When we pause and relax, strange sensations might arise; a tingling in the hand, an itch on the foot, often without any clear cause. These "ghost" bodily experiences, known as spontaneous sensations (SPS), offer a unique window into how we perceive our bodies. In an online experimental study of 175 participants, we examined how SPS differ across body regions (hands, feet, whole body) and whether individual differences in visual attention shape these experiences. We measured both the general tendency to notice SPS (SPSTrait) and in-the-moment awareness of them (SPSState), alongside performance on a visual Posner task of endogenous attention. SPSTrait was reported more strongly in the whole body compared to the feet, suggesting a broad, higher-order body representation. In contrast, SPSState did not vary by body part. These experiences, whether momentary that is, SPSState, or habitual that is, SPSTrait, were unrelated to how participants performed on the visual attention task. Our findings support a representational distinction: SPSTrait may reflect somatorepresentation, a top-down, global body model, whereas SPSState may arise from bottom-up somatosensation.

Perceptual illusions of having extra body parts offer an experimental method to investigate the limits of body perception. It is well established that the illusory perception of an artificial hand as one's own is dependent on spatial congruency. That is, the seen hand needs to be in a posture congruent with the actual hand. In this study, we aimed to investigate how constrained the representation of a supernumerary body part is by systematically varying the perceived rotation of an illusory sixth finger. Surprisingly, participants felt a sixth finger on their hand consistently for all induced orientations of finger extension and abduction (0°, 90°, 135°, 180°). The illusion showed no apparent decrease with increased induced rotation of the extra finger. We also measured the perceived orientation of the sixth finger, and our results show that participants felt an extended and an abducted sixth finger increasingly more rotated as the induced rotation also increased, while feeling their actual little finger in a normal position. Our results indicate that one can feel a supernumerary finger in an incongruent spatial location from one's actual fingers and hand, to an extent of 180° of extension (finger up) and 180° of abduction (finger to the side). We therefore propose that the representation of the supernumerary finger has a strong independence from the actual finger and hand-frame reference.

People with anorexia nervosa (AN) exhibit altered responses to embodiment and motor imagery tasks, indicating a more malleable mental representation of their body compared to healthy controls (HC). While this has been observed with the actual body, little is known about the mental representation of supernumerary body parts. Recently, it was demonstrated in HC that illusions of supernumerary fingers are not constrained by posture congruency. The current study aimed to evaluate the differences in the malleability of body representation for supernumerary body parts comparing 30 participants with AN and 30 HC using the sixth finger illusion which is a body illusion based on conflicting visual and tactile signals that lead to create the illusory perception of having an extra finger (i.e. a sixth finger). Synchronous visual-tactile stroking was delivered at four abduction orientations: 0°, 90°, 135° and 180°, plus a control condition. Participants were asked to complete an ownership questionnaire to judge the little finger's perceived orientation and the sixth finger's felt orientation when they agreed to feel six fingers. Both groups experienced the sixth finger in all orientations, despite biomechanical constraints. However, AN participants perceived the sixth finger closer to the hand's position. Previous studies in AN report higher flexibility of some body representation domains, such as embodiment and motor imagery. Interestingly, our study highlights that this higher flexibility does not seem to apply to all domains of the representation of the bodily self: AN participants showed reduced flexibility for the perceived orientation of the extra finger.

Mental representations guide action planning and body execution. While hand representations have been extensively studied, not much is known about differences between hands, feet and whole-body representations. Previous studies tell us about functional and sensory differences between body parts and between parts and whole body, however hands and feet studies also tell us that it matters if we are aware of using motor strategies when we activate body representations, and this has not been compared yet between body parts and between parts and whole body. Sixty participants (M = 26.68, SD = 8.22) took part in an online experiment, including Implicit Association Tests (IAT) where participants are not fully aware of using a motor strategy, and a Mental Motor Chronometry (MMC), a more explicit task requiring awareness of imagining actions. The influence of visual imagery was controlled by administering a Vividness of Visual Imagery (VVI) questionnaire to exclude non-motor-related effects. Results show that when the task requires less awareness to be solved, there are no differences between hands, feet, and whole body. Differences are found when more awareness of body representation and related processes is required, with a more pronounced and finer representation of hands than the whole body. No differences between hands versus feet and whole body versus feet were found. These results highlight the importance of awareness in the representation of body parts and suggest that motor strategies contribute to the differentiation between hand and whole-body representations, a distinction not accounted for by visual imagery differences.

IMPORTANT: THE REVISED VERSION OF THIS PREPRINT IS NOW PUBLISHED IN THE QUARTERLY JOURNAL OF EXPERIMENTAL PSYCHOLOGY , SEE HERE: https://doi.org/10.1177/17470218251324932When moving our physical body, we use our mental body representation to guide action planning and execution. Not much is known about the differences in these representations across body districts. We compared implicit and more explicit motor imagery for hands, feet and whole-body representations. Sixty participants (age M = 26.68, SD = 8.22), took part in an online experiment including Implicit Association Tests (IAT; Greenwald et al., 1998), as a more implicit task, and a Mental Motor Chronometry (MMC), as a more explicit task (Brusa et al., 2021). The influence of visual imagery was controlled by administering a Vividness of Visual Imagery (VVI) questionnaire. The results show that when the task requires less awareness to be solved, in other words, it is more implicit, there are no differences between hands, feet and whole body. While differences can be found when more awareness of our own body representation and related processes is required, with a stronger motor imagery for the hands than the whole body. This finding is not due to visual imagery differences, as demonstrated by the results of the visual imagery questionnaire. Our findings suggest that hands were stronger than the whole body in the body in action representations.

To understand conditions such as body dysmorphic disorder, we need to understand healthy individuals’ perceptual, conceptual, and emotional representations of their bodies. Not much is known about the differences in these representations across body districts, for example, hands, feet, and whole-body, despite their differences at sensory and functional levels. To understand this, we developed more implicit and explicit measures of body satisfaction for these body districts. Sixty-seven participants (age M = 30.66, SD = 11.19) completed a series of online Implicit Association Tests (IAT) and a Body Image Satisfaction Visual Analogue Scale (BISVAS; explicit) for each body district (hands/feet/whole body). The results show no differences in the more implicit level of awareness in hands, feet and whole body, while differences are apparent at a more explicit level of awareness, with higher scores for body image satisfaction for the hands than the whole body and marginally significant lower scores for feet than hands. Those findings suggest that visual attention, level of concern attributed to a body district, and disgust drivers are possible factors affecting the experience of attitudinal body image satisfaction.

Disgust is a powerful emotion that evolved to protect us from contamination and diseases; it also cores to very human feelings, such as shame. In anorexia nervosa, most of the knowledge on disgust regards food. However, disgust can be elicited by varied drivers, including body-related self-disgust, which may be more central to this condition. Here, we investigate in depth how disgust triggers related to the body influence altered representations in anorexia nervosa. Women with anorexia nervosa and healthy women performed the Hand Laterality Task, in which they were asked to judge the laterality of hands without and with a disgust charging feature (i.e., with a body product or with a body violation). We computed accuracy and reaction time for the effect of biomechanical constraints, an index of motor imagery. We also measured the general disgust sensitivity through a self-report questionnaire. Participants with anorexia nervosa were overall less accurate and slower compared with controls, suggesting a non-canonical (i.e., not based on motor imagery) approach to solving the task. However, they showed the same pattern of responses as controls for disgust-charged stimuli, despite reporting higher levels of disgust sensitivity. Our results suggested the absence of specific effects of disgust drivers on the (altered) body in action representation in anorexia nervosa. We discuss this evidence focusing on the role of the psychopathological symptoms characterising anorexia nervosa. We also reflect on the efficacy of experimental methodologies used to detect alterations in body representation in this clinical condition.

When we relax, our attention shifts to sensations across our limbs, such as itching or tingling, known as spontaneous sensations (SPS). One hundred and seventy-five individuals took part in an online experiment to explore whether SPS present differently in our hands, feet, and our whole body and whether visual attention ability influences the SPS experience. We designed an online experiment measuring the general tendency to experience SPS (SPSTrait) and the experience of SPS in a precise moment (SPSState) along with an endogenous visual attention Posner task. Our findings show that we tend to experience SPS, in general, more strongly in our whole body than our feet (SPSTrait), while our in-the-moment attention to SPS (SPSState) is the same across the body districts. This experience does not depend on visual attention differences. Those findings support the distinction between a higher-order representational level, somatorepresentation for the SPSTrait experience, aimed for the whole body; and a more generalised lower-order representational level, somatosensation, for the SPSState experience.

The classic rubber hand illusion (RHI), based on visual, proprioceptive, and tactile feedback, can affect actions. However, it is not known whether these effects still occur if the paradigm is administered without visual feedback. In this study, we used the somatic RHI to test in thirty-two healthy individuals whether the incorporation of the rubber hand based on proprioceptive and tactile information only is sufficient to generate changes in actions. We measured maximum grip aperture (GA) changes towards a target and associated brain activations within the dorsal stream before and after the somatic RHI. Behavioural and neuroimaging data do not support an effect on maximum GA when the RHI is based on proprioceptive and tactile information only.

The hand laterality task (HLT) and the foot laterality task (FLT) are used to explore motor imagery, the ability to imagine an action without executing it. With our limbs, we interact with our body, with others, and with the environment. These contacts might cause negative feelings, such as disgust. Disgust is elicited by different drivers. For instance, body products and body envelope violations provoke disgust to avoid contaminations and to avoid damaging our bodies. However, not much is known about how disgust changes our motor imagery processes. In this study, we examined whether there is any difference in the ability to imagine hands and feet when these are emotionally charged with reminders of disgust. Thirty-six participants completed an online version of a classic (neutral) HLT and FLT and two emotionally charged (disgust) versions. Our findings show that when body parts are modified so that they elicit emotional processing, disgust is salient overall, rather than being salient specifically for actions. This is true for both our hands and our feet.

The mental representation of the body in action can be explored using motor imagery (MI) tasks. MI tasks can be allocated along a continuum going from more implicit to more explicit tasks, where the discriminant is the degree of action monitoring required to solve the tasks (which is the awareness of using the mental representation of our own body to monitor our motor imagery). Tasks based on laterality judgments, such as the Hand Laterality Task (HLT) and the Foot Laterality Task (FLT), provide an example of more implicit tasks (i.e., less action monitoring is required). While, an example of a more explicit task is the Mental Motor Chronometry task (MMC) for hands and feet, where individuals are asked to perform or imagine performing movements with their limbs (i.e., more action monitoring is required). In our study, we directly compared hands and feet at all these tasks for the first time, as these body districts have different physical features as well as functions. Fifty-five participants were asked to complete an online version of the HLT and FLT (more implicit measure), and an online version of the MMC task for hands and feet (more explicit measure). The mental representation of hands and feet in action differed only when the degree of action monitoring decreased (HLT ≠ FLT); we observed the presence of biomechanical constraints only for hands. Differently, when the degree of action monitoring increased hands and feet did not show any difference (MMC hands = MMC feet). Our results show the presence of a difference in the mental representation of hands and feet in action that specifically depends on the degree of action monitoring.

Obesity is a clinical condition that impacts severely the physical body. However, evidence related to the mental representation of the body in action is scarce. The few available studies only focus on avoiding obstacles, rather than participants imagining their own body. To advance knowledge in this field, we assessed the performance of 22 individuals with obesity compared with 30 individuals with a healthy weight in two tasks that implied different motor (more implicit vs. more explicit) imagery strategies. Two tasks were also administered to control for visual imagery skills, to rule out confounding factors. Moreover, we measured body uneasiness, through a standard questionnaire, as body image negativity could impact on other body representation components. Our findings do not show differences in the motor imagery tasks between individuals with obesity and individuals with healthy weight. On the other hand, some differences emerge in visual imagery skills. Crucially, individuals with obesity did report a higher level of body uneasiness. Despite a negative body image and visual imagery differences, obesity per se does not impact on the representation of the body in action. Importantly, this result is independent from the level of awareness required to access the mental representation of the body.

Aims Spontaneous sensations (SPS) are sensations that are felt in the body in the absence of external stimulation. The literature on SPS has used explicit measures, such as questionnaires to explore SPS, while no studies to date have examined SPS on an implicit level. This study was conducted to collect representative stimuli that can be used to build such a task, for example, an Implicit Association Test. Methods An online survey was completed by 18 participants to identify the most frequent words used to describe our limbs in the presence or absence of SPS. Results Individuals who perceive and those who do not perceive SPS in their limbs describe their limbs as normal, while the most frequently described SPS were itching and tingling. Conclusions Thus, we use the same words/adjectives to describe how we perceive our limbs. However, the way we experience SPS varies as we experience more SPS in hands than feet.

Humor is a multifaceted function unique to human beings, like language and symbolic thought. Theories of humor propose different frameworks to investigate this function empirically; here, we applied a cognitive-psychology approach, focusing on a specific humor task. We asked 32 participants to listen to 30 jokes intermixed with 30 non-jokes that had an implausible ending, and to decide whether or not each stimulus was funny (Humor Decision Task, HDT). In a control task, 30 plausible stories were intermixed with 30 stories with an implausible ending and participants had to decide whether or not each stimulus was “strange” (Implausibility Decision Task, IDT). Response times (RT) in correct responses indicated that the two tasks involved different cognitive operations: while “yes, funny” responses were 256 ms faster than “no, not-funny” responses, “yes, strange” responses took the same time as “no, not-strange” ones. IDT results could be explained by assuming that participants used the degree of semantic overlap between the setup and the ending of the story to select a response. Two different cognitive accounts for the HDT results are offered, the “recognition” and the “sequential attempts” model. According to the “recognition” account,participants activate long-term memory (LTM) abstract representations of the semantic structure of jokes, while the “sequential attempts” account implies a trial-and-error strategy to find a solution to the puzzle posed by a punchline that is not already available in LTM. The RT pattern observed inincorrect responses led us to reject the “recognition” account and support the “sequential attempts” hypothesis.

Peripersonal space (PPS), the space closely surrounding the body, is typically characterised by enhanced multisensory integration. Neurophysiological and behavioural studies have consistently shown stronger visuo-tactile integration when a visual stimulus is presented close to the tactually stimulate body part in near space (within PPS) than in far space. However, in the majority of these studies, tactile stimuli were delivered to the upper limbs, torso and face. Therefore, it is not known whether the space surrounding the lower limbs is characterised by similar multisensory properties. To address this question, we asked participants to complete two versions of the classic visuo-tactile crossmodal congruency task in which they had to perform speeded elevation judgements of tactile stimuli presented to the dorsum of the hand and foot while a simultaneous visual distractor was presented at spatially congruent or incongruent locations either in near or far space. In line with existing evidence, when the tactile target was presented to the hand, the size of the crossmodal congruency effect (CCE) decreased in far as compared to near space, suggesting stronger visuo-tactile multisensory integration within PPS. In contrast, when the tactile target was presented to the foot, the CCE decreased for visual distractors in near than far space. These findings show systematic differences between the representation of PPS around upper and lower limbs, suggesting that the multisensory properties of the different body part-centred representations of PPS are likely to depend on the potential actions performed by the different body parts.

OBJECTIVE:Women with anorexia nervosa (AN) act as if they have a larger body, as evidenced in obstacle avoidance tasks, where an allocentric perspective is adopted. This alteration emerges not only when they perform, but also when they imagine movements. However, no previous study has investigated own body centered tasks. As such, in this study we aim at documenting if women with AN show an altered behaviour also when the task requires a first-person perspective.METHOD:We explored the performance of eleven woman affected by AN compared to eighteen matched controls, in two motor imagery tasks based on a self-frame of reference, the Hand Laterality Task and the Mental Motor Chronometry Task. Moreover, two control tasks relative to visual imagery were administered.RESULTS:In the Hand Laterality Task, affected participants did not adopt a motor strategy to judge hands laterality (i.e. no biomechanical constraints effect). Crucially, they also showed an altered behavior in the control task. Similarly, they did not show the expected isochrony in the Mental Motor Chronometry Task, when actions pertained the left (but not the right) hand, in absence of any difference in the control task.CONCLUSIONS:Our findings reveal altered imagery processes in AN. Specifically, affected participants adopt a third-person, rather than a first-person perspective, even when the task requires to imagine their own body in an internal frame of reference. In other words, participants with AN objectify body stimuli. Different mechanisms (i.e., checking behaviour; mirror self-reflection; altered multisensory integration) can explain such an altered imagery in AN.

The representation of the metrics of the hands is distorted, but is susceptible to malleability due to expert dexterity (magicians) and long-term tool use (baseball players). However, it remains unclear whether modulation leads to a stable representation of the hand that is adopted in every circumstance, or whether the modulation is closely linked to the spatial context where the expertise occurs. To this aim, a group of 10 experienced Sign Language (SL) interpreters were recruited to study the selective influence of expertise and space localisation in the metric representation of hands. Experiment 1 explored differences in hands' size representation between the SL interpreters and 10 age-matched controls in near-reaching (Condition 1) and far-reaching space (Condition 2), using the localisation task. SL interpreters presented reduced hand size in near-reaching condition, with characteristic underestimation of finger lengths, and reduced overestimation of hands and wrists widths in comparison with controls. This difference was lost in far-reaching space, confirming the effect of expertise on hand representations is closely linked to the spatial context where an action is performed. As SL interpreters are also experts in the use of their face with communication purposes, the effects of expertise in the metrics of the face were also studied (Experiment 2). SL interpreters were more accurate than controls, with overall reduction of width overestimation. Overall, expertise modifies the representation of relevant body parts in a specific and context-dependent manner. Hence, different representations of the same body part can coexist simultaneously.

Body representation (BR) refers to the mental representation of motor, sensory, emotional and semantic information about the physical body. This cognitive representation is used in our everyday life, continuously, even though most of the time we do not appreciate it consciously. In some cases, BR is vital to be able to communicate. A crucial feature of signed languages (SLs), for instance, is that body parts such as hands are used to communicate. Nevertheless, little is known about BR in SL: is the communicative function of the body overwriting the physical constraints? Here, we explored this question by comparing twelve British Sign Language (BSL) learners to seventeen tango dancers (body expertise but not for communication) and fourteen control subjects (no special body expertise). We administered the Body Esteem Scale (BES), the Hand Laterality Task (HLT) and the Mental Motor Chronometry (MMC). To control for visual imagery, we administered ad hoc control tasks. We did not identify parameters able to differentiate between SL users and the other groups, whereas the more implicit parameters distinguished clearly tango dancers from controls. Importantly, neither tasks on visual imagery nor the BES revealed differences. Our findings offer initial evidence that linguistic use of the body not necessarily influences the cognitive components we explored of body representation.