The Simon effect under reversed visual feedback.

Our aim was to study the processes involved in the spatial coding of the body during actions producing multiple simultaneous effects. We specifically aimed to challenge the intentional-based account, which proposes that the effects used to code responses are those deemed relevant to the agent's goal. Accordingly, we used a Simon paradigm (widely recognized as a suitable method to investigate the spatial coding of responses) combined with a setup inducing a multimodal discrepancy between visual and tactile/proprioceptive effects (known to be crucial for body schema construction and action control). To be more precise, the setup allowed to horizontally reverse the visual effects of the hands compared to the tactile/proprioceptive effects (e.g., the right hand was seen as being on the left). In Experiment 1, the visual effects were not reversed. However, in Experiment 2, the visual effects were reversed, and the task emphasized the relevance of these effects to the participants. In Experiment 3, the visual effects were also reversed, but the task emphasized the relevance of tactile/proprioceptive effects. A Simon effect, based on the location of the tactile/proprioceptive effects, was observed in Experiments 1 and 3. However, in Experiment 2, the Simon effect was partially driven by the location of the visual effects. These findings collectively support that the agent's intention plays a prominent role in the representation of their body during action. This work also suggests a promising avenue for research in linking action and body representations.

Mirror game as a tool to influence interpersonal spontaneous behavior after performance.

Mirror game (MG) is an exercise in which participants imitate each other. Our study explored its spontaneous behavioral consequences after performance. In a baseline (BL) phase, two participants performed a joint Simon task. Then, they performed a lure task during which we measured the interpersonal distance they spontaneously adopted. The BL phase was followed by two phases (in counterbalanced order). The MG phase started with a MG, before a procedure like the BL phase. The individual movement (IM) phase started with movements performed alone before a procedure like the BL phase. Interpersonal distance analysis suggested that MG enhanced spontaneous approach toward the partner, whereas IM induced spontaneous avoidance. Moreover, the joint Simon effect (JSE) tended to be smaller after IM, suggesting a decreasing inclination to integrate the partner's response in one's own action plan. Furthermore, in IM phase, JSE decreased as interpersonal distance increased.

The size coding of responses: The size of switches and the force feedback.

We aimed to understand which factors have a functional role in the size coding of responses, either the size of the switches or the force required to trigger each switch. This question is of relevance because it allows a better understanding of processes underlying action coding. In each trial, participants saw a small or large object. Depending on its colour, the participants had to press one of two switches. In the "size" condition, the response device consisted of two switches of different visual size, but both required the same amount of force. In the "force-feedback" condition, the response device consisted in two switches of identical visual size, but one switch required more force than the other. We found a compatibility effect in the "size," not in the "force-feedback" condition, supporting that the size-coding of responses would be due to the size of the switches.

Manipulable objects can potentiate pointing and unusual grasping besides habitual grasping behaviors.

People are faster to perform a precision grip when they see a cherry (i.e., a small graspable object) than to perform a power grip, and the reverse holds true when they see an apple (i.e., a large graspable object). This potentiation effect supports that object representations could include motor components that would be simulated when a graspable object is seen. However, the nature of these motor components remains unclear. The embodied account posits that seeing an object only potentiates the most frequent actions associated with it (i.e., usual actions). In contrast, the size-coding account posits that seeing an object potentiates any actions associated to spatial codes compatible with those associated to the objects. We conducted three experiments to disentangle these two alternative accounts. We especially varied the nature of the responses while participants saw either large or small graspable objects. Our results showed a potentiation effect when participants performed the usual grasping actions (Experiment 1: power and precision grip) but also when they performed unusual grasping actions (Experiment 2: grasping between the thumb and little finger) and even when they had to perform non-grasping actions (Experiment 3: pointing actions). By supporting the size-coding account, our contribution underlines the need for a better understanding of the nature of the motor components of object representations and for using a proper control condition (i.e., pointing action) before arguing that the embodied account convincingly explains the potentiation effect of grasping behaviors.

Anticipating the magnitude of response outcomes can induce a potentiation effect for manipulable objects.

Merely seeing large objects (e.g., apples) potentiates power grip whereas seeing small objects (e.g., strawberries) potentiates precision grip. According to the embodied cognition account, this potentiation effect reflects automatic access to object representation, including the grip usually associated with the object. Alternatively, this effect might be due to an overlap between magnitude codes used to code manipulable objects and magnitude codes used to code responses outcomes. In Experiment 1, participants saw objects usually grasped with a power or precision grip and had to press keys either with their forefinger or with their palm, each response generating a low or high tone (i.e., a large vs. small perceptual outcome, respectively). Tones were automatically delivered by headphones after the responses have been made in line with the ideomotor theories according to which voluntary actions are carried out due to the anticipation of their outcomes. Consistent with the magnitude-coding hypothesis, response times were shorter when the object and the anticipated response outcome were of the same magnitude than when they were not. These results were also consistent with a between-experiment analysis. In Experiments 2 and 3, we investigated to what extent removing or switching the outcomes during the experiment influence the potentiation effect. Our results support that the potentiation effect of grasping behaviours could be due to the compatibility between magnitude codes rather than to the involvement of motor representations. Our results also suggest a spontaneous use of the magnitude of response outcomes to code responses, as well as the flexibility of this coding processes when responses outcomes are altered.

The visual size of graspable objects is needed to induce the potentiation of grasping behaviors even with verbal stimuli.

Merely perceiving objects usually grasped with a power or a precision grip (e.g., an apple vs. a cherry) potentiate power-grip and precision-grip responses, respectively. According to the size-coding account, this potentiation effect is due to the compatibility between size codes associated with both stimuli and responses, rather than to the simulation of motor information stored at a conceptual level (i.e., the embodied account). At the stimulus level, size-coding would occur, because objects associated with a power grip are usually presented in a larger visual size than objects associated with a precision grip. However, this explanation is challenged by results, showing that reading nouns of objects associated with power or precision grip also leads to potentiation effects, even though the visual size of the displayed object is no longer perceived. Therefore, we designed three experiments to better understand this word-based potentiation effect and to investigate whether it relies on size codes. Our results showed a word-based potentiation effect only when the object nouns were interleaved with pictures depicting the objects in their typical visual size. We discuss the contributions of these results for both the size-coding account and the embodied account of the potentiation effect of grasping behaviors.

The diversity of possible constitutive components in cognitive neurosciences.

I aim to discuss which constitutive components are essential for explaining how the mind works. Rather than focusing on some specific components, I emphasize their diversity. Thus, I seek to complement the recent mechanistic proposal by underscoring that researchers should remain open-minded about which constitutive components should be investigated.

The prediction-confirmation account of the sense of body ownership: Evidence from a rubber hand illusion paradigm.

We investigated the contribution of multisensory predictions to body ownership, and beyond, to the integration of body-related signals. Contrary to the prevailing idea, according to which, to be integrated, cues necessarily have to be perceived simultaneously, we instead proposed the prediction-confirmation account. According to this account, a perceived cue can be integrated with a predicted cue as long as both signals are relatively simultaneous. To test this hypothesis, a standard rubber hand illusion (RHI) paradigm was used. In the first part of each trial, the illusion was induced while participants observed the rubber hand being touched with a paintbrush. In the subsequent part of the trial, (i) both rubber hand and the participant's real hand were stroked as before (i.e., visible/synchronous condition), (ii) the rubber hand was not stroke anymore (i.e., visible/tactile-only condition), or (iii) both rubber hand and the participant's real hand were synchronously stroked while the location where the rubber hand was touched was occulted (i.e., occulted/synchronous condition). However, in this latter condition, participants still perceived the approaching movement of the paintbrush. Thus, based on this visual cue, the participants can properly predict the timepoint at which the tactile cue should occur (i.e., visuotactile predictions). Our major finding was that compared with the visible/tactile-only condition, the occulted/synchronous condition did not exhibit a decrease of the RHI as in the visible/synchronous condition. This finding supports the prediction-confirmation account and suggests that this mechanism operates even in the standard version of the RHI.

Color perception involves color representations firstly at a semantic level and then at a lexical level.

Studies and models have suggested that color perception first involves access to semantic representations of color. This result leads to two questions: (1) is knowledge able to influence the perception of color when associated with a color? and (2) can the perception of color really involve only semantic representations? We developed an experiment where participants have to discriminate the color of a patch (yellow vs. green). The target patch is preceded either by a black-and-white line drawing or by a word representing a natural object associated with the same or a different color (banana vs. frog). We expected a priming effect for pictures because, with a 350-ms SOA, they only involve access to semantic representations of color, whereas words seem only elicit an access to lexical representations. As expected, we found a priming effect for pictures, but also for words. Moreover, we found a general slowdown of response times in the word-prime-condition suggesting the need of an additional processing step to produce priming. In a second experiment, we manipulated the SOA in order to preclude a semantic access in the word-prime-condition that could explain the additional step of processing. We also found a priming effect, suggesting that interaction with perception occurs at a lexical level and the additional step occurs at a color perception level. In the discussion, we develop a new model of color perception assuming that color perception involves access to semantic representations and then access to lexical representations.

Beyond grasping: Syllables processing influences mere manual keypress.

We aimed to better understand the link between vocalization and grasping. We especially test whether neurocognitive processes underlying this interaction are not grasping specific. To test this hypothesis, we used the procedure of a previous experiment, showing that silently reading the syllable KA and TI can facilitate power- and precision-grip responses, respectively. In our experiment, the participants have to silently read the syllable KA or TI but, according to the color of the syllables, have merely to press a large or small switch (we removed the grasping component of responses). Responses on the large switch were faster when the syllable KA was read compared with TI and conversely for the responses carried out on the small switch. This result supports that the influence of vocalization is not restricted to grasping responses, and, in addition, it supports an alternative, non-grasping-specific model of interactions between vocalization and grasping.

The visual size is enough to automatically induce the potentiation of grasping behaviours.

Seeing objects usually grasped with a power or a precision grip (e.g., an apple vs a cherry) potentiates power- and precision-grip responses, respectively. An embodied account suggests that this effect occurs because object conceptual representations would lie on a motor simulation process. A new account, named the size-coding account, argues that this effect could be rather due to an overlapping of size codes used to represent both manipulable objects and response options. In this article, we investigate whether this potentiation effect could be merely due to a low-level visual feature that favours a size-coding of stimuli: the visual size in which objects are presented. Accordingly, we conducted two experiments in which we presented highly elementary and non-graspable stimuli (i.e., ink spots) either large or small rather than graspable objects. Our results showed that the mere visual size automatically potentiates power- and precision-grip responses that are in line with the size-coding account of the potentiation effect of grasping behaviours. Moreover, these results appeal to improve the methodological control of the size of stimuli especially when researchers try to support the embodied account.

Size coding of alternative responses is sufficient to induce a potentiation effect with manipulable objects.

The mere perception of manipulable objects usually grasped with a power-grip (e.g., an apple) or a precision-grip (e.g., a cherry) potentiate power-grip- and precision-grip-responses, respectively. This effect is seen as to be driven by automatic access of the representation of manipulable objects that includes a motor representation of usually performed grasping behaviors (i.e., the embodied view). Nevertheless, a competing account argues that this effect could be due to an overlapping of size codes used to represent both manipulable objects and response options. Indeed, objects usually grasped with a power- and a precision-grip (e.g., an apple vs. a cherry) could be coded as large- and small-objects, respectively; and power- and precision-grip responses as large- and small-responses, respectively. We conducted 4 experiments to test this hypothesis. In Experiment 1, the response device usually used in studies reporting a potentiation effect is fixed horizontally (the grasping component of responses was removed). We instructed participants to press the small-switch with their index-digit and the large-switch with their palm-hand. In line with the size-coding-hypothesis, responses on the small-switch performed with the index-digit led to shorter RTs when objects usually associated with a precision-grip (e.g., a cherry) were presented compared to objects usually associated with a power-grip (e.g., an apple). A reverse pattern was obtained for responses on the large-switch performed with the palm-hand. In Experiments 2, 3 and 4, we went further by investigating which factors of Experiment 1 allow the size coding of responses: the size of switch and/or the size of the effector part used. Data confirmed the critical involvement of the size of switches and the possible involvement of the size of the effector part used. Thus, data support the possibility that the potentiation of grasping is due to a compatibility/incompatibility between size codes rather than involving motor representations of usually performed grasping behaviors as advocated in several embodied views. Moreover, data support the possibility that responses are coded thanks to a size code that extends the Theory of Event Coding.

Motor simulation in tool-use effect on distance estimation: A replication of Witt and Proffitt (2008).

Witt and Proffit (Human Perception and Performance, 34 (6), 1479-1492, 2008) hypothesized that when people intend to reach a target, they run a motor simulation allowing them to anticipate potential reaching constraints and outcomes, which in turn affects spatial perception. They reported that participants estimated targets to be closer to them when they intended to use a reach-extending tool, but only when they did not perform a concurrent motor task. The authors concluded that the concurrent motor task prevented the simulation of tool-use and its effect on perception. Reported here is a replication that extends their work through an additional control group and a larger sample size. Our results failed to support either the role of motor simulation in the tool-use effect on distance estimation or the tool-use effect itself. Moreover, a reanalysis of Witt and Proffitt's data suggested that they should have been more nuanced in their own conclusions. Further replications are needed in order to elucidate the existence, nature, boundary conditions, and underlying mechanisms of the action constraint effects on space perception.

Pre-Calibrated Visuo-Haptic Co-Location Improves Execution in Virtual Environments.

A common approach to visio-haptic human-machine interfaces adopts a simpler design by shifting grounded force feedback away from the virtual scene. The alternative design favors intuitiveness by displaying visual and grounded force feedback at the same location (i.e. visuo-haptic co-location) but requires a sensibly more complex implementation and a tedious kinematic conception. The benefits of one approach over the other had not been fully investigated. Notably, (i) while users seem to better operate under co-located condition, it's not always the case. (ii) In the case of a desktop interface, the cost of a complex implementation to achieve co-location is challenged. We aim here to resolve (i) by conducting a user-centered experiment in which participants performed two generic tasks in co-located and delocated configurations, and comparing their performances. Additionally, we intend to fill the gap (ii) by testing a design without continuous head tracking, i.e., with static co-location. Participants' performances are assessed in terms of execution time, accuracy and force variation, while their subjective experiences are collected via a survey. Findings indicate that co-located configurations lead to shorter execution times, more accurate motions, better management of forces and are largely preferred by users, even when the co-location is pre-calibrated statically.

A continuous mapping between space and valence with left- and right-handers.

In this research, we examined whether emotional valence could correspond to a continuous lateral bias in space, according to a mental metaphor that establishes the mapping between a concrete domain (space) and an abstract one (valence). Because acting with one's dominant hand is associated with fluency and positive valence (the bodily specificity hypothesis, or BSH), we asked strong right- and left-handers to perform two spatial location tasks using emotional faces with seven levels of valence. We hypothesized and showed through two studies that, according to the BSH, extreme valenced stimuli (as compared to moderate and weak ones) would be located more at the extremity of a horizontal line, according to the correspondences between handedness and the different valences of the stimuli. This research establishes that spatial and continuous mapping of emotions was obtained while controlling for motivational direction.