attributed to additional cognitive processing in free-choice tasks, which require time-consuming decisions between response options. Alternatively, the forced-choice advantage might result from facilitated perceptual processing, a prediction derived from the framework of implementation intentions. This hypothesis was tested in three experiments. Experiments 1 and 2 were PRP experiments and showed the expected underadditive interaction of the SOA manipulation and task type, pointing to a pre-central perceptual origin of the performance difference. Using the additive-factors logic, Experiment 3 further supported this view. We discuss the findings in the light of alternative accounts and offer potential mechanisms underlying performance differences in forced- and free-choice tasks.

Which motor actions are preferred to replace an initially planned but momentary not executable action? Previous research (Khan, Mourton, Buckolz, Adams, & Hayes, 2010, Acta Psychologica) suggests that anatomical constraints seem to be a major determinant for such choices: For example, participants more frequently chose to respond with the finger homologous to the prepared one. We argue that in this case finger homology is confounded with action effect similarity, and action effects have been ascribed a crucial role in action selection. We report two experiments. Experiment 1 replicated the results obtained by Khan et al. In Experiment 2, we introduced visual action effects in the paradigm. Results from this experiment clearly point to a role of effect similarity in addition to mere finger homology status for the choice frequency effect., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Humans make numerous choices every day and tend to perceive these choices as free. The present study shows how simple free choices are biased by experiencing unrelated auditory information. In two experiments, participants categorized tones according to their intensity on the dimensions volume and duration on the majority of trials. On some trials, however, they were to randomly generate a number, and we found these choices to be influenced by tone intensity. Particularly, if participants were cued toward volume, loud tones clearly biased participants to generate larger numbers. For tone duration, a similar effect only emerged if spatial information was reinforced by the motor context of the task. The findings extend previous findings relating to the ATOM framework (A Theory of Magnitude) by an explicit focus on auditory magnitude processing. As such, they also constrain ATOM by showing that the connections between different magnitude dimensions vary to a considerable degree., (Copyright © 2013 Elsevier Inc. All rights reserved.)