Using a Veto paradigm to investigate the decision models in explaining Libet-style experiments.

The question of whether free will exists or not has intrigued philosophers for centuries. About 40 years ago, cognitive neuroscientists such as Benjamin Libet have joined the discussion by demonstrating that an ERP component, the readiness potential (RP), precedes the reported time of decision to act by a few hundred milliseconds. Libet et al. (1983) argued that our brains unconsciously prepare the movement before we experience any conscious intention, which led some free will skeptics (e.g., Ebert & Wegner, 2011) to argue that free will does not exist. While Libet's interpretation of his findings initiated an intense philosophical debate, alternative interpretations have been put forward more recently (Bode et al., 2014; Brass et al., 2019; Schurger et al., 2012; 2021). Integration to bound models (ITB) of Libet-style experiments suggest that we accumulate information until an intention threshold is reached, which triggers our experience of intention and execution of voluntary behaviors. The RP, from this perspective reflects the decision process itself rather than the consequence of an unconscious decision. To determine if the ITB model better predicts behavioral patterns in Libet-style experiments, we added a whether-component to the classical Libet task (the Veto Libet task) and compared the behavioral measures in the Veto Libet task with the Classical Libet task. We hypothesized that the signal accumulation in the Veto Libet task would be less steep than in the Classical Libet task, resulting in longer wait times and earlier self-reported intentions to act (i.e., the W). The result in general supported our hypotheses. In addition, these behavioral differences between the Classical Libet task and the Veto Libet task established valuable behavioral correlates for future investigations into the vetoing phenomenon. Finally, this study was also the first application of the Libet task in an online setting, and the behavioral parameters were highly comparable to the previous offline studies, further supporting the possibility of using the online platform to study arbitrary decision-making.

Concurrent response and action effect representations across the somatomotor cortices during novel task preparation.

Instructions allow us to fulfill novel and complex tasks on the first try. This skill has been linked to preparatory brain signals that encode upcoming demands in advance, facilitating novel performance. To deepen insight into these processes, we explored whether instructions pre-activated task-relevant motoric and perceptual neural states. Critically, we addressed whether these representations anticipated activity patterns guiding overt sensorimotor processing, which could reflect that internally simulating novel tasks facilitates the preparation. To do so, we collected functional magnetic resonance imaging data while female and male participants encoded and implemented novel stimulus-response associations. Participants also completed localizer tasks designed to isolate the neural representations of the mappings-relevant motor responses, perceptual consequences, and stimulus categories. Using canonical template tracking, we identified whether and where these sensorimotor representations were pre-activated. We found that response-related templates were encoded in advance in regions linked with action control, entailing not only the instructed responses but also their somatosensory consequences. This result was particularly robust in primary motor and somatosensory cortices. While, following our predictions, we found a systematic decrease in the irrelevant stimulus templates' representational strength compared to the relevant ones, this difference was due to below-zero estimates linked to the irrelevant category activity patterns. Overall, our findings reflect that instruction processing relies on the sensorimotor cortices to anticipate motoric and kinesthetic representations of prospective action plans, suggesting the engagement of motor imagery during novel task preparation. More generally, they stress that the somatomotor system could participate with higher-level frontoparietal regions during anticipatory task control.

Anticipated imitation of multiple agents.

It is well-established that people tend to mimic one another's actions, a crucial aspect of social interactions. Anticipating imitation has been shown to boost motor activation and reaction times for congruent actions. However, prior research predominantly focused on dyads, leaving gaps in our knowledge regarding group dynamics. This study addresses this gap, conducting three experiments using extensive online data. Participants engaged in anticipated imitation tasks with one versus three virtual agents. The results across all three experiments (n = 77; n = 239; n = 457) consistently support the existence of an anticipated imitation effect, with faster reaction times for congruent actions. Furthermore, the research unveils a social facilitation effect, with participants reacting more swiftly when anticipating three agents compared to one. However, we did not find the expected increase of the congruency effect with multiple agents; rather, the data indicates that anticipating multiple agents instead decreases this effect. These findings are discussed within the framework of ideomotor theory, offering insights into how they relate to recent research on the automatic imitation of multiple agents.

Dynamic changes in task preparation in a multi-task environment: The task transformation paradigm.

A key element of human flexible behavior concerns the ability to continuously predict and prepare for sudden changes in tasks or actions. Here, we tested whether people can dynamically modulate task preparation processes and decision-making strategies when the identity of a to-be-performed task becomes uncertain. To this end, we developed a new paradigm where participants need to prepare for one of nine tasks on each trial. Crucially, in some blocks, the task being prepared could suddenly shift to a different task after a longer cue-target interval, by changing either the stimulus category or categorization rule that defined the initial task. We found that participants were able to dynamically modulate task preparation in the face of this task uncertainty. A second experiment shows that these changes in behavior were not simply a function of decreasing task expectancy, but rather of increasing switch expectancy. Finally, in the third and fourth experiment, we demonstrate that these dynamic modulations can be applied in a compositional manner, depending on whether either only the stimulus category or categorization rule would be expected to change.

Internal attention modulates the functional state of novel stimulus-response associations in working memory.

Information in working memory (WM) is crucial for guiding behavior. However, not all WM representations are equally relevant simultaneously. Current theoretical frameworks propose a functional dissociation between 'latent' and 'active' states, in which relevant representations are prioritized into an optimal (active) state to face current demands, while relevant information that is not immediately needed is maintained in a dormant (latent) state. In this context, task demands can induce rapid and flexible prioritization of information from latent to active state. Critically, these functional states have been primarily studied using simple visual memories, with attention selecting and prioritizing relevant representations to serve as templates to guide subsequent behavior. It remains unclear whether more complex WM representations, such as novel stimulus-response associations, can also be prioritized into different functional states depending on their task relevance, and if so how these different formats relate to each other. In the present study, we investigated whether novel WM-guided actions can be brought into different functional states depending on current task demands. Our results reveal that planned actions can be flexibly prioritized when needed and show how their functional state modulates their influence on ongoing behavior. Moreover, they suggest the representations of novel actions of different functional states are maintained in WM via a non-orthogonal coding scheme, thus are prone to interference.

Instructing somebody else to act: motor co-representations in the instructor.

Instructions enable humans to perform novel tasks quickly. This is achieved by creating and activating the instruction representation for upcoming tasks, which can then modulate ongoing task behaviour in an almost 'reflexive' manner, an effect called instruction-based reflexivity. While most research has focused on understanding how verbal instructions are represented within the 'instructed' (i.e. the person receiving instructions), here we focus on how the instructor's (i.e. the person giving instructions) behaviour is affected through instructing. In a series of three experiments and one pooled analysis, we extended the classical instruction-based reflexivity paradigm to a novel social variant in which the instructions are given by an instructor (rather than visual computer-generated instructions). We found an instruction-based reflexivity effect for the instructor, that is, the instructor's task performance was better on congruent compared to incongruent trials (i.e. Experiments 1 and 2, pooled analysis). This suggests that the instructor represents the instructions of the instructed in an action-oriented format. However, this did not depend on the specific task of the instructed (i.e. Experiment 1), nor is it exclusively social (i.e. Experiment 3).

Associative Visuomotor Learning Using Transcranial Magnetic Stimulation Induces Stimulus-Response Interference.

Classical conditioning states that the systematic co-occurrence of a neutral stimulus with an unconditioned stimulus can cause the neutral stimulus to, over time, evoke the same response as the unconditioned stimulus. On a neural level, Hebbian learning suggests that this type of learning occurs through changes in synaptic plasticity when two neurons are simultaneously active, resulting in increased connectivity between them. Inspired by associative learning theories, we here investigated whether the mere co-activation of visual stimuli and stimulation of the primary motor cortex using TMS would result in stimulus-response associations that can impact future behavior. During a learning phase, we repeatedly paired the presentation of a specific color (but not other colors) with a TMS pulse over the motor cortex. Next, participants performed a two-alternative forced-choice task where they had to categorize simple shapes and we studied whether the shapes' task-irrelevant color (and its potentially associated involuntary motor activity) affected the required motor response. Participants showed more errors on incongruent trials for stimuli that were previously paired with high intensity TMS pulses, but only when tested on the same day. Using a drift diffusion model for conflict tasks, we further demonstrate that this interference occurred early, and gradually increased as a function of associated TMS intensity. Taken together, our findings show that the human brain can learn stimulus-response associations using externally induced motor cortex stimulation. Although we were inspired by the Hebbian learning literature, future studies should investigate whether Hebbian or other learning processes were also what brought about this effect.

Covert and overt automatic imitation are correlated.

Most theoretical accounts of imitation assume that covert and overt measures of automatic imitation tap into the same underlying construct. Despite this widespread assumption, it is not well supported by empirical evidence. In fact, the only study investigating the relation between covert and overt automatic imitation failed to find a correlation between them (Genschow et al., 2017, PLOS ONE, 12[9], Article e0183784). However, because overt and covert imitation were measured using two very different tasks, and because the measure of overt imitation was found to be unreliable, it is still not clear whether a correlation between both measures exists. Here, we address this question by reanalyzing the results of a previous virtual reality study in which automatic imitation was indexed with an overt and covert measure of gaze following, both obtained within one and the same task (Cracco et al., 2022, IScience, Article 104891). The results show that, in this situation, both types of imitation do correlate. As such, our results provide support for the idea that overt and covert measures of automatic imitation measure the same underlying construct.

Effects of Experiencing CS-US Pairings on Instructed Fear Reversal.

Fear learning allows us to identify and anticipate aversive events and adapt our behavior accordingly. This is often thought to rely on associative learning mechanisms where an initially neutral conditioned stimulus (CS) is repeatedly paired with an aversive unconditioned stimulus (US), eventually leading to the CS also being perceived as aversive and threatening. Importantly, however, humans also show verbal fear learning. Namely, they have the ability to change their responses to stimuli rapidly through verbal instructions about CS-US pairings. Past research on the link between experience-based and verbal fear learning indicated that verbal instructions about a reversal of CS-US pairings can fully override the effects of previously experienced CS-US pairings, as measured through fear ratings, skin conductance, and fear-potentiated startle. However, it remains an open question whether such instructions can also annul learned CS representations in the brain. Here, we used a fear reversal paradigm (female and male participants) in conjunction with representational similarity analysis of fMRI data to test whether verbal instructions fully override the effects of experienced CS-US pairings in fear-related brain regions or not. Previous research suggests that only the right amygdala should show lingering representations of previously experienced threat ("pavlovian trace"). Unexpectedly, we found evidence for the residual effect of prior CS-US experience to be much more widespread than anticipated, in the amygdala but also cortical regions like the dorsal anterior cingulate or dorsolateral prefrontal cortex. This finding shines a new light on the interaction of different fear learning mechanisms, at times with unexpected consequences.SIGNIFICANCE STATEMENT Humans are able to learn about aversive stimuli both from experience (i.e., repeated pairings of conditioned stimulus (CS) and unconditioned stimulus (US; pavlovian conditioning), and from verbal instructions about stimulus pairings. Understanding how experience-based and verbal learning processes interact is key for understanding the cognitive and neural underpinnings of fear learning. We tested whether prior aversive experiences (CS-US pairings) affected subsequent verbal learning, searching for lingering threat signals after verbal instructions reversed a CS from being threatening to being safe. While past research suggested such threat signals can only be found in the amygdala, we found evidence to be much more widespread, including the medial and lateral PFC. This highlights how experience-based and verbal learning processes interact to support adaptive behavior.

Adaptive coding of stimulus information in human frontoparietal cortex during visual classification.

The neural mechanisms of how frontal and parietal brain regions support flexible adaptation of behavior remain poorly understood. Here, we used functional magnetic resonance imaging (fMRI) and representational similarity analysis (RSA) to investigate frontoparietal representations of stimulus information during visual classification under varying task demands. Based on prior research, we predicted that increasing perceptual task difficulty should lead to adaptive changes in stimulus coding: task-relevant category information should be stronger, while task-irrelevant exemplar-level stimulus information should become weaker, reflecting a focus on the behaviorally relevant category information. Counter to our expectations, however, we found no evidence for adaptive changes in category coding. We did find weakened coding at the exemplar-level within categories however, demonstrating that task-irrelevant information is de-emphasized in frontoparietal cortex. These findings reveal adaptive coding of stimulus information at the exemplar-level, highlighting how frontoparietal regions might support behavior even under challenging conditions.

EEG frequency tagging evidence of intact social interaction recognition in adults with autism.

To explain the social difficulties in autism, many studies have been conducted on social stimuli processing. However, this research has mostly used basic social stimuli (e.g., eyes, faces, hands, single agent), not resembling the complexity of what we encounter in our daily social lives and what people with autism experience difficulties with. Third-party social interactions are complex stimuli that we come across often and are also highly relevant for social functioning. Interestingly, the existing behavioral studies point to altered social interaction processing in autism. However, it is not clear whether this is due to altered recognition or altered interpretation of social interactions. Here, we specifically investigated the recognition of social interaction in adults with and without autism. More precisely, we measured neural responses to social scenes depicting either social interaction or not with an electroencephalogram frequency tagging task and compared these responses between adults with and without autism (N = 61). The results revealed an enhanced response to social scenes with interaction, replicating previous findings in a neurotypical sample. Crucially, this effect was found in both groups, with no difference between them. This suggests that social interaction recognition is not atypical in adults with autism. Taken together with the previous behavioral evidence, our study thus suggests that individuals with autism are able to recognize social interactions, but that they might not extract the same information from those interactions or that they might use the extracted information differently.

Manipulating free will beliefs using online video games.

Research in social psychology and experimental philosophy has investigated lay people's free will beliefs (FWB). Using different approaches (i.e. experimental manipulations and vignette studies), they investigated how FWB relate to other concepts, and whether changing FWB has an impact on downstream processes such as social behavior. However, both approaches have shortcomings. While experimental manipulations used in social psychology suffer from demand effects, vignettes used in experimental philosophy are often highly abstract. Across two pre-registered studies, we developed a new approach by merging them in an online video game setting. Using this novel, experience-based FWB manipulation, we found that decreasing FWB impacted variables such as perceived control and responsibility in both studies. While the experience-based manipulation influenced participants' beliefs in free will within the context of the experience ("Within the context of the scenario, would the agent believe in free will?") in the first study, this manipulation effect did not transfer to participants' general FWB ("Do you believe in free will?") in the second study. Overall, our findings suggest a way forward in studying laypeople's beliefs in free will.

The relevance of familiarity in the context of self-related information processing.

Humans are inclined to preferentially process self-related content, referred to as the "self-bias." Different paradigms have been used to study this effect. However, not all paradigms included a familiar other condition (but rather an unfamiliar other condition), needed to differentiate self-specific effects from the impact of familiarity. The primary goal of our study was to test the suitability for studying the self-bias of two paradigms that provide robust measures of salience effects-that is, the Repetition Blindness (RB) effect and the Emotional Stroop (ES) interference-while addressing the familiarity confound. We further explored whether self-bias effects were related to autism symptomatology, as a reduced self-bias in autism has been reported in previous research. In an online procedure, 82 adults performed an RB task and an ES task in a counterbalanced order, while being presented with both self- and familiar other-related stimuli. Results of both frequentist and Bayesian analyses did not provide evidence in favour of a specific self-bias on either task: we found no significant modulation of the RB effect, nor of the ES interference, for the own versus a close other's name. Moreover, no link with autism symptomatology was found. Tackling a crucial shortcoming from earlier studies, our investigation raises awareness on the importance of accounting for familiarity when investigating self-related processing.

Manipulating Belief in Free Will and Its Downstream Consequences: A Meta-Analysis.

Ever since some scientists and popular media put forward the idea that free will is an illusion, the question has risen what would happen if people stopped believing in free will. Psychological research has investigated this question by testing the consequences of experimentally weakening people's free will beliefs. The results of these investigations have been mixed, with successful experiments and unsuccessful replications. This raises two fundamental questions: Can free will beliefs be manipulated, and do such manipulations have downstream consequences? In a meta-analysis including 145 experiments (95 unpublished), we show that exposing individuals to anti-free will manipulations decreases belief in free will and increases belief in determinism. However, we could not find evidence for downstream consequences. Our findings have important theoretical implications for research on free will beliefs and contribute to the discussion of whether reducing people's belief in free will has societal consequences.

Does belief in free will influence biological motion perception?

Previous research suggests that belief in free will correlates with intentionality attribution. However, whether belief in free will is also related to more basic social processes is unknown. Based on evidence that biological motion contains intentionality cues that observers spontaneously extract, we investigate whether people who believe more in free will, or in related constructs, such as dualism and determinism, would be better at picking up such cues and therefore at detecting biological agents hidden in noise, or would be more inclined to detect intentionality cues and therefore to detect biological agents even when there are none. Signal detection theory was used to measure participants' ability to detect biological motion from scrambled background noise (d') and their response bias (c) in doing so. In two experiments, we found that belief in determinism and belief in dualism, but not belief in free will, were associated with biological motion perception. However, no causal effect was found when experimentally manipulating free will-related beliefs. In sum, our results show that biological motion perception, a low-level social process, is related to high-level beliefs about dualism and determinism.

The impact of free will beliefs on implicit learning.

A growing number of studies demonstrate that belief in free will (FWB) is dynamic, and can be reduced experimentally. Most of these studies assume that doing so has beneficial effects on behavior, as FWBs are thought to subdue unwanted automatic processes (e.g. racial stereotypes). However, relying on automatic processes can sometimes be advantageous, for instance during implicit learning (e.g. detecting and exploiting statistical regularities in the environment). In this registered report, we tested whether experimentally reducing FWBs positively affected implicit motor learning. We hypothesized that reducing FWBs would lead to both faster and stronger implicit learning, as measured using the alternating serial reaction time (ASRT) task. While we did show a manipulation effect on free will beliefs, there was no detectable effect on implicit learning processes. This finding adds to the growing body of evidence that free will belief manipulations do not meaningfully affect downstream behavior.

Top-Down Modulation of Motor Priming by Belief About Animacy.

Research has shown that people automatically imitate others and that this tendency is stronger when the other person is a human compared with a nonhuman agent. However, a controversial question is whether automatic imitation is also modulated by whether people believe the other person is a human. Although early research supported this hypothesis, not all studies reached the same conclusion and a recent meta-analysis found that there is currently neither evidence in favor nor against an influence of animacy beliefs on automatic imitation. One of the most prominent studies supporting such an influence is the study by Liepelt and Brass (2010), who found that automatic imitation was stronger when participants believed an ambiguous, gloved hand to be human, as opposed to wooden. In this registered report, we provide a high-powered replication of this study (N = 199). In contrast to Liepelt and Brass (2010), we did not find an effect of animacy beliefs on automatic imitation. However, we did find a correlation between automatic imitation and perceived self-other similarity. Together, these results suggest that the gloved hand procedure does not reliably influence automatic imitation, but interindividual differences in perceived similarity do.

Evidence for a two-step model of social group influence.

Social group influence plays an important role in societally relevant phenomena such as rioting and mass panic. One way through which groups influence individuals is by directing their gaze. Evidence that gaze following increases with group size has typically been explained in terms of strategic processes. Here, we tested the role of reflexive processes. In an ecologically valid virtual reality task, we found that participants were more likely to follow the group's gaze when more people looked, even though they knew the group provided no relevant information. Interestingly, participants also sometimes changed their mind after starting to follow the gaze of the group, indicating that automatic imitation can be overruled by strategic processes. This suggests that social group influence is best explained by a two-step model in which bottom-up imitative processes first elicit a reflexive tendency to imitate, before top-down strategic processes determine whether to execute or inhibit this reflex.

Concurrently observed actions are represented not as compound actions but as independent actions.

Recent research suggests that we can simultaneously represent the actions of multiple agents in our motor system. However, it is unclear exactly how concurrently observed actions are represented. Here, we tested two competing hypotheses. According to the independence hypothesis, concurrently observed actions are represented as independent actions. According to the compound hypothesis, they are instead integrated, whenever possible, into compound actions. In Experiment 1 (N = 32), we first show that the standard imitation-inhibition task with a single hand can be extended to measure automatic imitation of compound actions. In Experiments 2-5 (NTotal = 368), we then investigated the representation of concurrently observed actions by further extending this task to include two hands. The results showed that two hands performing two different actions (e.g., one hand lifts index finger, one hand lifts middle finger) produced an effect similar to that of both hands performing just one of those actions (e.g., both hands lift index finger) but different from that of both hands performing both actions together (i.e., a compound action; lift both index and middle finger). This indicates that concurrently observed actions are coded as independent actions in the motor system. (PsycInfo Database Record (c) 2022 APA, all rights reserved).