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.

Evidence for a role of synchrony but not common fate in the perception of biological group movements.

Extensive research has shown that observers are able to efficiently extract summary information from groups of people. However, little is known about the cues that determine whether multiple people are represented as a social group or as independent individuals. Initial research on this topic has primarily focused on the role of static cues. Here, we instead investigate the role of dynamic cues. In two experiments with male and female human participants, we use EEG frequency tagging to investigate the influence of two fundamental Gestalt principles - synchrony and common fate - on the grouping of biological movements. In Experiment 1, we find that brain responses coupled to four point-light figures walking together are enhanced when they move in sync vs. out of sync, but only when they are presented upright. In contrast, we found no effect of movement direction (i.e., common fate). In Experiment 2, we rule out that synchrony takes precedence over common fate by replicating the null effect of movement direction while keeping synchrony constant. These results suggest that synchrony plays an important role in the processing of biological group movements. In contrast, the role of common fate is less clear and will require further research.

EEG Frequency Tagging Reveals the Integration of Form and Motion Cues into the Perception of Group Movement.

The human brain has dedicated mechanisms for processing other people's movements. Previous research has revealed how these mechanisms contribute to perceiving the movements of individuals but has left open how we perceive groups of people moving together. Across three experiments, we test whether movement perception depends on the spatiotemporal relationships among the movements of multiple agents. In Experiment 1, we combine EEG frequency tagging with apparent human motion and show that posture and movement perception can be dissociated at harmonically related frequencies of stimulus presentation. We then show that movement but not posture processing is enhanced when observing multiple agents move in synchrony. Movement processing was strongest for fluently moving synchronous groups (Experiment 2) and was perturbed by inversion (Experiment 3). Our findings suggest that processing group movement relies on binding body postures into movements and individual movements into groups. Enhanced perceptual processing of movement synchrony may form the basis for higher order social phenomena such as group alignment and its social consequences.

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.

Model expertise does not influence automatic imitation.

Social learning theories state that new skills can be learned by observing others. Automatic imitation is thought to play an important role in this process. However, whether imitation is beneficial to learning critically depends on the expertise of the imitated person. Therefore, the aim of this study was to investigate the influence of model expertise on automatic imitation, by comparing automatic imitation of an expert and non-expert model in two within-subject experiments. In a first experiment (N = 61), we manipulated the perception of expertise in one task and tested how this influenced automatic imitation in a separate task. However, in contrast to our hypothesis, and in spite of a successful manipulation check, we did not find evidence for an effect of model expertise on imitative behavior. To exclude the alternative explanation that this was due to a lack of transfer of expertise attribution, we then conducted a second, preregistered experiment (N = 125), in which we manipulated model expertise using the same task also used to measure automatic imitation. However, in line with the results of Experiment 1, we found no evidence for an effect of model expertise on imitative behavior. These results put important constraints on the role of automatic imitation in motor learning.

Group membership does not modulate automatic imitation.

Individuals have the automatic tendency to imitate each other. A key prediction of different theories explaining automatic imitation is that individuals imitate in-group members more strongly than out-group members. However, the empirical basis for this prediction is rather inconclusive. Only a few experiments have investigated the influence of group membership using classic automatic imitation paradigms and these experiments led to mixed results. To put the group membership prediction to a critical test, we carried out six high-powered experiments (total N = 1538) in which we assessed imitation with the imitation-inhibition task and manipulated group membership in different ways. Evidence across all experiments indicates that group membership does not modulate automatic imitation. Moreover, we do not find support for the idea that feelings of affiliation or perceived similarity moderate the effect of group membership on automatic imitation. These results have important implications for theories explaining automatic imitation and contribute to the current discussion of whether automatic imitation can be socially modulated.

Representing Multiple Observed Actions in the Motor System.

There is now converging evidence that others' actions are represented in the motor system. However, social cognition requires us to represent not only the actions but also the interactions of others. To do so, it is imperative that the motor system can represent multiple observed actions. The current fMRI study investigated whether this is possible by measuring brain activity from 29 participants while they observed 2 right hands performing sign language gestures. Three key results were obtained. First, brain activity in the premotor and parietal motor cortex was stronger when 2 hands performed 2 different gestures than when 1 hand performed a single gesture. Second, both individual observed gestures could be decoded from brain activity in the same 2 regions. Third, observing 2 different gestures compared with 2 identical gestures activated brain areas related to motor conflict, and this activity was correlated with parietal motor activity. Together, these results show that the motor system is able to represent multiple observed actions, and as such reveal a potential mechanism by which third-party social encounters could be processed in the brain.

Defining the neural correlates of spontaneous theory of mind (ToM): An fMRI multi-study investigation.

There is a major debate in the theory of mind (ToM) field, concerning whether spontaneous and explicit ToM are based on the same or two distinct cognitive systems. While extensive research on the neural correlates of explicit ToM has demonstrated involvement of the temporo-parietal junction (TPJ) and the medial prefrontal cortex (mPFC), few studies investigated spontaneous ToM, leaving some open questions. Here, we implemented a multi-study approach by pooling data from three fMRI studies to obtain a larger sample to increase power and sensitivity to better define the neurocognitive mechanisms underlying spontaneous ToM. Participants watched videos in which an agent acquires a true or false belief about the location of a ball. Thus, the belief of the agent and that of the participant could either match or differ. Importantly, participants were never asked to consider the belief of the agent and were only instructed to press a button when they detected the presence of the ball after an occluder fell at the end of each video. By analysing the blood-oxygen level dependent signal during the belief formation phase for false versus true beliefs, we found a cluster of activation in the right, and to a lesser extent, left posterior parietal cortex spanning the TPJ, but no mPFC activation. Region of interest (ROI) analysis on bilateral TPJ and mPFC confirmed these results and added evidence to the asymmetry in laterality of the TPJ in spontaneous ToM. Interestingly, the whole brain analysis, supported by an overlap with brain maps, revealed maximum activation in areas involved in visuospatial working memory and attention switching functions, such as the supramarginal gyrus, the middle temporal gyrus, and the inferior frontal gyrus. By contrast, evidence for the presence of brain-behaviour correlations was mixed and there was no evidence for functional connectivity between the TPJ and mPFC. Taken together, these findings help clarifying the brain system supporting spontaneous ToM.

Automatic imitation of multiple agents: A computational model.

There is accumulating evidence that the actions of others are represented in the motor system, leading to automatic imitation. However, whereas early work focused mainly on the effects of observing a single agent, recent studies indicate that the actions of multiple agents can be represented simultaneously. Yet, theorizing has lagged behind. The current study extends the dual-route model of automatic imitation to include multiple agents, and demonstrates, in five simulation studies, that the extended model is able to capture four critical multi-agent effects. Importantly, however, it was necessary to augment the model with a control mechanism regulating response inhibition based on the number of observed actions. Furthermore, additional simulation indicated that this mechanism could be driven by response conflict. Together, our results demonstrate how theories of automatic imitation can be extended from single- to multi-agent settings. As such, they constitute an important step towards a mechanistic understanding of social interaction beyond the dyad.

Reaction time indices of automatic imitation measure imitative response tendencies.

In his review, Ramsey (2018) argues that it is currently unclear what reaction time indices of automatic imitation measure due to lacking research on their validity and domain-specificity. In our commentary, we argue that this conclusion is based on two misconceptions, namely that automatic imitation was designed as a laboratory measure of motor mimicry and that psychometric approaches to validity can readily be applied to experimental settings. We then show that reaction time indices of automatic imitation measure covert imitative response tendencies. Furthermore, while irrelevant for their validity, we argue that these indices are associated with some, but not necessarily all, types of overt imitation. Finally, we argue that mapping out the brain networks does not suffice to understand the brain processes underlying imitative control.

The role of sensorimotor processes in social group contagion.

Although it is well known that action observation triggers an imitative response, not much is known about how these responses develop as a function of group size. Research on social contagion suggests that imitative tendencies initially increase but then stabilize as groups become larger. However, these findings have mainly been explained in terms of interpretative processes. Across seven experiments (N = 322), the current study investigated the contribution of sensorimotor processes to social group contagion by looking at the relation between group size and automatic imitation in a task that involved minimal interpretation. The results of Experiments 1-2 revealed that automatic imitation increased with group size according to an asymptotic curve on congruent trials but a linear curve on incongruent trials. The results of Experiments 3-7 showed that the asymptote on congruent trials disappeared when no control was needed, namely in the absence of incongruent trials. This suggests that the asymptote in the relation between group size and automatic imitation can be explained in terms of strategic control mechanisms that aim to prevent unintended imitative responses. The findings of the current study are in close correspondence with previous research in the social domain and as such support the hypothesis that sensorimotor processes contribute to the relation between group size and social contagion.

Emotion regulation across childhood and adolescence: evidence for a maladaptive shift in adolescence.

Dysfunctional emotion regulation is an important predictor of psychopathology. Although many clinical programs focus on emotion regulation skills, the successful application of these programs in children and adolescents requires knowledge on the normative use of emotion regulation strategies over age. To this end, the current cross-sectional study examined changes in emotion regulation throughout childhood and adolescence. The use of seven adaptive and five maladaptive emotion regulation strategies was measured with the FEEL-KJ in a representative sample (N = 1397) of Dutch children and adolescents between 8 and 18 years old. Overall, the results indicated reduced use of adaptive strategies and increased use of maladaptive strategies in participants between 12 and 15 years old compared with younger or older participants. The findings of the current study indicate that adolescence is characterized by a maladaptive shift in emotion regulation. Given that the continued use of dysfunctional emotion regulation plays an important role in the development and maintenance of psychopathology, these results highlight the importance of prevention and treatment programs focused on emotion regulation to shield vulnerable adolescents against mental illness.

Top-down biological motion perception does not differ between adults scoring high versus low on autism traits.

The perception of biological motion is an important social cognitive ability. Models of biological motion perception recognize two processes that contribute to the perception of biological motion: a bottom-up process that binds optic-flow patterns into a coherent percept of biological motion and a top-down process that binds sequences of body-posture 'snapshots' over time into a fluent percept of biological motion. The vast majority of studies on autism and biological motion perception have used point-light figure stimuli, which elicit biological motion perception predominantly via bottom-up processes. Here, we investigated whether autism is associated with deviances in the top-down processing of biological motion. For this, we tested a sample of adults scoring low vs high on autism traits on a recently validated EEG paradigm in which apparent biological motion is combined with frequency tagging (Cracco et al., 2022) to dissociate between two percepts: 1) the representation of individual body postures, and 2) their temporal integration into movements. In contrast to our hypothesis, we found no evidence for a diminished temporal body posture integration in the high-scoring group. We did, however, find a group difference that suggests that adults scoring high on autism traits have a visual processing style that focuses more on a single percept (i.e. either body postures or movements, contingent on saliency) compared to adults scoring low on autism traits who instead seemed to represent the two percepts included in the paradigm in a more balanced manner. Although unexpected, this finding aligns well with the autism literature on perceptual stability.

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.

An EEG frequency tagging study on biological motion perception in children with DCD.

BACKGROUND: The perception of biological motion requires accurate prediction of the spatiotemporal dynamics of human movement. Research on Developmental Coordination Disorder (DCD) suggests deficits in accurate motor prediction, raising the question whether not just action execution, but also action perception is perturbed in this disorder. AIMS: To examine action perception by comparing the neural response to the observation of apparent biological motion in children with and without DCD. METHODS AND PROCEDURES: Thirty-three participants with and 33 without DCD, matched based on age (13.0 ± 2.0), sex and writing hand, observed sequences of static body postures that showed either fluent or non-fluent motion, in which only the fluent condition depicted apparent biological motion. Using a recently validated paradigm combining EEG frequency tagging and apparent biological motion (Cracco et al., 2023), the perception of biological motion was contrasted with the perception of individual body postures. OUTCOMES AND CONCLUSIONS: Children with DCD did not show reduced sensitivity to apparent biological motion compared with typically developing children. However, the DCD group did show a reduced brain response to repetitive visual stimuli, suggesting altered predictive processing in the perceptual domain in this group. Suggestions for further research on biological motion perception in DCD are identified.

The role of objecthood and animacy in apparent movement processing.

Although the ability to detect the actions of other living beings is key for adaptive social behavior, it is still unclear if biological motion perception is specific to human stimuli. Biological motion perception involves both bottom-up processing of movement kinematics ('motion pathway') and top-down reconstruction of movement from changes in the body posture ('form pathway'). Previous research using point-light displays has shown that processing in the motion pathway depends on the presence of a well-defined, configural shape (objecthood) but not necessarily on whether that shape depicts a living being (animacy). Here, we focused on the form pathway. Specifically, we combined electroencephalography (EEG) frequency tagging with apparent motion to study how objecthood and animacy influence posture processing and the integration of postures into movements. By measuring brain responses to repeating sequences of well-defined or pixelated images (objecthood), depicting human or corkscrew agents (animacy), performing either fluent or non-fluent movements (movement fluency), we found that movement processing was sensitive to objecthood but not animacy. In contrast, posture processing was sensitive to both. Together, these results indicate that reconstructing biological movements from apparent motion sequences requires a well-defined but not necessarily an animate shape. Instead, stimulus animacy appears to be relevant only for posture processing.

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.

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.

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.