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.

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.

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.

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.

How does simulation of an observed external body state influence categorisation of an easily graspable object?

Several works have provided evidence of a resonant motor effect while observing a hand interacting with painful stimuli. The aim of this work is to show that participants are sensitive to the observation of an injured hand when they have to categorise an easily graspable object with their own hand. In Experiment 1, participants indicated whether or not photographs of objects (graspable or non-graspable, left or right oriented) could be grasped with their dominant hand, by tapping a key on a keyboard. Target objects were preceded by primes consisting of photographs of hands (injured vs healthy) in a grasping posture (power grasp). Experiment 2 consisted of two phases: In the first phase, participants had to categorise square or circle shapes. After their response (Group 1: tapping a key vs Group 2: constricting a hand grip), photograph of two types of hand (injured vs healthy) was displayed on the computer screen. In the second phase, participants had to indicate whether objects could be easily grasped with their dominant hand. Target objects were preceded by primes (square and circle) as shown in the first phase. Results show that response times were slower when the graspable target objects were right oriented and preceded by the photograph or a geometric shape associated with an injured hand. This response delay was accentuated in the handgrip condition. These results highlight that the view of an injured hand activates motor programme and pain mechanisms associated with participants relative to the consequences of the simulated grasping action.