Why do we blush and what are the underlying mechanisms of blushing? Research aims to find out

Why do we blush and what are the underlying mechanisms of blushing? Research aims to find out

In a recently published study in theProceedings of the Royal Society B: Biological SciencesA group of researchers examined the neural substrates and mental processes that underlie blushing in response to introspection.

background

Blushing, an involuntary redness of the face associated with self-conscious emotions such as embarrassment and pride, was considered by Darwin to be "the most human of expressions." Nevertheless, its underlying mechanisms remain unclear. Theories vary as to whether blushing is a higher-level cognitive process involving self-reflection or an automatic response to social exposure. Further research is needed to fully understand the specific neural pathways and cognitive processes that contribute to blushing and self-consciousness.

About the study

Sixty-three female adolescents aged 16 to 20 years from Amsterdam participated in the present study, recruited via social media and the University of Amsterdam student pool. Unaware that they would be singing karaoke, participants were only informed about a social task that involved video watching in an MRI (magnetic resonance imaging) scanner. Initial recruitment included a social anxiety symptoms questionnaire inviting those with high or low scores.

Of 63, 49 attended the MRI session; Others were ineligible due to factors such as piercings or intrauterine devices (IUDs). Nine were excluded due to functional (f)MRI data errors, leaving 40 participants (Mage = 19.3 years, SD = 1.10). One participant had missing cheek temperature data and another had self-reported embarrassment data. Participants were compensated with travel expenses and 30 euros or three student loans. The Ethics Review Board of the Faculty of Social and Behavioral Sciences, University of Amsterdam approved the study.

Participants visited the laboratory twice. The first visit was to sing karaoke while being recorded. The second visit involved watching these videos as well as videos of another participant and a professional singer in an MRI scanner while cheek temperature was taken to assess blushing. Behavioral and physiological data were analyzed using mixed effects regression and Bayesian repeated measures analysis of variance (ANOVA). FMRI data were preprocessed using analysis of functional neuroimages (AFNI), where analyzes capture neural substrates associated with cheek temperature changes and task-evoked activity and use between-subject correlations to measure brain activity similarities.

Study results

The study examined the effects of different viewing conditions on blushing and found significant differences in cheek temperature. Mixed effects models showed a notable increase in blushing in the self-viewing condition (watching yourself sing), with cheek temperature being significantly higher compared to the professional views and other viewing conditions.

The self-view condition elicited the highest blushing response (β = 0.022, p = 0.0049), while the professional condition showed a small decrease in temperature and the other condition showed no significant change. Paired tests within the model confirmed that blushing responses were significantly higher in the self condition compared to the professional condition (β = 0.033, p = 0.003). A Bayesian repeated measures ANOVA supported these results, showing strong evidence for the effects of self-state on blushing (BF10 = 17.3), while other conditions remained closer to zero.

Regarding brain activity, task-dependent analyzes showed that observing activities associated with emotional arousal and salience (medial cingulate cortex, anterior insula, and dorsolateral prefrontal cortex) and reduced activity in the default mode regions (posterior cingulate cortex, cortex, cortex, cingulate cortex, reduced activity) were observed. medial prefrontal cortex and inferior parietal lobule). The professional condition primarily activated auditory regions. Study analysis showed that the cheek temperature increase was associated with activity in the neural nucleus and the raphe nucleus, suggesting a neural basis for blushing.

Further analysis showed that participants who blushed more showed greater activity in the cerebellum (lobule V) and left paracentral lobula. Conversely, negative associations were found in the angular gyri and right fusiform. The interaction between blushing and condition showed that the cerebellar response was stronger in the self condition and the left paracentral lobule response was stronger in the self than in the professional condition.

Furthermore, participants who blushed more showed higher inter-subject correlation (ISC) in early visual cortices, indicating the synchronized neural activity that was time-locked to the content of the video.

Conclusions

In summary, to examine the neural correlates of blushing, participants watched videos recorded of themselves singing karaoke while their physiological blushing and brain activity were measured. Blushing levels were higher when participants saw themselves singing compared to others. Those who blushed more showed increased activation in the left paracentral lobe and cerebellum (lobule V) and temporal processing in early visual cortices.

These results suggest that blushing is associated with self-referential processing and activation in brain areas involved in emotional arousal and attention to self-relevant stimuli. This supports the idea that blushing may be triggered by pre-reflective emotional processes rather than mentalization. The study highlights the role of emotional arousal and attentional functioning in blushing and contributes to the understanding of self-consciousness.

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