Embodied perception of reachable space: how do we manage threatening objects?

Immorality backward, morality forward? Metaphorical morality in Chinese-English bilinguals

This study explored whether instructing participants to make forward or backward joystick movements in response to morality words is consistent with the conceptual metaphor MORAL IS MOVING FORWARD/IMMORAL IS MOVING BACKWARD in Chinese-English bilinguals' first and second languages. Chinese-English bilinguals were instructed to categorize words as moral or immoral while moving a joystick in a compatible block (moral-forward, immoral-backward) and an incompatible block (moral-backward, immoral-forward). The results revealed three main conclusions: First, participants showed faster categorization of immoral words when their responses involved backward joystick movements compared to forward joystick movements. Second, participants also demonstrated a slightly faster categorization of moral words when their responses involved backward joystick movements compared to forward joystick movements. Third, Chinese morality words were categorized faster overall than English morality words. However, despite a slightly larger effect size observed in L1, the action compatibility effects for morality words exhibited a similar pattern across both languages. In sum, bilinguals showed shared access to the IMMORAL IS MOVING BACKWARD conceptual metaphor across both L1 and L2, but they did not access the MORAL IS MOVING FORWARD conceptual metaphor in either L1 or L2. This study provides new evidence supporting the conceptual metaphor theory.

The influence of threat on visuospatial perception, affordances, and protective behaviour: A systematic review and meta-analysis

Perception has been conceptualised as an active and adaptive process, based upon incoming sensory inputs, which are modified by top-down factors such as cognitions. Visuospatial perception is thought to be scaled based on threat, with highly threatening objects or contexts visually inflated to promote escape or avoidance behaviours. This meta-analytical systematic review quantified the effect and evidence quality of threat-evoked visuospatial scaling, as well as how visuospatial scaling relates to affordances (perceived action capabilities) and behavioural avoidance/escape outcomes. Databases and grey literature were systematically searched inclusive to 10/04/24. Studies were assessed with a customised Risk of Bias form and meta-analysis was performed using a random-effects model. 12,354 records were identified. Of these, 49 experiments (n = 3027) were included in the review. There was consistent evidence that threat the of height influenced contextual perception (g = 0.66, 95% CI: 0.45, 0.88) and affordances (g = -0.43, 95% CI: -0.84, -0.03). Threatening objects were viewed as larger (g = 0.76, 95% CI: 0.26, 1.26) and as closer (g = 0.30, 95% CI: 0.17, 0.42). Bodily threat (pain) yielded conflicting effects on visuospatial perception/affordances. We conclude that threat may influence visuospatial perception and affordances. However, since behavioural measures were poorly reported, their relationship with visuospatial perception/affordances remains elusive.

Perception of interpersonal distance and social distancing before and during COVID-19 pandemic

Since COVID-19 is easily transmitted among people in close physical proximity, the focus of epidemiological policy during the COVID-19 crisis included major restrictions on interpersonal distance. However, the way in which distance restrictions affected spatial perception is unclear. In the current study, we examined interpersonal distance preferences and perceptions at three time points: pre-pandemic, early post-pandemic, and late post-pandemic. The results indicate that following the pandemic outbreak, people perceived others as farther away than they actually were, suggesting that the distance restrictions were associated with an enlargement of perceived interpersonal distance. Interestingly, however, people maintained the same distance from one another as before the outbreak, indicating no change in actual distance behavior due to the risk of infection. These findings suggest that COVID-19 was associated with a change in the way distance is perceived, while in practice, people maintain the same distance as before. In contrast, COVID-related anxiety predicted both a preference for maintaining a greater distance and a bias toward underestimating perceived distance from others. Thus, individuals who were highly fearful of COVID-19 perceived other people to be closer than they actually were and preferred to maintain a larger distance from them. The results suggest that subjective risk can lead to an increased perception of danger and a subsequent change in behavior. Taken together, even when behaviors should logically change, the decision-making process can be based on distorted perceptions. This insight may be used to predict public compliance.

Motor inhibition impacts the motor interference effect of dangerous objects based on a prime-target grasping consistency judgment task

Whether motor inhibition impacts the motor interference effect of dangerous objects is controversial. Previous studies have manipulated task type and found that dangerous objects elicited increased motor inhibition compared to safe objects in the reachability judgment task but not in the categorization task. However, it was still unclear why motor inhibition was reduced for dangerous objects in the categorization task. We speculated that the activation strength of object affordance might modulate the occurrence of motor inhibition. To test this hypothesis, the present study designed a prime-target grasping consistency judgment task and manipulated target grips (power grip vs. precision grip), target dangerousness (dangerous vs. safe), and Go/NoGo (Go vs. NoGo). The results showed that under the condition of high activation strength of the target affordance (i.e., power grip targets), processing dangerous targets evoked increased motor inhibition (reflected by a more negative frontal N2 component) compared to safe targets and produced a motor interference effect in reaction time (RT). In contrast, under the condition of low target affordance activation strength (i.e., precision grip targets), processing dangerous targets facilitated RT compared to safe targets, with no difference found between the dangerous and safe conditions in the frontal N2 component. Furthermore, compared to safe objects, dangerous objects attracted more attention and recruited more cognitive resources to select appropriate responses to them. This study extended the findings of previous studies on the motor interference effect by highlighting the importance of activation strength for eliciting motor inhibition based on the prime-target consistency judgment task.

Object coding in peripersonal space depends on object ownership

Previous studies have shown that objects located in the peripersonal space (PPS) receive enhanced attention, as compared with extrapersonal space (EPS), However, most objects in the environment belong to someone in particular and how object ownership influences object coding in relation to PPS representation is still unclear. In the present study, after having chosen their own mug, participants performed a reachability judgement task of self-owned and other-owned mugs presented at different distances while facing a virtual character. This task was followed, on each trial, by a localisation task in which participants had to indicate where the mug, removed from view, was previously located. The two tasks were separated by a 900-ms visual mask during which the virtual character was unnoticeably shifted by 3° to evaluate the spatial frame-of-reference used. The results showed that self-owned mugs were processed faster than other-owned mugs, but only when located in the PPS. Furthermore, reachability judgements were biased for self-owned mugs, leading to an extension of the PPS representation, especially for participants with a high score on the fantasy scale of Interpersonal Reactivity Index (IRI). Finally, the virtual character shift altered the localisation performance but only for the distant mugs, suggesting a progressive shift from egocentric to allocentric frame-of-reference when moving from the PPS to EPS, irrespective of object ownership. Overall, our data reveal that the representations of ownership and PPS interact to facilitate the processing of manipulable objects, to an extent that depends on individual sensitivity to the social presence of others.

Paying attention to the outcome of others' actions has dissociated effects on observer's peripersonal space representation and exploitation

The representation of peripersonal space (PPS representation) and the selection of motor actions within it (PPS exploitation) are influenced by action outcomes and reward prospects. The present study tested whether observing the outcome of others' actions altered the observer's PPS representation and exploitation. Participants (observers) performed a reachability-judgement task (assessing PPS representation) before and after having observed a confederate (actors) performing a stimuli-selection task on a touch-screen table. In the stimuli-selection task, the stimuli selected could either yield a reward or not, but the probability to select a reward-yielding stimulus was biased in space, being either 50%, 25% or 75% in the actor's proximal or distal space. After the observation phase, participants performed the stimuli-selection task (assessing PPS exploitation), but with no spatial bias in the distribution of reward-yielding stimuli. Results revealed an effect of actors' actions outcome on observers' PPS representation, which changed according to the distribution of reward-yielding stimuli in the actors' proximal and distal spaces. No significant effect of actors' actions outcome was found on observers' PPS exploitation. As a whole, the results suggest dissociated effects of observing the outcome of others' actions on PPS representation and exploitation.

Imitation of Touching Dangerous Animals Triggers Motor Inhibition in a Primed Target Grasping-Categorization Task

The present study adopted a primed target grasping-categorization task and selected pictures of animals as target stimuli to investigate whether motor inhibition influences the motor interference effect of dangerous animals. The results identified more positive P2 and P3 amplitudes accompanied by larger delta event-related synchronization in the dangerous condition than in the neutral condition, suggesting that compared to neutral animal targets, dangerous animal targets attracted increased attentional resources in early processing and that subjects recruited more cognitive resources to process dangerous animal targets than neutral animal targets. Moreover, the results identified larger theta event-related synchronization (reflecting motor inhibition) in the dangerous condition than in the neutral condition. Thus, the results suggested that prepared motor responses were inhibited to avoid touching dangerous animal targets in the current task, supporting that motor inhibition influences the motor interference effect of dangerous animals based on a primed target grasping-categorization task.

Refraining from interaction can decrease fear of physical closeness during COVID-19

Perception of peripersonal space (PPS) and interpersonal distance (IPD) has been shown to be modified by external factors such as perceived danger, the use of tools, and social factors. Especially in times of social distancing in the context of the COVID-19 pandemic, it is vital to study factors that modify PPS and IPD. The present work addresses the question of whether wearing a face mask as a protection tool and social interaction impact the perception of IPD. We tested estimated IPD in pictures at three distances: 50 cm, 90 cm, and 150 cm in both social interaction (shaking hands) and without interaction and when the two people in the pictures wore a face mask or not. Data from 60 subjects were analyzed in a linear mixed model (on both difference in distance estimation to the depicted distance and in absolute distance estimation) and in a 3 (distance: 50, 90, 150) × 2 (interaction: no interaction, shake hands), × 2 face mask (no mask, mask) rmANOVA on distance estimation difference. All analyses showed that at a distance of 50 and 90 cm, participants generally underestimated the IPD while at an IPD of 150 cm, participants overestimated the distance. This could be grounded in perceived danger and avoidance behavior at closer distances, while the wider distance between persons was not perceived as dangerous. Our findings at an IPD of 90 cm show that social interaction has the largest effect at the border of our PPS, while the face mask did not affect social interaction at either distance. In addition, the ANOVA results indicate that when no social interaction was displayed, participants felt less unsafe when depicted persons wore a face mask at distances of 90 and 150 cm. This shows that participants are on the one hand aware of the given safety measures and internalized them; on the other hand, that refraining from physical social interaction helps to get close to other persons.

Social Context and Tool Use Can Modulate Interpersonal Comfort Space

Recent research has investigated whether the representation of space around the body, in terms of reach-action (imagining of reaching another person) and comfort-social (tolerance of the other's proximity) spaces, may reflect a shared sensorimotor basis. Some studies exploiting motor plasticity induced by tool use have not observed sensorimotor identity (i.e., the same mechanisms that underlie, based on sensory information, the representation of proximal space in terms of action possibilities, goal-directed motor actions, and anticipation of the sensorimotor consequences), whereas evidence to the contrary has also emerged. Since the data are not fully convergent, here we wondered whether or not the combination of motor plasticity induced by tool use and the processing of the role of social context might reflect a similar modulation in both spaces. To this end, we conducted a randomized control trial with three groups of participants (N = 62) in which reaching and comfort distances were measured in Pre- and Post-tool-use sessions. The tool-use sessions were conducted under different conditions: (i) in the presence of a social stimulus (determining the social context) (Tool plus Mannequin group); (ii) without any stimulus (Only Tool group); (iii) in the presence of a box (Tool plus Object group) as a control condition. Results showed an extension of comfort distance in the Post-tool session of the Tool plus Mannequin group compared with the other conditions. Conversely, the reaching distance was larger after tool use than at the Pre-tool-use session, independently of the experimental conditions. Our findings suggest that motor plasticity impacts reaching and comfort spaces to different degrees; while reaching space is markedly sensitive to motor plasticity, comfort space needs qualification of social context information.

The relationship between action, social and multisensory spaces

Several spaces around the body have been described, contributing to interactions with objects (peripersonal) or people (interpersonal and personal). The sensorimotor and multisensory properties of action peripersonal space are assumed to be involved in the regulation of social personal and interpersonal spaces, but experimental evidence is tenuous. Hence, the present study investigated the relationship between multisensory integration and action and social spaces. Participants indicated when an approaching social or non-social stimulus was reachable by hand (reachable space), at a comfortable distance to interact with (interpersonal space), or at a distance beginning to cause discomfort (personal space). They also responded to a tactile stimulation delivered on the trunk during the approach of the visual stimulus (multisensory integration space). Results showed that participants were most comfortable with stimuli outside reachable space, and felt uncomfortable with stimuli well inside it. Furthermore, reachable, personal and interpersonal spaces were all positively correlated. Multisensory integration space extended beyond all other spaces and correlated only with personal space when facing a social stimulus. Considered together, these data confirm that action peripersonal space contributes to the regulation of social spaces and that multisensory integration is not specifically constrained by the spaces underlying motor action and social interactions.

Differences in office-based personal space perception between British and Korean populations

We sought to understand how the perception of personal space is influenced by different levels of social density, spatial density, and type of window-view in South Korean and United Kingdom workplaces. We employed virtual reality to simulate shared and single occupancy offices. We obtained personal space estimations using a virtual disc around the participant which could be extended and retracted, inside the simulation, to indicate perceived amount of personal space, and compared this measure to questionnaire-based estimations. We found that in both cultures participants experienced greater perceived personal space (1) when in a sparse rather than dense office and (2) having a view of the city outside the office. However, British, but not Korean, participants had significantly higher personal space estimations in single occupancy offices than in shared offices. These results suggest subtle cross-cultural differences in workplace experience, that could only be investigated using virtual reality.

During the COVID-19 pandemic participants prefer settings with a face mask, no interaction and at a closer distance

Peripersonal space is the space surrounding our body, where multisensory integration of stimuli and action execution take place. The size of peripersonal space is flexible and subject to change by various personal and situational factors. The dynamic representation of our peripersonal space modulates our spatial behaviors towards other individuals. During the COVID-19 pandemic, this spatial behavior was modified by two further factors: social distancing and wearing a face mask. Evidence from offline and online studies on the impact of a face mask on pro-social behavior is mixed. In an attempt to clarify the role of face masks as pro-social or anti-social signals, 235 observers participated in the present online study. They watched pictures of two models standing at three different distances from each other (50, 90 and 150 cm), who were either wearing a face mask or not and were either interacting by initiating a hand shake or just standing still. The observers' task was to classify the model by gender. Our results show that observers react fastest, and therefore show least avoidance, for the shortest distances (50 and 90 cm) but only when models wear a face mask and do not interact. Thus, our results document both pro- and anti-social consequences of face masks as a result of the complex interplay between social distancing and interactive behavior. Practical implications of these findings are discussed.

Emotions Modulate Affordances-Related Motor Responses: A Priming Experiment

Traditionally, research on affordances and emotions follows two separate routes. For the first time, this article explicitly links the two phenomena by investigating whether, in a discrimination task (artifact vs. natural object), the motivational states induced by emotional images can modulate affordances-related motor response elicited by dangerous and neutral graspable objects. The results show faster RTs: (i) for both neutral and dangerous objects with neutral images; (ii) for dangerous objects with pleasant images; (iii) for neutral objects with unpleasant images. Overall, these data support a significant effect of emotions on affordances. The article also proposes a brain neural network underlying emotions and affordance interplay.

The Impact of Embodiment and Avatar Sizing on Personal Space in Immersive Virtual Environments

In this paper, we examine how embodiment and manipulation of a self-avatar's dimensions - specifically the arm length - affect users' judgments of the personal space around them in an immersive virtual environment. In the real world, personal space is the immediate space around the body in which physical interactions are possible. Personal space is increasingly studied in virtual environments because of its importance to social interactions. Here, we specifically look at two components of personal space, interpersonal and peripersonal space, and how they are affected by embodiment and the sizing of a self-avatar. We manipulated embodiment, hypothesizing that higher levels of embodiment will result in larger measures of interpersonal space and smaller measures of peripersonal space. Likewise, we manipulated the arm length of a self-avatar, hypothesizing that while interpersonal space would change with changing arm length, peripersonal space would not. We found that the representation of both interpersonal and peripersonal space change when the user experiences differing levels of embodiment in accordance with our hypotheses, and that only interpersonal space was sensitive to changes in the dimensions of a self-avatar's arms. These findings provide increased understanding of the role of embodiment and self-avatars in the regulation of personal space, and provide foundations for improved design of social interaction in virtual environments.

Threat Detection in Nearby Space Mobilizes Human Ventral Premotor Cortex, Intraparietal Sulcus, and Amygdala

In the monkey brain, the precentral gyrus and ventral intraparietal area are two interconnected brain regions that form a system for detecting and responding to events in nearby “peripersonal” space (PPS), with threat detection as one of its major functions. Behavioral studies point toward a similar defensive function of PPS in humans. Here, our aim was to find support for this hypothesis by investigating if homolog regions in the human brain respond more strongly to approaching threatening stimuli. During fMRI scanning, naturalistic social stimuli were presented in a 3D virtual environment. Our results showed that the ventral premotor cortex and intraparietal sulcus responded more strongly to threatening stimuli entering PPS. Moreover, we found evidence for the involvement of the amygdala and anterior insula in processing threats. We propose that the defensive function of PPS may be supported by a subcortical circuit that sends information about the relevance of the stimulus to the premotor cortex and intraparietal sulcus, where action preparation is facilitated when necessary.

Contextual modulation of preferred social distance during the Covid-19 pandemic

Social distancing during a pandemic might be influenced by different attitudes: people may decide to reduce the risk and protect themselves from viral contagion, or they can opt to maintain their habits and be more exposed to the infection. To better understand the underlying motivating attitudes, we asked participants to indicate in an online platform the interpersonal distance from different social targets with professional/social behaviors considered more or less exposed to the virus. We selected five different social targets: a cohabitant, a friend working in a hospital, a friend landed from an international flight, a friend who is back from a cycling ride, or a stranger. In order to measure the realistic and the symbolic perceived threat, we administered the Brief 10-item COVID-19 threat scale. Moreover, in order to measure the risk attitude in different domains, the participants were also asked to fill in the Domain-Specific Risk-Taking DOSPERT scale. Results reveal a general preference for an increased distance from a stranger and the friends who are considered to be more exposed to the virus: the friend working in a hospital or landed from an international flight. Moreover, the interpersonal distance from friends is influenced by the perception of Realistic Threat measured through the Integrated Covid Threat Scale and the Health/Safety Risk Perception/Assumption as measured by the DOSPERT scale. Our results show the flexible and context-dependent nature of our representation of other people: as the social categories are not unchangeable fixed entities, the bodily (e.g., spatial) attitudes towards them are an object of continuous attunement.

Hold It Right There!

Abstract. The approach-aversion effect refers to a devaluation of approaching (vs. static) stimuli and is attributable to the fact that being approached is threatening. However, the explanation and the generalizability of this effect still remain unclear. To fill this gap, we provide a powerful test of the approach-aversion effect using Virtual Reality. Participants evaluated approaching and static virtual individuals for which we manipulated the threatening nature via their emotional facial expressions (Experiment 1), their group membership (Experiment 2), and the agency of their movements (Experiment 3). The results suggest a general approach-aversion effect which is attenuated when the self (vs. the target) initiates the movement. We thus bring convergent evidence that being approached is threatening.

Reaching Out for Food: How Food Incentives Modulate Peripersonal Space Perception

Two experiments were conducted to determine, first, whether food items influence participants’ estimations of the size of their subjective peripersonal space. It was of particular interest whether this representation is influenced by satiated/hungry states and is differentially affected by valence and calorie content of depicted stimuli. Second, event-related brain potentials (ERPs) were used, in order to obtain information about the time course of the observed effects and how they depend on the spatial location of the food pictures. For that purpose, participants had to decide whether food items shown at various distances along a horizontal plane in front of them, were reachable or not. In Experiment 1, when participants were hungry, they perceived an increase of their peripersonal space modulated by high-calorie items which were experienced as being more reachable than low-calorie items. In Experiment 2, the reachability findings were replicated and early and late components of ERPs showed an attentional enhancement in far space for food items when participants were hungry. These findings suggest that participants’ subjective peripersonal space increased while being hungry, especially for high-calorie contents. Attention also seems to be oriented more strongly to far space items due to their expected incentive-related salience, expanding the subjective representation of peripersonal space.

Defensive functions provoke similar psychophysiological reactions in reaching and comfort spaces

The space around the body crucially serves a variety of functions, first and foremost, preserving one's own safety and avoiding injury. Recent research has shown that emotional information, in particular threatening facial expressions, affects the regulation of peripersonal-reaching space (PPS, for action with objects) and interpersonal-comfort space (IPS, for social interaction). Here we explored if emotional facial expressions may similarly or differently affect both spaces in terms of psychophysiological reactions (cardiac inter-beat intervals: IBIs, i.e. inverse of heart rate; Skin Conductance Response amplitude: SCR amplitude) and spatial distance. Through Immersive Virtual Reality technology, participants determined reaching-distance (PPS) and comfort-distance (IPS) from virtual confederates exhibiting happy/angry/neutral facial expressions while being approached by them. During these interactions, spatial distance and psychophysiological reactions were recorded. Results revealed that when interacting with angry virtual confederates the distance increased similarly in both comfort-social and reaching-action spaces. Moreover, interacting with virtual confederates exhibiting angry rather than happy or neutral expressions provoked similar psychophysiological activations (SCR amplitude, IBIs) in both spaces. Regression analyses showed that psychophysiological activations, particularly SCR amplitude in response to virtual confederates approaching with angry expressions, were able to predict the increase of PPS and IPS. These findings suggest that self-protection functions could be the expression of a common defensive mechanism shared by social and action spaces.

The Interrelation Between Peripersonal Action Space and Interpersonal Social Space: Psychophysiological Evidence and Clinical Implications

The peripersonal space is an adaptive and flexible interface between the body and the environment that fulfills a dual-motor function: preparing the body for voluntary object-oriented actions to interact with incentive stimuli and preparing the body for defensive responses when facing potentially harmful stimuli. In this position article, we provide arguments for the sensorimotor rooting of the peripersonal space representation and highlight the variables that contribute to its flexible and adaptive characteristics. We also demonstrate that peripersonal space represents a mediation zone between the body and the environment contributing to not only the control of goal-directed actions but also the organization of social life. The whole of the data presented and discussed led us to the proposal of a new theoretical framework linking the peripersonal action space and the interpersonal social space and we highlight how this theoretical framework can account for social behaviors in populations with socio-emotional deficits.

Motor Inhibition to Dangerous Objects: Electrophysiological Evidence for Task-dependent Aversive Affordances

Previous work suggests that perception of an object automatically facilitates actions related to object grasping and manipulation. Recently, the notion of automaticity has been challenged by behavioral studies suggesting that dangerous objects elicit aversive affordances that interfere with encoding of an object's motor properties; however, related EEG studies have provided little support for these claims. We sought EEG evidence that would support the operation of an inhibitory mechanism that interferes with the motor encoding of dangerous objects, and we investigated whether such mechanism would be modulated by the perceived distance of an object and the goal of a given task. EEGs were recorded by 24 participants who passively perceived dangerous and neutral objects in their peripersonal, boundary, or extrapersonal space and performed either a reachability judgment task or a categorization task. Our results showed that greater attention, reflected in the visual P1 potential, was drawn by dangerous and reachable objects. Crucially, a frontal N2 potential, associated with motor inhibition, was larger for dangerous objects only when participants performed a reachability judgment task. Furthermore, a larger parietal P3b potential for dangerous objects indicated the greater difficulty in linking a dangerous object to the appropriate response, especially when it was located in the participants' extrapersonal space. Taken together, our results show that perception of dangerous objects elicits aversive affordances in a task-dependent way and provides evidence for the operation of a neural mechanism that does not code affordances of dangerous objects automatically, but rather on the basis of contextual information.

Close facial emotions enhance physiological responses and facilitate perceptual discrimination

Accumulating evidence indicates that the peripersonal space (PPS) constitutes a privileged area for efficient processing of proximal stimuli, allowing to flexibly adapt our behavior both to the physical and social environment. Whether and how behavioral and physiological signatures of PPS relate to each other in emotional contexts remains, though, elusive. Here, we addressed this question by having participants to discriminate male from female faces depicting different emotions (happiness, anger or neutral) and presented at different distances (50 cm-300 cm) while we measured the reaction time and accuracy of their responses, as well as pupillary diameter, heart rate and heart rate variability. Results showed facilitation of participants' performances (i.e., faster response time) when faces were presented close compared to far from the participants, even when controlling for retinal size across distances. These behavioral effects were accompanied by significant modulation of participants' physiological indexes when faces were presented in PPS. Interestingly, both PPS representation and physiological signals were affected by features of the seen faces such as the emotional valence, its sex and the participants' sex, revealing the profound impact of social context onto the autonomic state and behavior within PPS. Together, these findings suggest that both external and internal signals contribute in shaping PPS representation.

Peripersonal space in social context is modulated by action reward, but differently in males and females

The peripersonal space (PPS) is a multisensory representation of the near-body region of space where objects appear at hand. It also represents a buffer zone protecting the body from external threats and as such it contributes to the organization of social interactions. However, how the combination of embodied objects processing and constraints inherent to social interactions contributes to PPS representation remains an open issue. By using a cooperative task where two male (N = 22) or female (N = 18) participants, sharing the same action space, were requested to select a number of stimuli on a touch-screen table, we investigated the effect of non-uniform distribution of reward-yielding stimuli on selection strategy and perceptual judgments of reachability, used as a proxy of PPS representation. The probability to select a reward-yielding stimulus (50% of the stimuli) was 75% in the proximal space of one of the two confederates. Results showed that participants initially prioritized stimuli in their proximal space and were progressively influenced by the spatial distribution of reward-yielding stimuli, thus invading their confederate's action space when associated with higher probability of reward. The distribution of reward-yielding stimuli led to an increase of reachability threshold, but only when biased towards the participants' distal space. Although the invasion of others' PPS was more pronounced in male participants, the biased distribution of reward-yielding stimuli altered the reachability threshold similarly in males and females. As a whole, the data revealed that reward expectations in relation to motor actions influence both PPS exploration and representation in social context, but differently in males and females.

Can I put myself in your shoes? Sharing peripersonal space reveals the simulation of the action possibilities of others

The representation of the reachable space near the body or peripersonal space (PPS) plays an important role in action with objects and interaction with other people. Here we explored whether the representation of other people's PPS involves a simulation of their action possibility depending on the distance between the observer's body and the other person. We hypothesized that a simulation of action possibilities of others should be activated when they share the PPS of observers. In two experiments using Immersive Virtual Reality, the avatars were shown with their arms free or blocked (motor interference) at a reachable (i.e., Near/shared PPS) or not-reachable (i.e., Far/not-shared PPS) distance by the participants. Participants had to locate a glass in relation to the midline of the avatar's body, i.e., assuming the perspective of the avatar. To directly compare the representation of one's own and others' PPS, in Experiment 1 participants had to locate the glass in relation to themselves with their arms free or blocked. The glass was always within the PPS of either participants or avatars. The results showed that the localization of the glass from the avatar's perspective was slower with the blocked than free arm only when the avatar was in the near shared PPS, similar to the localization from one's own first-person perspective. Instead, there was no effect of motor interference in the far, not-shared PPS. This suggests that the representation of other people's PPS can involve motor simulation mechanisms when we share a common peripersonal area.

Opposing force fields induce direction-specific sensorimotor adaptation but a non-specific perceptual shift consistent with a contraction of peripersonal space representation

Most of our daily interactions with objects occur in the space immediately surrounding the body, i.e. the peripersonal space. The peripersonal space is characterized by multisensory processing of objects which are coded in terms of potential actions, specifying for instance whether objects are within reach or not. Our recent work suggested a link between exposure to a new force field, which changed the effector dynamics, and the representation of peripersonal space. To better understand the interplay between the plasticity of the motor system and peripersonal space representation, the present study examined whether changing the direction of the force field specifically modified the perception of action boundaries. Participants seated at the centre of an experimental platform estimated visual targets' reachability before and after adapting upper-limb reaching movements to the Coriolis force generated by either clockwise or counter clockwise rotation of the platform (120°/s). Opposite spatial after-effects were observed, showing that force-field adaptation depends on the direction of the rotation. In contrast, perceived action boundaries shifted leftward following exposure to the new force field, regardless of the direction of the rotation. Overall, these findings support the idea that abrupt exposure to a new force field results in a direction-specific updating of the central sensorimotor representations underlying the control of arm movements. Abrupt exposure to a new force field also results in a nonspecific shift in the perception of action boundaries, which is consistent with a contraction of the peripersonal space. Such effect, which does not appear to be related to state anxiety, could be related to the protective role of the peripersonal space in response to the uncertainty of the sensorimotor system induced by the abrupt modification of the environment.

Peri-Personal Space Tracing by Hand-Blink Reflex Modulation in Patients with Chronic Disorders of Consciousness

The assessment of awareness in patients with chronic Disorders of Consciousness (DoC), including Unresponsive Wakefulness Syndrome (UWS) and Minimally Conscious State (MCS), is challenging. The level of awareness impairment may depend on the degree of deterioration of the large-scale cortical-thalamo-cortical networks induced by brain injury. Electrophysiological approaches may shed light on awareness presence in patients with DoC by estimating cortical functions related to the cortical-thalamo-cortical networks including, for example, the cortico-subcortical processes generating motor responses to the perturbation of the peri-personal space (PPS). We measured the amplitude, latency, and duration of the hand-blink reflex (HBR) responses by recording electromyography (EMG) signals from both the orbicularis oculi muscles while electrically stimulating the median nerve at the wrist. Such a BR is thought to be mediated by a neural circuit at the brainstem level. Despite its defensive-response nature, HBR can be modulated by the distance between the stimulated hand and the face. This suggests a functional top-down control of HBR as reflected by HBR features changes (latency, amplitude, and magnitude). We therefore estimated HBR responses in a sample of patients with DoC (8 MCS and 12 UWS, compared to 15 healthy controls -HC) while performing a motor task targeting the PPS. This consisted of passive movements in which the hand of the subject was positioned at different distances from the participant's face. We aimed at demonstrating a residual top-down modulation of HBR properties, which could be useful to differentiate patients with DoC and, potentially, demonstrate awareness preservation. We found a decrease in latency, and an increase in duration and magnitude of HBR responses, which were all inversely related to the hand-to-face distance in HC and patients with MCS, but not in individuals with UWS. Our data suggest that only patients with MCS have preserved, residual, top-down modulation of the processes related to the PPS from higher-order cortical areas to sensory-motor integration network. Although the sample size was relatively small, being thus our data preliminary, HBR assessment seems a rapid, easy, and first-level tool to differentiate patients with MCS from those with UWS. We may also hypothesize that such a HBR modulation suggests awareness preservation.

Positive self-perception and corticospinal excitability: Recalling positive behavior expands peripersonal space boundaries

Converging evidence suggests that peripersonal space has dynamic properties, that can be influenced by motor and cognitive factors. Here, we investigated whether changes in self-perception may impact upon peripersonal representation. Specifically, employing non-invasive brain stimulation, we tested whether corticospinal excitability elicited by objects placed in the vertical peripersonal vs extrapersonal space can be influenced by changes in self-perception after recalling a personal experience inducing the feeling of high power (vs. positivity vs. low power). In a preliminary study (Study 1, N = 39) participants were presented with an object, whose position was manipulated in the horizontal vs vertical space. We assessed corticospinal excitability by measuring Motor Evoked Potentials (MEPs) using Transcranial Magnetic Stimulation with Electromyography co-registration (TMS-EMG). In the horizontal condition, we replicated the well-known motor facilitation induced by objects falling in the peri vs extrapersonal space, while in the vertical dimension MEPs were higher in the extrapersonal space. In the main experiment (Study 2), participants (N = 55) were randomly assigned to feel high power, low power, or a general positive emotion and were asked to observe the same object positioned either in the peripersonal or in the extrapersonal vertical space. Results showed that in the low power condition MEPs were higher in the extrapersonal vs peripersonal, as in Study 1, while in high power and positive conditions MEPs were not influenced by distance. Taken together, our findings suggest a dissociable pattern of motor facilitation underlying vertical vs horizontal space perception and, crucially, that changes in self-perception can influence such a representation.

Toward understanding the neurophysiological basis of peripersonal space: An EEG study on healthy individuals

The subcortical mechanisms subtending the sensorimotor processes related to the peripersonal space (PPS) have been well characterized, whereas less evidence is available concerning the cortical mechanisms. We investigated the theta, alpha and beta event-related spectral perturbations (ERSP) while holding the forearm in different positions into the PPS of the face. Fifty healthy individuals were subjected to EEG recording while being provided with median nerve electric stimulation at the wrist of the right hand held at different hand-to-face distances. Theta and beta rhythms were significantly perturbed depending on the hand-to-face distance, whereas alpha oscillations reflected a more general, non-specific oscillatory response to the motor task. The perturbation of theta and beta frequency bands may reflect the processes of top-down modulation overseeing the conscious spatiotemporal encoding of sensory-motor information within the PPS. In other words, such perturbation reflects the continuous update of the conscious internal representations of the PPS to build up a purposeful and reflexive motor response.

Reinforcement Emotion-Cognition System: A Teaching Words Task

The goal of this paper is to suggest a system for intelligent learning environments with robots modeling of emotion regulation and cognition based on quantitative motivation. A detailed interactive situation for teaching words is proposed. In this study, we introduce one bottom-up collaboration method for emotion-cognition interplay and behaviour decision-making. Integration with gross emotion regulation theory lets the proposed system adapt to natural interactions between students and the robot in emotional interaction. Four key ideas are advocated, and they jointly set up a reinforcement emotion-cognition system (RECS). First, the quantitative motivation is grounded on external interactive sensory detection, which is affected by memory and preference. Second, the emotion generation triggered by an initial motivation such as external stimulus is also influenced by the state in the previous time. Third, the competitive and cooperative relationship between emotion and motivation intervenes to make the decision of emotional expression and teaching actions. Finally, cognitive reappraisal, the emotion regulation strategy, is introduced for the establishment of emotion transition combined with personalized cognition. We display that this RECS increases the robot emotional interactive performance and makes corresponding teaching decision through behavioural and statistical analysis.

Sensori-motor adaptation to novel limb dynamics influences the representation of peripersonal space

Peripersonal space can be considered as the interface between the body and the environment, where objects can be reached and which may serve as a reference for the central nervous system with regard to possible actions. Peripersonal space can be studied by assessing the perception of the reachable space, which depends on the body's physical characteristics (i.e., arm length) since their modifications have been shown to be associated with a change in peripersonal space representation. However, it remains unclear whether the representation of limb dynamics also influences the representation of peripersonal space. The present study investigated this issue by perturbing the force-field environment. A novel force field was created by rotating an experimental platform where participants were seated while they reached towards visual targets. Manual reaching performance was assessed before, during and after platform rotation. Crucially, perception of peripersonal space was also assessed, with reachability judgments, before and after platform rotation. As expected, sensori-motor adaptation to the perturbed force field was observed. Our principal finding is that peripersonal space was systematically perceived as closer to the body after force-field adaptation. Two control experiments showed no significant difference in reachability judgments when no reaching movements were performed during platform rotation or when reaching movements were performed without platform rotation, suggesting that the change in perceived peripersonal space resulted from exposure to new limb dynamics. Overall, our findings show that sensori-motor adaptation of reaching movements to a new force field, which does not directly influence arm length but results in the updating of the arm's internal model of limb dynamics, interacts with the perceptual categorisation of space, supporting a motor contribution to the representation of peripersonal space.

This shoe, that tiger: Semantic properties reflecting manual affordances of the referent modulate demonstrative use

Demonstrative reference is central to human communication. But what influences our choice of demonstrative forms such as “this” and “that” in discourse? Previous literature has mapped the use of such “proximal” and “distal” demonstratives onto spatial properties of referents, such as their distance from the speaker. We investigated whether object semantics, and specifically functional properties of referents, also influence speakers’ choices of either demonstrative form. Over two experiments, we presented English, Danish and Italian speakers with words denoting animate and inanimate objects, differing in size and harmfulness, and asked them to match them with a proximal or a distal demonstrative. Objects that offer more affordances for manipulation (smaller and harmless) elicited significantly more proximal demonstratives. These effects were stronger for inanimate referents, in line with the predictions of sensory-functional views on object semantics. These results suggest that demonstrative use may be partly grounded on manual affordances, and hints at the possibility of using demonstratives as a proxy to investigate the organization of semantic knowledge.

Investigating Neural Sensorimotor Mechanisms Underlying Flight Expertise in Pilots: Preliminary Data From an EEG Study

Over the last decade, the efforts toward unraveling the complex interplay between the brain, body, and environment have set a promising line of research that utilizes neuroscience to study human performance in natural work contexts such as aviation. Thus, a relatively new discipline called neuroergonomics is holding the promise of studying the neural mechanisms underlying human performance in pursuit of both theoretical and practical insights. In this work, we utilized a neuroergonomic approach by combining insights from ecological psychology and embodied cognition to study flight expertise. Specifically, we focused on the Mirror Neuron system as a key correlate for understanding the interaction between an individual and the environment, suggesting that it can be used to index changes in the coupling of perception-action associated with skill development. In this study, we measured the EEG mu suppression as a proxy of the Mirror Neuron system in experts (pilots) and novices while performing a distance estimation task in a landing scenario. To survey the specificity of this measure, we considered central, parietal and occipital electrode pools and analyzed alpha (8–13 Hz) and beta (18–25 Hz) rhythm bands. We hypothesized that in experts vs. novices, specific neural sensorimotor brain activity would underpin the connection between perception and action in an in-flight context. Preliminary results indicate that alpha and beta rhythm suppression was area-specific irrespective of groups, present in the central electrodes placed over the motor areas. Group analysis revealed that specifically alpha mu rhythm, but not beta, was significantly more suppressed in pilots vs. novices. Complementing these findings we found a trend in which the strength of mu suppression increased with the sense of presence experienced by the pilots. Such sensorimotor activation is in line with the idea that for a pilot, a distance judgment is intimately associated with the function of landing. This reflects the ability to use optical invariants to see the world in terms of the capabilities of the aircraft (e.g., reachability and glide angle). These preliminary findings support the role of embodied simulation mechanisms in visual perception and add important insights into a practical understanding of flight expertise, suggesting sensorimotor mechanisms as potential neuro-markers.

A sequential trial effect based on the motor interference effect from dangerous objects: An ERP study

INTRODUCTION

This study aims to investigate whether processing a prepared response toward a dangerous object in a previous trial influences subsequent trial processing.

METHODS

The design manipulated the Go/NoGo factor of the current trial, the target dangerousness of the previous trial and that of the current trial.

RESULTS

In current Go trials, the behavioral results revealed a classical motor interference effect in trials that were preceded by a safe trial (a longer reaction time (RT) and a larger error rate for the previous safe and current dangerous (sD) condition than for the previous safe and current safe (sS) condition). However, the motor interference effect diminished in trials that were preceded by a dangerous trial (insignificant differences in the mean RTs and error rates between the previous dangerous and current dangerous (dD) condition and the previous dangerous and current safe (dS) condition). The event-related potential (ERP) results identified more positive P2 and parietal P3 amplitudes (indicating attentional resource allocation) for the dD condition than for the dS condition. However, the P2 and parietal P3 amplitudes of the sD condition did not significantly differ from those of the sS condition.

DISCUSSIONS

These results support the hypothesis that the avoidance motivation elicited by a dangerous target in a previous trial may indicate a dangerous situation, which leads to recruitment of more attentional resources allocated to the subsequent dangerous trial. Therefore, RTs are improved and errors are reduced in the consecutive dangerous condition, subsequently decreasing the motor interference effect in trials preceded by a dangerous trial compared with trials preceded by a safe trial. However, analysis of current NoGo trials revealed that none of the main effects or interactions reached significance in both the behavioral and ERP results, indicating that the hypothesis holds true only if the prepared response needs to be executed.

The influence of threat on perceived spatial distance to out-group members

A classic example of discriminatory behavior is keeping spatial distance from an out-group member. To explain this social behavior, the literature offers two alternative theoretical options that we label as the "threat hypothesis" and the "shared-experience hypothesis". The former relies on studies showing that out-group members create a sense of alertness. Consequently, potentially threatening out-group members are represented as spatially close allowing the prevention of costly errors. The latter hypothesis suggests that the observation of out-group members reduces the sharing of somatosensory experiences and, thus, increases the perceived physical distance between oneself and others. In the present paper, we pitted the two hypotheses against each other. In Experiment 1, Caucasian participants expressed multiple implicit "Near/Far" spatial categorization judgments from a Black-African Avatar and a White-Caucasian Avatar located in a 3D environment. Results indicate that the Black-African Avatar was categorized as closer to oneself, as compared with the White-Caucasian Avatar, providing support for "the threat hypothesis". In Experiment 2, we tested to which degree perceived threat contributes to this categorization bias by manipulating the avatar's perceived threat orthogonally to group membership. The results indicate that irrespective of group membership, threatening avatars were categorized as being closer to oneself as compared with no threatening avatars. This suggests that provided information about a person and not the mere group membership influences perceived distance to the person.

Frontier of Self and Impact Prediction

The construction of a coherent representation of our body and the mapping of the space immediately surrounding it are of the highest ecological importance. This space has at least three specificities: it is a space where actions are planned in order to interact with our environment; it is a space that contributes to the experience of self and self-boundaries, through tactile processing and multisensory interactions; last, it is a space that contributes to the experience of body integrity against external events. In the last decades, numerous studies have been interested in peripersonal space (PPS), defined as the space directly surrounding us and which we can interact with (for reviews, see Cléry et al., 2015b; de Vignemont and Iannetti, 2015; di Pellegrino and Làdavas, 2015). These studies have contributed to the understanding of how this space is constructed, encoded and modulated. The majority of these studies focused on subparts of PPS (the hand, the face or the trunk) and very few of them investigated the interaction between PPS subparts. In the present review, we summarize the latest advances in this research and we discuss the new perspectives that are set forth for futures investigations on this topic. We describe the most recent methods used to estimate PPS boundaries by the means of dynamic stimuli. We then highlight how impact prediction and approaching stimuli modulate this space by social, emotional and action-related components involving principally a parieto-frontal network. In a next step, we review evidence that there is not a unique representation of PPS but at least three sub-sections (hand, face and trunk PPS). Last, we discuss how these subspaces interact, and we question whether and how bodily self-consciousness (BSC) is functionally and behaviorally linked to PPS.

Idiosyncratic representation of peripersonal space depends on the success of one's own motor actions, but also the successful actions of others!

Peripersonal space is a multisensory representation of the environment around the body in relation to the motor system, underlying the interactions with the physical and social world. Although changing body properties and social context have been shown to alter the functional processing of space, little is known about how changing the value of objects influences the representation of peripersonal space. In two experiments, we tested the effect of modifying the spatial distribution of reward-yielding targets on manual reaching actions and peripersonal space representation. Before and after performing a target-selection task consisting of manually selecting a set of targets on a touch-screen table, participants performed a two-alternative forced-choice reachability-judgment task. In the target-selection task, half of the targets were associated with a reward (change of colour from grey to green, providing 1 point), the other half being associated with no reward (change of colour from grey to red, providing no point). In Experiment 1, the target-selection task was performed individually with the aim of maximizing the point count, and the distribution of the reward-yielding targets was either 50%, 25% or 75% in the proximal and distal spaces. In Experiment 2, the target-selection task was performed in a social context involving cooperation between two participants to maximize the point count, and the distribution of the reward-yielding targets was 50% in the proximal and distal spaces. Results showed that changing the distribution of the reward-yielding targets or introducing the social context modified concurrently the amplitude of self-generated manual reaching actions and the representation of peripersonal space. Moreover, a decrease of the amplitude of manual reaching actions caused a reduction of peripersonal space when resulting from the distribution of reward-yielding targets, while this effect was not observed in a social interaction context. In that case, the decreased amplitude of manual reaching actions was accompanied by an increase of peripersonal space representation, which was not due to the mere presence of a confederate (control experiment). We conclude that reward-dependent modulation of objects values in the environment modifies the representation of peripersonal space, when resulting from either self-generated motor actions or observation of motor actions performed by a confederate.

Physiological Response to Facial Expressions in Peripersonal Space Determines Interpersonal Distance in a Social Interaction Context

Accurate control of interpersonal distances in social contexts is an important determinant of effective social interactions. Although comfortable interpersonal distance seems to be dependent on social factors such as the gender, age and activity of the confederates, it also seems to be modulated by the way we represent our peripersonal-action space. To test this hypothesis, the present study investigated the relation between the emotional responses registered through electrodermal activity (EDA) triggered by human-like point-light displays (PLDs) carrying different facial expressions (neutral, angry, happy) when located in the participants peripersonal or extrapersonal space, and the comfort distance with the same PLDs when approaching and crossing the participants fronto-parallel axis on the right or left side. The results show an increase of the phasic EDA for PLDs with angry facial expressions located in the peripersonal space (reachability judgment task), in comparison to the same PLDs located in the extrapersonal space, which was not observed for PLDs with neutral or happy facial expressions. The results also show an increase of the comfort distance for PLDs approaching the participants with an angry facial expression (interpersonal comfort distance judgment task), in comparison to PLDs with happy and neutral ones, which was related to the increase of the physiological response. Overall, the findings indicate that comfort social space can be predicted from the emotional reaction triggered by a confederate when located within the observer’s peripersonal space. This suggests that peripersonal-action space and interpersonal-social space are similarly sensitive to the emotional valence of the confederate, which could reflect a common adaptive mechanism in specifying theses spaces to subtend interactions with both the physical and social environment, but also to ensure body protection from potential threats.

The effect of height and shoulder-to-hip ratio on interpersonal space in virtual environment

Previous research has associated men's physical features such as height and Shoulder-to-Hip Ratio (SHR) with dominance. Proxemics literature has suggested that the interpersonal space (comfort distance) increases in threatening and uncomfortable situations and decreases in unthreatening and comfortable situations. In the current study, we aimed to investigate the effect of different heights and SHRs on comfortable interpersonal distance by systematic manipulation of virtual confederates bodily features. More specifically, participants determined their comfort distances from virtual male confederates with different heights and SHRs in a virtual environment. We hypothesized that a virtual confederate's height and SHR influences the perception of interpersonal dominance; and consequently interpersonal space increases for taller and broader confederates as a result of increased interpersonal dominance. Results showed that comfortable interpersonal distance was positively associated with height for male participants, but not for female participants. No effect was found for shoulder width, neither for male nor female participants. Results were discussed in terms of the importance of height as a signal of dominance and fighting ability.

Emotional metacontrol of attention: Top-down modulation of sensorimotor processes in a robotic visual search task

Emotions play a significant role in internal regulatory processes. In this paper, we advocate four key ideas. First, novelty detection can be grounded in the sensorimotor experience and allow higher order appraisal. Second, cognitive processes, such as those involved in self-assessment, influence emotional states by eliciting affects like boredom and frustration. Third, emotional processes such as those triggered by self-assessment influence attentional processes. Last, close emotion-cognition interactions implement an efficient feedback loop for the purpose of top-down behavior regulation. The latter is what we call ‘Emotional Metacontrol’. We introduce a model based on artificial neural networks. This architecture is used to control a robotic system in a visual search task. The emotional metacontrol intervenes to bias the robot visual attention during active object recognition. Through a behavioral and statistical analysis, we show that this mechanism increases the robot performance and fosters the exploratory behavior to avoid deadlocks.

Manipulating time and space: Collision prediction in peripersonal and extrapersonal space

Being able to predict potential collisions is a necessary survival prerequisite for all moving species. Temporal and spatial information is fundamental for this purpose. However, it is not clear yet if the peripersonal (i.e. near) and extrapersonal (i.e. far) distance between our body and the moving objects affects the way in which we can predict possible collisions. In order to assess this, we manipulated independently velocity and path of two balls moving one towards the other in such a way as to collide or not in peripersonal and extrapersonal space. In two experiments, participants had to judge if these balls were to collide or not. The results consistently showed a lower discrimination capacity and a more liberal tendency to predict collisions when the moving balls were in peripersonal space and their velocity was different rather than equal. This did not happen in extrapersonal space. Therefore, peripersonal space was particularly affected by temporal information. The possible link between the motor and anticipatory adaptive function of peripersonal space and collision prediction mechanisms is discussed.

Response inhibition or evaluation of danger? An event-related potential study regarding the origin of the motor interference effect from dangerous objects

Previous studies have identified an interference effect from dangerous objects on prepared responses. However, its origin remains arguable. This study investigated the neural processes of this motor interference effect. The design adopted a motor priming paradigm mixed with a Go/NoGo task. Pictures of a left or right hand were used as primes, and green (Go signal) or red (NoGo signal) circles superimposed on dangerous or safe objects were used as targets. Participants were instructed to prepare the corresponding key press using the hand that was consistent with the handedness of the prime and not to execute until a Go signal appeared. Behavioral results indicated longer reaction times and a trend that participants made more errors for the dangerous condition than for the safe condition in the Go trials. However, the difference between the error rates for the dangerous and safe conditions did not emerge in the NoGo trials. Event-related potential analysis revealed a similar effect on the P3 component, which may reflect an assignment of cognitive resources to evaluate danger. More positive parietal P3 amplitudes were identified in response to the dangerous condition in the Go trials. However, the difference in the P3 amplitudes between the dangerous and safe conditions was not significant in the NoGo trials. Together, the motor interference effect from dangerous objects may originate from the danger evaluations. Furthermore, differences between the dangerous and safe conditions also emerged in the P1, posterior N1, P2, and posterior N2 components; the possible processes that underlie these components were discussed.

Slower attentional disengagement but faster perceptual processing near the hand

Many recent studies have reported altered visual processing near the hands. However, there is no definitive agreement about the mechanisms responsible for this effect. One viewpoint is that the effect is predominantly attentional while others argue for the role of pre-attentive perceptual differences in the manifestation of the hand-proximity effect. However, in most of the studies pre-attentional and attentional effects have been conflated. We argue that it is important to dissociate the effect of hand proximity on perception and attention to better theorize and understand how visual processing is altered near the hands. We report two experiments using a visual search task where participants completed a visual search task with their hands either on the monitor or on their lap. When on the monitor, the target could appear near the hand or farther away. In experiment 1, a letter search task showed steeper search slope near the hand suggesting slower attentional disengagement. However, the intercept was smaller in the near hand condition suggesting faster perceptual processing. These results were also replicated in experiment 2 with a conjunction search task with target present and absent conditions and 4 set sizes. The results suggest that there are dissociable effects of hand proximity on perception and attention. Importantly, the pre-attentive advantage of hand proximity does not translate to attentional benefit, but a processing cost. The results of experiment 2 additionally indicate that the steeper slope does not arise from any spatial biases in how search proceeds, but an indicator of slower attentional processing near the hands. The results also suggest that the effect of hand proximity on attention is not spatially graded whereas its effect on perceptuo-motor processes seems to be.

The Automaticity of Affordance of Dangerous Object

Objects observation automatically elicits the activation of a reach-to-grasp response specifically directed to interact with the object, which is termed affordance. Murphy, van Velzen, and de Fockert (2012) found that only when an irrelevant object receives sufficient attention, it can potentiate an action. However, it remains unclear whether the dangerous object would afford an action when it receives insufficient attention. In this study, we manipulated the perceptual load in a letter identification task. Participants were required to identify a target letter with the right or left hand while ignoring a neutral or dangerous graspable object. The target letter was presented either on its own (low perceptual load), alongside five non-target letters (high load), or alongside eight non-target letters (super high load). Under the low perceptual load, for both neutral and dangerous object, responses were faster when the action afforded by the ignored object was congruent (vs. incongruent) with the current target response (t(27) = 4.44, p < .001; t(27) = 7.99, p < .001, respectively). However, during the high perceptual load, for dangerous object, responses were slower when the action afforded by the ignored object was congruent (vs. incongruent) with the current target response (t(27) = 4.97, p < .001). There was not any effect for both neutral object and dangerous object under super high perceptual load. These results suggest the affordance of dangerous object is also sensitive to the perceptual load. An irrelevant dangerous object can’t potentiate an action if it receives insufficient attention.

Social Threat and Motor Resonance: When a Menacing Outgroup Delays Motor Response

Motor resonance (MR) involves the activation of matching motor representations while observing others' actions. Recent research has shown that such a phenomenon is likely to be influenced by higher order variables such as social factors (e.g., ethnic group membership). The present study investigates whether and how the perception of a social threat elicited by an outgroup member and by contextual cues can modulate motor responses while an individual observes others' movements. In an experimental study based on an action observation paradigm, we asked participants to provide answers through computer mouse movements (MouseTracker). We manipulated the agents' group membership (ingroup vs. outgroup) and the social valence of the objects present in a context (neutral vs. threatening) to elicit social menace through contextual cues. Response times and computer mouse trajectories were recorded. The results show a higher level of MR (i.e., participants started to respond earlier and were faster at responding) when observing an action performed by the ingroup members rather than by the outgroup members only when threatening objects are present in a given context. Participants seem to resonate better with their ingroup; conversely, the outgroup member movements tend to delay motor responses. Therefore, we extend prior research going beyond the general ingroup bias effect on MR and showing that the interaction between membership and contextual cues is likely to elicit threat-related stereotypes. Practical implications of these findings are discussed.

Keeping you at arm's length: modifying peripersonal space influences interpersonal distance

Peripersonal space represents the area around the body where objects are coded in motor terms for the purpose of voluntary goal-directed actions. Previous studies have suggested that peripersonal space is also a safe space linked with our private area, influencing interpersonal space in social contexts. However, whether these two spaces rely on similar embodied processes remains an open issue. In the present study, participants observed a point-light walker (PLW) approaching them from different directions and passing near them at different distances from their right or left shoulder. While approaching, the PLW disappeared at a distance of 2 m and the task for the participants was to estimate if the interpersonal distance, at the time the PLW would have reached their level, was comfortable or not. Between two sessions of comfort judgments, the participants manipulated a 70 cm tool entailing an extension of peripersonal space, or a 10 cm tool entailing no extension of peripersonal space. The results revealed that the comfortable interpersonal distance was larger when the PLW crossed the mid-sagittal plane of the participants than when it approached them laterally, with a concomitant increase of response time. After participants manipulated the long tool, comfortable interpersonal distance increased, but predominantly when the PLW trajectory implied crossing the participants' mid-sagittal plane. This effect was not observed when participants manipulated the short tool. Two control tasks showed that using the long tool modified the reachability (control 1), but not the time to passage (control 2) estimates of PLW stimuli, suggesting that tool use extended peripersonal space without changing perceived visual distances. Overall, the data show that comfortable interpersonal distance is linked to the representation of peripersonal space. As a consequence, increasing peripersonal space through tool use has the immediate consequence that comfortable interpersonal distance from another person also increases, suggesting that interpersonal-comfort space and peripersonal-reaching space share a common motor nature.

Approaching threat modulates visuotactile interactions in peripersonal space

The region surrounding our body (i.e. peripersonal space) is coded in a multimodal representation by fronto-parietal bimodal neurons integrating tactile stimuli on the body with nearby visual stimuli. This has often been suggested to serve a defensive purpose, which we propose could be mediated through visuotactile predictions. An approaching threat would then be of particular interest to peripersonal space processing. To investigate this, we asked participants to respond as fast as possible to a tactile stimulus on the hand, while looking at an animation of an approaching or receding spider or butterfly. Tactile stimulation was applied at one of 25 possible time points during the animation. Tactile reaction times were faster when an approaching stimulus was closer to the hand at the time of tactile presentation. Critically, this effect of distance on reaction times was larger when participants saw an approaching spider compared to an approaching butterfly, but only for participants who were afraid of spiders. This finding demonstrates that the perceived threat of an approaching stimulus modulates visuotactile interactions in peripersonal space and is consistent with the idea that visuotactile predictions are important for defensive purposes and maintaining bodily integrity.