Does hunger sharpen senses? A psychophysics investigation on the effects of appetite in the timing of reinforcement-oriented actions

Individual predictors of vaccine hesitancy in the Italian post COVID-19 pandemic era

A wide range of survey studies have explored vaccination hesitancy/resistance during the COVID-19 pandemic and provided evidence that this can be explained by several individual variables from the ideological, clinical, and socio-affective domain. However, evidence about which individual variables predict vaccine hesitancy in the post-pandemic state of COVID-19 is meager. We administered a battery of questionnaires to a group of 120 Italian participants with high and low scores on the adult vaccine hesitancy scale (aVHS) to investigate the predictive role of ideological (i.e. political orientation), clinical (i.e. anxiety, interoceptive accuracy), and socio-affective (i.e. alexithymia, disgust sensitivity/propensity, empathy) variables on vaccine hesitancy/resistance. This study provides evidence that lower interoceptive awareness and cognitive empathy are predictors of a greater hesitancy to get vaccinated in the post-pandemic COVID-19 state.

Neurophysiological evidence of motor contribution to vicarious affective touch

Understanding observed interpersonal touch, particularly the so-called affective touch targeting the CT fibers, is essential for social interactions. Research has documented that observing other people being touched activates the same cortical areas involved in direct tactile experiences. However, observing interpersonal touch also activates an inner simulation of the movements in the observer's motor system. Given the social and affective significance of CT-optimal touch, the present study tested the hypothesis that observing stroking touches targeting or not targeting the CT fibers system might distinctly influence motor resonance to vicarious touch. With this aim, we used single-pulse transcranial magnetic stimulation and motor-evoked potentials recording while participants observed video clips of interpersonal touch events at different stroking velocities. We found a modulation of motor system activity, particularly a decrease in corticospinal excitability, when observing CT-optimal touch as opposed to non-CT-optimal velocities, a mechanism that might aid in understanding the touchee's feelings during vicarious interpersonal touch. Moreover, participants with higher reliance on bodily cues to be emotionally aware showed greater motor suppression for CT-optimal compared to non-CT-optimal velocities. These results shed light on the complex interplay between motor and somatosensory systems in social touch perception and emphasize the importance of affective touch in human social interactions.

To touch or to be touched? comparing appraisal of vicarious execution and reception of interpersonal touch

Unmyelinated C-Tactile (CT) fibres are activated by caress-like touch, eliciting a pleasant feeling that decreases for static and faster stroking. Previous studies documented this effect also for vicarious touch, hypothesising simulation mechanisms driving the perception and appreciation of observed interpersonal touch. Notably, less is known about appreciation of vicarious execution of touch, that is as referred to the one giving gentle touch. To address this issue, 53 healthy participants were asked to view and rate a series of videoclips displaying an individual being touched by another on hairy (i.e., hand dorsum) or glabrous (i.e., palm) skin sites, with touch being delivered at CT-optimal (5 cm/s) or non-CT optimal velocities (0 cm/s or 30 cm/s). Following the observation of each clip, participants were asked to rate self-referred desirability and model-referred pleasantness of vicarious touch for both executer (toucher-referred) and receiver (touchee-referred). Consistent with the CT fibres properties, for both self-referred desirability and model-referred pleasantness judgements of vicarious touch execution and reception, participants provided higher ratings for vicarious touch delivered at CT-optimal than other velocities, and when observed CT-optimal touch was delivered to the hand-dorsum compared to the palm. However, higher ratings were attributed to vicarious reception compared to execution of CT-optimal touch. Notably, individual differences in interoceptive trusting and attitude to interpersonal touch were positively correlated with, respectively, toucher- and touchee-related overall appraisal ratings of touch. These findings suggest that the appreciation of both toucher- and touchee-referred vicarious touch is specifically attuned to CT-optimal touch, even though they might rely on different neurocognitive mechanisms to understand affective information conveyed by interpersonal tactile interactions.

Stressed individuals exhibit pessimistic bursting beliefs and a lower risk preference in the balloon analogue risk task

Stress alters decision-making by usually promoting risk-taking and reward-seeking, which could be advantageous in a context where risk is rewarded, such as the Balloon Analogue Risk Task (BART). However, previous studies addressing this issue showed inconsistencies which could emerge from assessing decision-making as a single dimension. Our aim is to study through computational modelling how stress influences cognitive subprocesses of the decision-making during the BART. For this purpose, 94 healthy participants were submitted to BART, but only half were exposed to the virtual Trier Social Stress Test (TSST-VR). The Experimental-Weight Mean-Variance (EWMV) model was used to gain insight into the subprocesses involved in risk-taking during BART. Rather than reward-seeking, our results showed a pessimistic prior belief about the balloons bursting likelihood, and a lower risk preference in the stressed participants. This cautious attitude could be attributable to an alertness state promoted by stress. Yet, since risk is rewarded in BART, it could also evidence a maladaptive decision-making derived from learning difficulties and altered feedback-processing under stress.

‘When hunger makes everything better looking!’: The effect of hunger on the aesthetic appreciation of human bodies, faces and objects

Background

Research evidence suggests that physiological state of hunger might affect preference for female body weight, such that hungrier, compared to satiate, men prefer heavier body weight and rate as more attractive heavier female figures. Here, we seek to extend these findings by comparing the effects of fasting and snack on aesthetics judgements of the bodies and faces of conspecifics and of objects in a sample of female and male participants.

Methods

Forty-four participants (women: n = 21, mean age = 23.70 yrs ± 0.62) provided aesthetic liking judgments of round and slim human bodies, faces and objects, under at least 12 h of overnight fasting and immediately after having eaten a snack (i.e., bananas). An anthropometric measure of adiposity (i.e., Body Mass Index, BMI) was also collected from each observer.

Results

Overall, we found that participants’ aesthetic judgements were higher for slim stimuli compared to round ones. However, after fasting, participants rated round stimuli as more attractive compared to when they had a snack. This hunger-based shift in ratings not only was apparent when stimuli depicted a human body or face, but also when they depicted an object, thus suggesting a general modification of observers’ aesthetic preference related to hunger. Importantly, this effect was modulated by participants’ BMI so that only participants with a high BMI provided higher aesthetic judgements for round stimuli after fasting than after a snack.

Conclusions

Our results demonstrated that both the modification of the physiological state and the individual differences in adiposity level of the observers might affect the aesthetic appreciation of the external world.

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.

Time is body: Multimodal evidence of crosstalk between interoception and time estimation

Theoretical approaches propose a blending between interoception and time estimation. Interoception might constitute a neurophysiological mechanism for encoding duration. However, no study has assessed the convergence between interoception and time estimation using behavioral, neurophysiological, and functional anatomy signatures. We examined the multimodal convergence between interoception and time estimation using a two-fold approach. In study 1, we developed a dual design combining interoception (measuring heartbeat detection - HBD, and heartbeat evoked potential - HEP) with a time estimation paradigm (TEP, estimation of duration of a 120 s interval). In study 2, we performed a conjoint metanalysis (Multi-level Kernel Density Analysis, MKDA) of neuroimaging, including reports of interoception and time estimation. Both studies provide convergent evidence of time estimation's significant involvement in behavioral, electrophysiological (enhanced HEP), and neuroimaging (overlapping cluster in the right insula and operculum) signatures of interoception. Convergent results from both studies offer direct support for a shared mechanism of interoception and time estimation.

Does food deprivation affect perceived size?

Exposure to food-related stimuli could lead to the triggering of a set of biological, emotional and cognitive responses. Such responses can be pronounced following food deprivation. Indeed, previous research showed that even a moderate period of food deprivation is sufficient to increase perceptual precision to detect changes along food size and to change the processing style of food-related stimuli. It is unclear, however, whether food deprivation also leads to systematic biases along the perception of food size. Here, we used two classic psychophysical methods, the method of constant stimuli and the method of adjustment, adapted to the field of food perception, to study the effect of food deprivation on average perceived food size. In two experiments, food deprived and non-deprived participants were asked to compare a series of food and non-food visual stimuli along their size. The results were inconsistent and depended upon the method used. When found, small bias effects resulted in food stimuli perceived as bigger following food deprivation. The results show that unlike the reliable effects motivational factors have on perceptual precision and on perceptual processing style, they have an inconsistent influence on average perceived food size.

Time Processing, Interoception, and Insula Activation: A Mini-Review on Clinical Disorders

Time processing is a multifaceted skill crucial for managing different aspects of life. In the current work, we explored the relationship between interoception and time processing by examining research on clinical models. We investigated whether time processing deficits are associated with dysfunction of the interoceptive system and/or insular cortex activity, which is crucial in decoding internal body signaling. Furthermore, we explored whether insular activation predicts the subjective experience of time (i.e., the subjective duration of a target stimulus to be timed). Overall, our work suggests that alteration of the interoceptive system could be a common psychophysiological hallmark of mental disorders affected by time processing deficits.

Time is overestimated in obesity: A cohort study

Food addiction and high impulsivity are common traits in obesity. In accordance with the evidence that time is overestimated in patients with a history of impulsivity and/or drug addiction, we tested the hypothesis that duration is overestimated in obesity. A total of 92 obese participants and 182 healthy controls completed a timing task of visual stimuli. In line with our prediction, obese participants overestimated the duration of the displayed visual stimuli than controls. Our result has potential clinical implications in the field of obesity, as it suggests a potential contribution of this cognitive dysfunction in the emergence and maintenance of obesity-related behaviour.

The effect of hunger and satiety in the judgment of ethical violations

Human history is studded with instances where instinctive motivations take precedence over ethical choices. Nevertheless, the evidence of any linking between motivational states and morality has never been systematically explored. Here we addressed this topic by testing a possible linking between appetite and moral judgment. We compared moral disapproval ratings (MDR) for stories of ethical violations in participants under fasting and after having eaten a snack. Our results show that subjective hunger, measured via self-reported rating, reduces MDR for ethical violations. Moreover, the higher the disgust sensitivity the higher the MDR for ethical violations. This study adds new insights to research on physiological processes influencing morality by showing that appetite affects moral disapproval of ethical violations.

The Perception of Time Is Underestimated in Adolescents With Anorexia Nervosa

Research has revealed reduced temporal discounting (i.e., increased capacity to delay reward) and altered interoceptive awareness in anorexia nervosa (AN). In line with the research linking temporal underestimation with a reduced tendency to devalue a reward and reduced interoceptive awareness, we tested the hypothesis that time duration might be underestimated in AN. Our findings revealed that patients with AN displayed lower timing accuracy in the form of timing underestimation compared with controls. These results were not predicted by clinical, demographic factors, attention, and working memory performance of the participants. The evidence of a temporal underestimation bias in AN might be clinically relevant to explain their abnormal motivation in pursuing a long-term restrictive diet, in line with the evidence that increasing the subjective temporal proximity of remote future goals can boost motivation and the actual behavior to reach them.