Marco Tullio Liuzza

Follow My Eyes: The Gaze of Politicians Reflexively Captures the Gaze of Ingroup Voters

Studies in human and non-human primates indicate that basic socio-cognitive operations are inherently linked to the power of gaze in capturing reflexively the attention of an observer. Although monkey studies indicate that the automatic tendency to follow the gaze of a conspecific is modulated by the leader-follower social status, evidence for such effects in humans is meager. Here, we used a gaze following paradigm where the directional gaze of right- or left-wing Italian political characters could influence the oculomotor behavior of ingroup or outgroup voters. We show that the gaze of Berlusconi, the right-wing leader currently dominating the Italian political landscape, potentiates and inhibits gaze following behavior in ingroup and outgroup voters, respectively. Importantly, the higher the perceived similarity in personality traits between voters and Berlusconi, the stronger the gaze interference effect. Thus, higher-order social variables such as political leadership and affiliation prepotently affect reflexive shifts of attention.

Do Not Resonate with Actions: Sentence Polarity Modulates Cortico-Spinal Excitability during Action-Related Sentence Reading

Background Theories of embodied language suggest that the motor system is differentially called into action when processing motor-related versus abstract content words or sentences. It has been recently shown that processing negative polarity action-related sentences modulates neural activity of premotor and motor cortices. Methods and Findings We sought to determine whether reading negative polarity sentences brought about differential modulation of cortico-spinal motor excitability depending on processing hand-action related or abstract sentences. Facilitatory paired-pulses Transcranial Magnetic Stimulation (pp-TMS) was applied to the primary motor representation of the right-hand and the recorded amplitude of induced motor-evoked potentials (MEP) was used to index M1 activity during passive reading of either hand-action related or abstract content sentences presented in both negative and affirmative polarity. Results showed that the cortico-spinal excitability was affected by sentence polarity only in the hand-action related condition. Indeed, in keeping with previous TMS studies, reading positive polarity, hand action-related sentences suppressed cortico-spinal reactivity. This effect was absent when reading hand action-related negative polarity sentences. Moreover, no modulation of cortico-spinal reactivity was associated with either negative or positive polarity abstract sentences. Conclusions Our results indicate that grammatical cues prompting motor negation reduce the cortico-spinal suppression associated with affirmative action sentences reading and thus suggest that motor simulative processes underlying the embodiment may involve even syntactic features of language.

Rubber hand illusion highlights massive visual capture and sensorimotor face-hand remapping in a tetraplegic man

PURPOSE The illusory ownership of a fake hand as part the body follows synchronous tactile stimulation over a visible rubber hand and a covered hand. Whether brain plasticity mechanisms after sensory and motor disconnection modulates this illusion remain unexplored. METHODS We tested a tetraplegic man after synchronous and asynchronous stimulation of the hand and face. RESULTS The illusory ownership of the fake hand was tested four times in separate days and always reported. To verify whether this ownership feeling generalized also to object not resembling the human body we tested this illusion with a plastic bottle and a rubber hand. The illusionary perception of owning an external object using the rubber hand paradigm showed that the temporally matched tactile stimulation on a fake hand and visual capture mechanism create the illusionary feeling that the rubber hand was part of his body. CONCLUSIONS Despite lesions that dramatically disconnect the access to sensory inputs and motor outputs our data suggests a strong visual capture of a rubber hand and a possible remapping of hand-face representations after the spinal lesion. We suggest that vision and brain plasticity may represent a supportive tool for motor rehabilitation in patients with sensory deficits.

Kids observing other kids’ hands: Visuomotor priming in children

We investigated motor resonance in children using a priming paradigm. Participants were asked to judge the weight of an object shortly primed by a hand in an action-related posture (grasp) or a non action-related one (fist). The hand prime could belong to a child or to an adult. We found faster response times when the object was preceded by a grasp hand posture (motor resonance effect). More crucially, participants were faster when the prime was a childs hand, suggesting that it could belong to their body schema, particularly when the childs hand was followed by a light object (motor simulation effect). A control experiment helped us to clarify the role of the hand prime. To our knowledge this is the first behavioral evidence of motor simulation and motor resonance in children. Implications of the results for the development of the sense of body ownership and for conceptual development are discussed.

rTMS-induced virtual lesion of the posterior parietal cortex (PPC) alters the control of reflexive shifts of social attention triggered by pointing hands

In highly social groups like human and non-human primates, gaze and pointing cues are fundamentally important for directing the attention of conspecifics. Although neuroimaging studies indicate that shifts of attention triggered by observation of social cues activate the onlookers׳ fronto-parietal cortices, information on whether these regions play a causative role in orienting and re-orienting of social attention is lacking. To advance our understanding of this, we used event-related repetitive dual pulse transcranial magnetic stimulation to interfere with neural activity in the right frontal eye field (rFEF) and posterior parietal cortex (rPPC). This procedure allowed us to explore how inhibiting rFEF and rPPC influences shifts of attention triggered by the observation of body-related (gaze and hand) and non body-related (arrow) directional distractors. Participants were asked to perform a leftward or rightward pointing movement according to the color change of a central imperative signal while ignoring a distractor, which was either a gaze, a pointing hand or an arrow. Stimulation of rPPC in a region supposedly linked to attentional re-orienting and to planning and execution of upper limb movements increased the reflexive tendency to follow distracting pointing hands but not oriented gaze or arrows. These findings suggest that inhibition of cortical structures that control attentional shifts triggered by social stimuli brings forth an increase of the cost of attentional re-orienting. Moreover, our results provide the first causative evidence that reflexive social attention in humans may be coded according to body-part-centered frames of reference.

Subliminal perception of others’ physical pain and pleasure

Abstract Studies indicate that explicit and implicit processing of affectively charged stimuli may be reflected in specific behavioral markers and physiological signatures. This study investigated whether the pleasantness ratings of a neutral target were affected by subliminal perception of pleasant and painful facial expressions. Participants were presented images depicting face of non-famous models being slapped (painful condition), caressed (pleasant condition) or touched (neutral condition) by the right hand of another individual. In particular, we combined the continuous flash suppression technique with the affective misattribution procedure (AMP) to explore subliminal empathic processing. Measures of pupil reactivity along with empathy traits were also collected. Results showed that participants rated the neutral target as less or more likeable congruently with the painful or pleasant facial expression presented, respectively. Pupil dilation was associated both with the implicit attitudes (AMP score) and with empathic concern. Thus, the results provide behavioral and physiological evidence that state-related empathic reactivity can occur at an entirely subliminal level and that it is linked to autonomic responses and empathic traits.

The attracting power of the gaze of politicians is modulated by the personality and ideological attitude of their voters: a functional magnetic resonance imaging study

Observing someone rapidly moving their eyes induces reflexive shifts of overt and covert attention in the onlooker. Previous studies have shown that this process can be modulated by the onlookers personality, as well as by the social features of the person depicted in the cued face. Here, we investigated whether an individuals preference for social dominance orientation, in‐group perceived similarity (PS), and political affiliation of the cued‐face modulated neural activity within specific nodes of the social attention network. During functional magnetic resonance imaging, participants were requested to perform a gaze‐following task to investigate whether the directional gaze of various Italian political personages might influence the oculomotor behaviour of in‐group or out‐group voters. After scanning, we acquired measures of PS in personality traits with each political personage and preference for social dominance orientation. Behavioural data showed that higher gaze interference for in‐group than out‐group political personages was predicted by a higher preference for social hierarchy. Higher blood oxygenation level‐dependent activity in incongruent vs. congruent conditions was found in areas associated with orienting to socially salient events and monitoring response conflict, namely the left frontal eye field, right supramarginal gyrus, mid‐cingulate cortex and left anterior insula. Interestingly, higher ratings of PS with the in‐group and less preference for social hierarchy predicted increased activity in the left frontal eye field during distracting gaze movements of in‐group as compared with out‐group political personages. Our results suggest that neural activity in the social orienting circuit is modulated by higher‐order social dimensions, such as in‐group PS and individual differences in ideological attitudes.

Fortunes and misfortunes of political leaders reflected in the eyes of their electors

Gaze-following is a pivotal social behaviour that, although largely automatic, is permeable to high-order variables like political affiliation. A few years ago we reported that the gaze of Italian right-wing voters was selectively captured by the gaze of their leader Silvio Berlusconi. This effect was particularly evident in voters who saw themselves as similar to Berlusconi. Two years later, we were able to run the present follow-up study because Berlusconi’s popularity had drastically dropped due to sex and political scandals, and he resigned from office. In a representative subsample of our original group, we investigated whether perceived similarity and gaze-following reflected Berlusconi’s loss in popularity. We were also able to test the same hypothesis in an independent group of right-wing voters when their leader, Renata Polverini, resigned as Governor of ‘Regione Lazio’ due to political scandals. Our results show that the leaders’ fall in popularity paralleled the reduction of their gaze’s attracting power, as well as the decrease in similarity perceived by their voters. The less similar right-wing voters felt to their leader, the less they followed his/her gaze. Thus, the present experimental findings suggest that gaze-following can be modulated by complex situational and dispositional factors such as leader’s popularity and voter–leader perceived similarity.

The Body Odor Disgust Scale (BODS): Development and Validation of a Novel Olfactory Disgust Assessment

Disgust plays a crucial role in the avoidance of pathogen threats. In many species, body odors provide important information related to health and disease, and body odors are potent elicitors of disgust in humans. With this background, valid assessments of body odor disgust sensitivity are warranted. In the present article, we report the development and psychometric validation of the Body Odor Disgust Scale (BODS), a measure suited to assess individual differences in disgust reaction to a variety of body odors. Collected data from 3 studies (total n = 528) show that the scale can be used either as a unidimensional scale or as a scale that reflects two hypothesized factors: sensitivity to ones own body odors versus those of others. Guided by our results, we reduced the scale to 12 items that capture the essence of these 2 factors. The final version of the BODS shows an excellent internal consistency (Cronbachs αs > 0.9). The BODS subscales show convergent validity with other general disgust scales, as well as with other olfactory functions measures and with aspects of personality that are related to pathogen avoidance. A fourth study confirmed the construct validity of the BODS and its measurement invariance to gender. Moreover, we found that, compared with other general disgust scales, the BODS is more strongly related to perceived vulnerability to disease. The BODS is a brief and valid assessment of trait body odor disgust sensitivity.

Manipulating the alpha level cannot cure significance testing

We argue that making accept/reject decisions on scientific hypotheses, including a recent call for changing the canonical alpha level from p = 0.05 to p = 0.005, is deleterious for the finding of new discoveries and the progress of science. Given that blanket and variable alpha levels both are problematic, it is sensible to dispense with significance testing altogether. There are alternatives that address study design and sample size much more directly than significance testing does; but none of the statistical tools should be taken as the new magic method giving clear-cut mechanical answers. Inference should not be based on single studies at all, but on cumulative evidence from multiple independent studies. When evaluating the strength of the evidence, we should consider, for example, auxiliary assumptions, the strength of the experimental design, and implications for applications. To boil all this down to a binary decision based on a p-value threshold of 0.05, 0.01, 0.005, or anything else, is not acceptable.