Just a heartbeat away from one's body: interoceptive sensitivity predicts malleability of body-representations

Body-awareness relies on the representation of both interoceptive and exteroceptive percepts coming from one's body. However, the exact relationship and possible interaction of interoceptive and exteroceptive systems for body-awareness remain unknown. We sought to understand for the first time, to our knowledge, the interaction between interoceptive and exteroceptive awareness of the body. First, we measured interoceptive awareness with an established heartbeat monitoring task. We, then, used a multi-sensory-induced manipulation of body-ownership (e.g. Rubber Hand Illusion (RHI)) and we quantified the extent to which participants experienced ownership over a foreign body-part using behavioural, physiological and introspective measures. The results suggest that interoceptive sensitivity predicts the malleability of body representations, that is, people with low interoceptive sensitivity experienced a stronger illusion of ownership in the RHI. Importantly, this effect was not simply owing to a poor proprioceptive representation or differences in autonomic states of one's body prior to the multi-sensory stimulation, suggesting that interoceptive awareness modulates the online integration of multi-sensory body-percepts.     

Strategies for integrating disparate social information

Social information use is widespread in the animal kingdom, helping individuals rapidly acquire useful knowledge and adjust to novel circumstances. In humans, the highly interconnected world provides ample opportunities to benefit from social information but also requires navigating complex social environments with people holding disparate or conflicting views. It is, however, still largely unclear how people integrate information from multiple social sources that (dis)agree with them, and among each other. We address this issue in three steps. First, we present a judgement task in which participants could adjust their judgements after observing the judgements of three peers. We experimentally varied the distribution of this social information, systematically manipulating its variance (extent of agreement among peers) and its skewness (peer judgements clustering either near or far from the participant''s judgement). As expected, higher variance among peers reduced their impact on behaviour. Importantly, observing a single peer confirming a participant''s own judgement markedly decreased the influence of other—more distant—peers. Second, we develop a framework for modelling the cognitive processes underlying the integration of disparate social information, combining Bayesian updating with simple heuristics. Our model accurately accounts for observed adjustment strategies and reveals that people particularly heed social information that confirms personal judgements. Moreover, the model exposes strong inter-individual differences in strategy use. Third, using simulations, we explore the possible implications of the observed strategies for belief updating. These simulations show how confirmation-based weighting can hamper the influence of disparate social information, exacerbate filter bubble effects and deepen group polarization. Overall, our results clarify what aspects of the social environment are, and are not, conducive to changing people''s minds.     

Body Conscious? Interoceptive Awareness,Measured by Heartbeat Perception,Is Negatively Correlated with Self-Objectification

Background

‘Self-objectification’ is the tendency to experience one''s body principally as an object, to be evaluated for its appearance rather than for its effectiveness. Within objectification theory, it has been proposed that self-objectification accounts for the poorer interoceptive awareness observed in women, as measured by heartbeat perception. Our study is, we believe, the first specifically to test this relationship.

Methodology/Principal Findings

Using a well-validated and reliable heartbeat perception task, we measured interoceptive awareness in women and compared this with their scores on the Self-Objectification Questionnaire, the Self-Consciousness Scale and the Body Consciousness Questionnaire. Interoceptive awareness was negatively correlated with self-objectification. Interoceptive awareness, public body consciousness and private body consciousness together explained 31% of the variance in self-objectification. However, private body consciousness was not significantly correlated with interoceptive awareness, which may explain the many nonsignificant results in self-objectification studies that have used private body consciousness as a measure of body awareness.

Conclusions/Significance

We propose interoceptive awareness, assessed by heartbeat perception, as a measure of body awareness in self-objectification studies. Our findings have implications for those clinical conditions, in women, which are characterised by self-objectification and low interoceptive awareness, such as eating disorders.     

Prospective memory mediated by interoceptive accuracy: a psychophysiological approach

Previous studies on prospective memory (PM), defined as memory for future intentions, suggest that psychological stress enhances successful PM retrieval. However, the mechanisms underlying this notion remain poorly understood. We hypothesized that PM retrieval is achieved through interaction with autonomic nervous activity, which is mediated by the individual accuracy of interoceptive awareness, as measured by the heartbeat detection task. In this study, the relationship between cardiac reactivity and retrieval of delayed intentions was evaluated using the event-based PM task. Participants were required to detect PM target letters while engaged in an ongoing 2-back working memory task. The results demonstrated that individuals with higher PM task performance had a greater increase in heart rate on PM target presentation. Also, higher interoceptive perceivers showed better PM task performance. This pattern was not observed for working memory task performance. These findings suggest that cardiac afferent signals enhance PM retrieval, which is mediated by individual levels of interoceptive accuracy.This article is part of the themed issue ‘Interoception beyond homeostasis: affect, cognition and mental health’.     

Interoception across modalities: on the relationship between cardiac awareness and the sensitivity for gastric functions

The individual sensitivity for ones internal bodily signals ("interoceptive awareness") has been shown to be of relevance for a broad range of cognitive and affective functions. Interoceptive awareness has been primarily assessed via measuring the sensitivity for ones cardiac signals ("cardiac awareness") which can be non-invasively measured by heartbeat perception tasks. It is an open question whether cardiac awareness is related to the sensitivity for other bodily, visceral functions. This study investigated the relationship between cardiac awareness and the sensitivity for gastric functions in healthy female persons by using non-invasive methods. Heartbeat perception as a measure for cardiac awareness was assessed by a heartbeat tracking task and gastric sensitivity was assessed by a water load test. Gastric myoelectrical activity was measured by electrogastrography (EGG) and subjective feelings of fullness, valence, arousal and nausea were assessed. The results show that cardiac awareness was inversely correlated with ingested water volume and with normogastric activity after water load. However, persons with good and poor cardiac awareness did not differ in their subjective ratings of fullness, nausea and affective feelings after drinking. This suggests that good heartbeat perceivers ingested less water because they subjectively felt more intense signals of fullness during this lower amount of water intake compared to poor heartbeat perceivers who ingested more water until feeling the same signs of fullness. These findings demonstrate that cardiac awareness is related to greater sensitivity for gastric functions, suggesting that there is a general sensitivity for interoceptive processes across the gastric and cardiac modality.     

The role of observers' gaze behaviour when watching object manipulation tasks: predicting and evaluating the consequences of action

When watching an actor manipulate objects, observers, like the actor, naturally direct their gaze to each object as the hand approaches and typically maintain gaze on the object until the hand departs. Here, we probed the function of observers'' eye movements, focusing on two possibilities: (i) that observers'' gaze behaviour arises from processes involved in the prediction of the target object of the actor''s reaching movement and (ii) that this gaze behaviour supports the evaluation of mechanical events that arise from interactions between the actor''s hand and objects. Observers watched an actor reach for and lift one of two presented objects. The observers'' task was either to predict the target object or judge its weight. Proactive gaze behaviour, similar to that seen in self-guided action–observation, was seen in the weight judgement task, which requires evaluating mechanical events associated with lifting, but not in the target prediction task. We submit that an important function of gaze behaviour in self-guided action observation is the evaluation of mechanical events associated with interactions between the hand and object. By comparing predicted and actual mechanical events, observers, like actors, can gain knowledge about the world, including information about objects they may subsequently act upon.     

Differential Reward Learning for Self and Others Predicts Self-Reported Altruism

In social environments, decisions not only determine rewards for oneself but also for others. However, individual differences in pro-social behaviors have been typically studied through self-report. We developed a decision-making paradigm in which participants chose from card decks with differing rewards for themselves and charity; some decks gave similar rewards to both, while others gave higher rewards for one or the other. We used a reinforcement-learning model that estimated each participant''s relative weighting of self versus charity reward. As shown both in choices and model parameters, individuals who showed relatively better learning of rewards for charity – compared to themselves – were more likely to engage in pro-social behavior outside of a laboratory setting indicated by self-report. Overall rates of reward learning, however, did not predict individual differences in pro-social tendencies. These results support the idea that biases toward learning about social rewards are associated with one''s altruistic tendencies.     

Dynamic visual cues induce jaw opening and closing by tiger beetles during pursuit of prey

In dynamic locomotory contexts, visual cues often trigger adaptive behaviour by the viewer, yet studies investigating how animals determine impending collisions typically employ either stationary viewers or objects. Here, we describe a dynamic situation of visually guided prey pursuit in which both impending prey contact and escape elicit observable adaptive behaviours in the pursuer, a predatory beetle. We investigated which visual cues may independently control opening and closing of the beetle''s jaws during chases of prey dummies. Jaw opening and closing typically occur when prey is within the 60° binocular field, but not at specific distances, angular sizes or time-to-collision. We show that a sign change in the expansion rate of the target image precedes jaw opening (16 ms) and closing (35 ms), signalling to the beetle that it is gaining on the target or that the target is getting away. We discuss the ‘sloppiness'' of such variation in the lag of the behavioural response, especially jaw closing, as an adaptation to uncertainty about target position due to degradation of the target image by motion blur from the fast-running beetle.     

The relationship between social behaviour and habitat familiarity in African elephants (Loxodonta africana)

Social associations with conspecifics can expedite animals'' acclimation to novel environments. However, the benefits gained from sociality may change as the habitat becomes familiar. Furthermore, the particular individuals with whom animals associate upon arrival at a new place, familiar conspecifics or knowledgeable unfamiliar residents, may influence the type of information they acquire about their new home. To examine animals'' social dynamics in novel habitats, we studied the social behaviour of African elephants (Loxodonta africana) translocated into a novel environment. We found that the translocated elephants'' association with conspecifics decreased over time supporting our hypothesis that sociality provides added benefits in novel environments. In addition, we found a positive correlation between body condition and social association, suggesting that elephants gain direct benefits from sociality. Furthermore, the translocated elephants associated significantly less than expected with the local residents and more than expected with familiar, but not necessarily genetically related, translocated elephants. The social segregation between the translocated and resident elephants declined over time, suggesting that elephants can integrate into an existing social setting. Knowledge of the relationship between sociality and habitat familiarity is highly important in our constantly changing world to both conservation practice and our understanding of animals'' behaviour in novel environments.     

Social orienting in gaze leading: a mechanism for shared attention

Here, we report a novel social orienting response that occurs after viewing averted gaze. We show, in three experiments, that when a person looks from one location to an object, attention then shifts towards the face of an individual who has subsequently followed the person''s gaze to that same object. That is, contrary to ‘gaze following’, attention instead orients in the opposite direction to observed gaze and towards the gazing face. The magnitude of attentional orienting towards a face that ‘follows’ the participant''s gaze is also associated with self-reported autism-like traits. We propose that this gaze leading phenomenon implies the existence of a mechanism in the human social cognitive system for detecting when one''s gaze has been followed, in order to establish ‘shared attention’ and maintain the ongoing interaction.     

When dogs look back: inhibition of independent problem-solving behaviour in domestic dogs (Canis lupus familiaris) compared with wolves (Canis lupus)

Domestic dogs have been recognized for their social sensitivity and aptitude in human-guided tasks. For example, prior studies have demonstrated that dogs look to humans when confronted with an unsolvable task; an action often interpreted as soliciting necessary help. Conversely, wolves persist on such tasks. While dogs'' ‘looking back’ behaviour has been used as an example of socio-cognitive advancement, an alternative explanation is that pet dogs show less persistence on independent tasks more generally. In this study, pet dogs, shelter dogs and wolves were given up to three opportunities to open a solvable puzzle box: when subjects were with a neutral human caretaker, alone and when encouraged by the human. Wolves were more persistent and more successful on this task than dogs, with 80% average success rate for wolves versus a 5% average success rate for dogs in both the human-in and alone conditions. Dogs showed increased contact with the puzzle box during the encouragement condition, but only a moderate increase in problem-solving success. Social sensitivity appears to play an important role in pet and shelter dogs'' willingness to engage in problem-solving behaviour, which could suggest generalized dependence on, or deference to, human action.     

Identification of Direct and Indirect Social Network Effects in the Pathophysiology of Insulin Resistance in Obese Human Subjects

Objective

The aim of the present study was to examine to what extent different social network mechanisms are involved in the pathogenesis of obesity and insulin-resistance.

Design

We used nonparametric and parametric regression models to analyse whether individual BMI and HOMA-IR are determined by social network characteristics.

Subjects and Methods

A total of 677 probands (EGO) and 3033 social network partners (ALTER) were included in the study. Data gathered from the probands include anthropometric measures, HOMA-IR index, health attitudes, behavioural and socio-economic variables and social network data.

Results

We found significant treatment effects for ALTERs frequent dieting (p<0.001) and ALTERs health oriented nutritional attitudes (p<0.001) on EGO''s BMI, establishing a significant indirect network effect also on EGO''s insulin resistance. Most importantly, we also found significant direct social network effects on EGO''s insulin resistance, evidenced by an effect of ALTERs frequent dieting (p = 0.033) and ALTERs sport activities (p = 0.041) to decrease EGO''s HOMA-IR index independently of EGO''s BMI.

Conclusions

Social network phenomena appear not only to be relevant for the spread of obesity, but also for the spread of insulin resistance as the basis for type 2 diabetes. Attitudes and behaviour of peer groups influence EGO''s health status not only via social mechanisms, but also via socio-biological mechanisms, i.e. higher brain areas might be influenced not only by biological signals from the own organism, but also by behaviour and knowledge from different human individuals. Our approach allows the identification of peer group influence controlling for potential homophily even when using cross-sectional observational data.     

The Impact of Social Context and Language Comprehension on Behaviour: A Kinematic Investigation

We investigated whether and how comprehending sentences that describe a social context influences our motor behaviour. Our stimuli were sentences that referred to objects having different connotations (e.g., attractive/ugly vs. smooth/prickly) and that could be directed towards the self or towards “another person” target (e.g., “The object is ugly/smooth. Bring it to you/Give it to another person”). Participants judged whether each sentence was sensible or non-sensible by moving the mouse towards or away from their body. Mouse movements were analysed according to behavioral and kinematics parameters. In order to enhance the social meaning of the linguistic stimuli, participants performed the task either individually (Individual condition) or in a social setting, in co-presence with the experimenter. The experimenter could either act as a mere observer (Social condition) or as a confederate, interacting with participants in an off-line modality at the end of task execution (Joint condition). Results indicated that the different roles taken by the experimenter affected motor behaviour and are discussed within an embodied approach to language processing and joint actions.     

The Importance of the Derivative in Sex-Hormone Cycles: A Reason Why Behavioural Measures in Sex-Hormone Studies Are So Mercurial

To study the dynamic changes in cognition across the human menstrual cycle, twenty, healthy, naturally-cycling women undertook a lateralized spatial figural comparison task on twelve occasions at approximately 3–4 day intervals. Each session was conducted in laboratory conditions with response times, accuracy rates, eye movements, salivary estrogen and progesterone concentrations and Profile of Mood states questionnaire data collected on each occasion. The first two sessions of twelve for the response variables were discarded to avoid early effects of learning thereby providing 10 sessions spread across each participant''s complete menstrual cycle. Salivary progesterone data for each participant was utilized to normalize each participant''s data to a standard 28 day cycle. Data was analysed categorically by comparing peak progesterone (luteal phase) to low progesterone (follicular phase) to emulate two-session repeated measures typical studies. Neither a significant difference in reaction times or accuracy rates was found. Moreover no significant effect of lateral presentation was observed upon reaction times or accuracy rates although inter and intra individual variance was sizeable. We demonstrate that hormone concentrations alone cannot be used to predict the response times or accuracy rates. In contrast, we constructed a standard linear model using salivary estrogen, salivary progesterone and their respective derivative values and found these inputs to be very accurate for predicting variance observed in the reaction times for all stimuli and accuracy rates for right visual field stimuli but not left visual field stimuli. The identification of sex-hormone derivatives as predictors of cognitive behaviours is of importance. The finding suggests that there is a fundamental difference between the up-surge and decline of hormonal concentrations where previous studies typically assume all points near the peak of a hormonal surge are the same. How contradictory findings in sex-hormone research may have come about are discussed.     

Self-Knowledge Dim-Out: Stress Impairs Metacognitive Accuracy

Modulation of frontal lobes activity is believed to be an important pathway trough which the hypothalamic-pituitary-adrenal (HPA) axis stress response impacts cognitive and emotional functioning. Here, we investigate the effects of stress on metacognition, which is the ability to monitor and control one''s own cognition. As the frontal lobes have been shown to play a critical role in metacognition, we predicted that under activation of the HPA axis, participants should be less accurate in the assessment of their own performances in a perceptual decision task, irrespective of the effect of stress on the first order perceptual decision itself. To test this prediction, we constituted three groups of high, medium and low stress responders based on cortisol concentration in saliva in response to a standardized psycho-social stress challenge (the Trier Social Stress Test). We then assessed the accuracy of participants'' confidence judgments in a visual discrimination task. As predicted, we found that high biological reactivity to stress correlates with lower sensitivity in metacognition. In sum, participants under stress know less when they know and when they do not know.     

Losing One's Hand: Visual-Proprioceptive Conflict Affects Touch Perception

Background

While the sense of bodily ownership has now been widely investigated through the rubber hand illusion (RHI), very little is known about the sense of disownership. It has been hypothesized that the RHI also affects the ownership feelings towards the participant''s own hand, as if the rubber hand replaced the participant''s actual hand. Somatosensory changes observed in the participants'' hand while experiencing the RHI have been taken as evidence for disownership of their real hand. Here we propose a theoretical framework to disambiguate whether such somatosensory changes are to be ascribed to the disownership of the real hand or rather to the anomalous visuo-proprioceptive conflict experienced by the participant during the RHI.

Methodology/Principal Findings

In experiment 1, reaction times (RTs) to tactile stimuli delivered to the participants'' hand slowed down following the establishment of the RHI. In experiment 2, the misalignment of visual and proprioceptive inputs was obtained via prismatic displacement, a situation in which ownership of the seen hand was doubtless. This condition slowed down the participants'' tactile RTs. Thus, similar effects on touch perception emerged following RHI and prismatic displacement. Both manipulations also induced a proprioceptive drift, toward the fake hand in the first experiment and toward the visual position of the participants'' hand in the second experiment.

Conclusions/Significance

These findings reveal that somatosensory alterations in the experimental hand resulting from the RHI result from cross-modal mismatch between the seen and felt position of the hand. As such, they are not necessarily a signature of disownership.     

The body beyond the body: expectation of a sensory event is enough to induce ownership over a fake hand

More than 100 papers have been published on the rubber hand illusion since its discovery 14 years ago. The illusion has been proposed as a demonstration that the body is distinguished from other objects by its participation in specific forms of intermodal perceptual correlation. Here, we radically challenge this view by claiming that perceptual correlation is not necessary to produce the experience of this body as mine. Each of 15 participants was seated with his/her right arm resting upon a table just below another smaller table. Thus, the real hand was hidden from the participant''s view and a life-sized rubber model of a right hand was placed on the small table in front of the participant. The participant observed the experimenter''s hand while approaching—without touching—the rubber hand. Phenomenology of the illusion was measured by means of skin conductance response and questionnaire. Both measures indicated that participants experienced the illusion that the experimenter''s hand was about to touch their hidden hand rather than the rubber hand, as if the latter replaced their own hand. This did not occur when the rubber hand was rotated by 180° or replaced by a piece of wood. This illusion indicates that our brain does not build a sense of self in a merely reactive way, via perceptual correlations; rather it generates predictions on what may or may not belong to itself.     

Dogs' Social Referencing towards Owners and Strangers

Social referencing is a process whereby an individual uses the emotional information provided by an informant about a novel object/stimulus to guide his/her own future behaviour towards it. In this study adult dogs were tested in a social referencing paradigm involving a potentially scary object with either their owner or a stranger acting as the informant and delivering either a positive or negative emotional message. The aim was to evaluate the influence of the informant''s identity on the dogs'' referential looking behaviour and behavioural regulation when the message was delivered using only vocal and facial emotional expressions. Results show that most dogs looked referentially at the informant, regardless of his/her identity. Furthermore, when the owner acted as the informant dogs that received a positive emotional message changed their behaviour, looking at him/her more often and spending more time approaching the object and close to it; conversely, dogs that were given a negative message took longer to approach the object and to interact with it. Fewer differences in the dog''s behaviour emerged when the informant was the stranger, suggesting that the dog-informant relationship may influence the dog''s behavioural regulation. Results are discussed in relation to studies on human-dog communication, attachment, mood modification and joint attention.     

Perching of Tengmalm's Owl (Aegolius funereus) Nestlings at the Nest Box Entrance: Effect of Time of the Day,Age, Wing Length and Body Weight

The behaviour of the nestlings of nocturnal cavity-nesting species has relatively rarely been studied in detail because of problems connected with use of the technical devices required to provide long-term monitoring of individuals. However, long-term observation of nestling behaviour is crucial in order to identify different types of behaviour which may be caused by sibling competition at the end of nesting period. We studied behaviour of 43 Tengmalm''s owl (Aegolius funereus) nestlings at 14 nests using a camera and a chip system. The nestlings perched at the nest box entrance from an average age of 28 days from hatching (range 24–34 days) until fledging, spending around 2 hours per day here in total, in periods ranging from a few seconds to 147 min (7.6±10.9 min, mean ± SD). We found that individual duration of perching at the nest box entrance was significantly influenced by nestlings'' age and wing length and that the duration of perching at the nest box entrance significantly decreased with time of night. However, during daylight hours, time of day had no effect on either probability or duration of nestlings'' perching. We suggest daylight perching at the nest box entrance results from nestlings'' preparation for fledging, while individuals perching here during the night may gain an advantageous position for obtaining food from the parents; another possibility at all times of day is that nestlings can reaffirm their social dominance status by monopolizing the nest box entrance.     

Effects of Haptic Information on the Perception of Dynamic 3-D Movement

This study examined effects of hand movement on visual perception of 3-D movement. I used an apparatus in which a cursor position in a simulated 3-D space and the position of a stylus on a haptic device could coincide using a mirror. In three experiments, participants touched the center of a rectangle in the visual display with the stylus of the force-feedback device. Then the rectangle''s surface stereoscopically either protruded toward a participant or indented away from the participant. Simultaneously, the stylus either pushed back participant''s hand, pulled away, or remained static. Visual and haptic information were independently manipulated. Participants judged whether the rectangle visually protruded or dented. Results showed that when the hand was pulled away, subjects were biased to perceive rectangles indented; however, when the hand was pushed back, no effect of haptic information was observed (Experiment 1). This effect persisted even when the cursor position was spatially separated from the hand position (Experiment 2). But, when participants touched an object different from the visual stimulus, this effect disappeared (Experiment 3). These results suggest that the visual system tried to integrate the dynamic visual and haptic information when they coincided cognitively, and the effect of haptic information on visually perceived depth was direction-dependent.