Emilie Caspar

The relationship between human agency and embodiment

Humans regularly feel a sense of agency (SoA) over events where the causal link between action and outcome is extremely indirect. We have investigated how intermediate (here, a robotic hand) events that intervene between action and outcome may alter SoA, using intentional binding measures. The robotic hand either performed the same movement as the participant (active congruent), or performed a similar movement with another finger (active incongruent). Binding was significantly reduced in the active incongruent relative to the active congruent condition, suggesting that altered embodiment influences SoA. However, binding effects were comparable between a condition where the robot hand made a congruent movement, and conditions where no robot hand was involved, suggesting that intermediate and embodied events do not reduce SoA. We suggest that human sense of agency involves both statistical associations between intentions and arbitrary outcomes, and an effector-specific matching of sensorimotor means used to achieve the outcome.

Coercion Changes the Sense of Agency in the Human Brain

Summary People may deny responsibility for negative consequences of their actions by claiming that they were “only obeying orders.” The “Nuremberg defense” offers one extreme example, though it is often dismissed as merely an attempt to avoid responsibility. Milgram’s classic laboratory studies reported widespread obedience to an instruction to harm, suggesting that social coercion may alter mechanisms of voluntary agency, and hence abolish the normal experience of being in control of one’s own actions. However, Milgram’s and other studies relied on dissembling and on explicit measures of agency, which are known to be biased by social norms. Here, we combined coercive instructions to administer harm to a co-participant, with implicit measures of sense of agency, based on perceived compression of time intervals between voluntary actions and their outcomes, and with electrophysiological recordings. In two experiments, an experimenter ordered a volunteer to make a key-press action that caused either financial penalty or demonstrably painful electric shock to their co-participant, thereby increasing their own financial gain. Coercion increased the perceived interval between action and outcome, relative to a situation where participants freely chose to inflict the same harms. Interestingly, coercion also reduced the neural processing of the outcomes of one’s own action. Thus, people who obey orders may subjectively experience their actions as closer to passive movements than fully voluntary actions. Our results highlight the complex relation between the brain mechanisms that generate the subjective experience of voluntary actions and social constructs, such as responsibility.

New frontiers in the rubber hand experiment: when a robotic hand becomes one’s own

The rubber hand illusion is an experimental paradigm in which participants consider a fake hand to be part of their body. This paradigm has been used in many domains of psychology (i.e., research on pain, body ownership, agency) and is of clinical importance. The classic rubber hand paradigm nevertheless suffers from limitations, such as the absence of active motion or the reliance on approximate measurements, which makes strict experimental conditions difficult to obtain. Here, we report on the development of a novel technology—a robotic, user- and computer-controllable hand—that addresses many of the limitations associated with the classic rubber hand paradigm. Because participants can actively control the robotic hand, the device affords higher realism and authenticity. Our robotic hand has a comparatively low cost and opens up novel and innovative methods. In order to validate the robotic hand, we have carried out three experiments. The first two studies were based on previous research using the rubber hand, while the third was specific to the robotic hand. We measured both sense of agency and ownership. Overall, results show that participants experienced a “robotic hand illusion” in the baseline conditions. Furthermore, we also replicated previous results about agency and ownership.

The sense of agency as tracking control

Does sense of agency (SoA) arise merely from action-outcome associations, or does an additional real-time process track each step along the chain? Tracking control predicts that deviant intermediate steps between action and outcome should reduce SoA. In two experiments, participants learned mappings between two finger actions and two tones. In later test blocks, actions triggered a robot hand moving either the same or a different finger, and also triggered tones, which were congruent or incongruent with the mapping. The perceived delay between actions and tones gave a proxy measure for SoA. Action-tone binding was stronger for congruent than incongruent tones, but only when the robot movement was also congruent. Congruent tones also had reduced N1 amplitudes, but again only when the robot movement was congruent. We suggest that SoA partly depends on a real-time tracking control mechanism, since deviant intermediate action of the robot reduced SoA over the tone.

The Influence of (Dis)belief in Free Will on Immoral Behavior

One of the hallmarks of human existence is that we all hold beliefs that determine how we act. Amongst such beliefs, the idea that we are endowed with free will appears to be linked to prosocial behaviors, probably by enhancing the feeling of responsibility of individuals over their own actions. However, such effects appear to be more complex that one might have initially thought. Here, we aimed at exploring how induced disbeliefs in free will impact the sense of agency over the consequences of one’s own actions in a paradigm that engages morality. To do so, we asked participants to choose to inflict or to refrain from inflicting an electric choc to another participant in exchange of a small financial benefit. Our results show that participants who were primed with a text defending neural determinism – the idea that humans are a mere bunch of neurons guided by their biology – administered fewer shocks and were less vindictive toward the other participant. Importantly, this finding only held for female participants. These results show the complex interaction between gender, (dis)beliefs in free will and moral behavior.

Placebo-suggestion modulates conflict resolution in the Stroop Task.

Here, we ask whether placebo-suggestion (without any form of hypnotic induction) can modulate the resolution of cognitive conflict. Naïve participants performed a Stroop Task while wearing an EEG cap described as a “brain wave” machine. In Experiment 1, participants were made to believe that the EEG cap would either enhance or decrease their color perception and performance on the Stroop task. In Experiment 2, participants were explicitly asked to imagine that their color perception and performance would be enhanced or decreased (non-hypnotic imaginative suggestion). We observed effects of placebo-suggestion on Stroop interference on accuracy: interference was decreased with positive suggestion and increased with negative suggestion compared to baseline. Intra-individual variability was also increased under negative suggestion compared to baseline. Compliance with the instruction to imagine a modulation of performance, on the other hand, did not influence accuracy and only had a negative impact on response latencies and on intra-individual variability, especially in the congruent condition of the Stroop Task. Taken together, these results demonstrate that expectations induced by a placebo-suggestion can modulate our ability to resolve cognitive conflict, either facilitating or impairing response accuracy depending on the suggestion’s contents. Our results also demonstrate a dissociation between placebo-suggestion and non-hypnotic imaginative suggestion.

The Power of Suggestion: Posthypnotically Induced Changes in the Temporal Binding of Intentional Action Outcomes:

The sense of agency is the experience of initiating and controlling one’s voluntary actions and their outcomes. Intentional binding (i.e., when voluntary actions and their outcomes are perceived to occur closer together in time than involuntary actions and their outcomes) is increased in intentional action but requires no explicit reflection on agency. The reported experience of involuntariness is central to hypnotic responding, during which strategic action is experienced as involuntary. We report reduced intentional binding in a hypnotically induced experience of involuntariness, providing an objective correlate of reports of involuntariness. We argue that this reduced binding results from the diminished influence of motor intentions in the generation of the sense of agency when beliefs about whether an action is intended are altered. Thus, intentional binding depends on awareness of intentions. This finding shows that changes in metacognition of intentions affect perception.

“Free will”: are we all equal? A dynamical perspective of the conscious intention to move

Abstract In their seminal (1983) study, Libet and colleagues suggested that awareness of one’s intention to act has a postdictive character in that it occurs long after cerebral activity leading to action has been initiated. Crucially, Libet et al. further suggested that the time window (±200 ms) between the conscious experience of the intention to act and the action itself offers people the possibility of “vetoing” the unfolding action. This raises the question of whether there are individual differences in the duration of this “veto window” and which components of the readiness potential (RP) and the lateralized readiness potential (LRP) explain this variability. It has been reported that some psychiatric diseases lead to shorter intervals between conscious intentions and actions. However, it is unclear whether such patients suffer from impairment of the sense of volition, thus experiencing voluntary movements as involuntary, or whether voluntary inhibition of action is actually reduced, since conscious intention occurs later. We had two aims in the present paper. First, we aimed at clarifying the role of consciousness in voluntary actions by examining the relation between the duration of the veto window and impulsivity. Second, we sought to examine different components of the RP and LRP waveforms so as to attempt to explain observed variability in W judgments. Our results indicate (1) that impulsive people exhibit a shorter delay between their intention and the action than non-impulsive people, and (2) that this difference can hardly be attributed to a difference in time perception. Electroencephalography indicated that the rate of growth of the RP is relevant to explain differences in W judgments, since we observed that the RP at the moment of conscious intention is lower for people with late conscious intention than for people with early conscious intention. The onset and the intercept of these waveforms were less interpretable. These results bring new light on the role that consciousness plays in voluntary action.

What Do You Believe In? French Translation of the FAD-Plus to Assess Beliefs in Free Will and Determinism and Their Relationship with Religious Practices and Personality Traits

The influence of (dis)belief in free will on prosocial behaviors and sense of control has attracted considerable interest over the last few years. The provision of relevant research tools to assess beliefs in free will and determinism for the community thus becomes a central endeavour. However, no relevant validated questionnaires are currently available to the French language community. Therefore, the present study was aimed at providing a valid French translation of the FAD-plus (Paulhus & Carey, 2011), a questionnaire built to assess people’s beliefs in Free will and Determinism. Exploratory factor analysis of the data obtained in Sample 1 revealed a four factor model. Confirmatory factor analyses on the basis of Sample 2 data were conducted to compare the theoretical model advanced by Paulhus and Carey’s versus the model obtained in Sample 1. With only but a few modifications as compared to the original questionnaire, the questionnaire that we here propose appears to constitute a reliable tool for the French language community. We also examined the relationship between beliefs in free will, determinism and religious practices. We found that the more people are engaged in religious practices, the more they believe in determinism and in the inevitability of their future.

Human body schema exploration: Analyzing design requirements of Robotic Hand and Leg Illusions

Understanding the integration of user-proximal robots in the body schema of their human users has a distinct potential to improve human-robot interaction. Robotic devices can help to investigate the psychological fundamentals of body schema integration. While the Rubber Hand Illusion experiment indicates how artifacts can be perceived as a part of the own body, it relies on a passive limb that does not perform motions during the examinations. Novel setups aim at Robotic Hand/Leg Illusions induced by robotic devices which imitate human motions. Although such devices distinctly extend experimental possibilities, their design is rather proprietary and unstructured up to now. This paper analyzes the requirements of robotic hand and leg illusion setups based on systematic discussion of a multidisciplinary team of researchers from engineering and psychology. In a comparative study, requirements are collected and structured, their similarities and differences are determined, and the most important ones are extracted yielding design implications. The requirements with the highest priority are setup characteristics that concern the occurrence and quality of the illusion, i.e., hiding the real limb, anatomical plausibility, visual appearance, temporal delay, and software-controlled experimental conditions. Based on the results, the design of future robotic devices for the exploration of human body schema integration might be guided and supported.