In a recent study published in the Proceedings of the Royal Society B: Biological Sciences, a group of researchers investigated the neural substrates and mental processes underlying blushing in response to self-observation.
Study: The blushing brain: neural substrates of cheek temperature increase in response to self-observation. Image Credit: sun ok/Shutterstock.com
Background
Blushing, an involuntary reddening of the face linked to self-conscious emotions like embarrassment and pride, was deemed by Darwin as 'the most human of all expressions.' Despite this, its underlying mechanisms remain unclear. Theories diverge on 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-awareness.
About the study
Sixty-three female adolescents aged 16-20 years from Amsterdam participated in the present study, recruited via social media and the University of Amsterdam's student pool. Unaware they would sing karaoke, participants were informed only of a social task involving video watching in a Magnetic Resonance Imaging (MRI) scanner. Initial recruitment included an online social anxiety symptoms questionnaire, inviting those with high or low scores.
Out of 63, 49 participated in the MRI session; others were ineligible due to factors like piercings or Intrauterine Devices (IUDs). Nine were excluded due to Functional (f) MRI data errors, leaving 40 participants (Mage = 19.3 years, s.d. = 1.10). One participant had missing cheek temperature data, and another had missing self-reported embarrassment data. Participants were compensated with travel expenses and 30 euros or three student credits. The Ethics Review Board of the Faculty of Social and Behavioural Sciences, University of Amsterdam, approved the study.
Participants visited the laboratory twice. The first visit involved singing karaoke while being recorded. The second visit involved watching these videos, plus videos of another participant and a professional singer, in an MRI scanner while cheek temperature was measured to assess blushing. Behavioral and physiological data were analyzed using mixed-effects regression and Bayesian repeated-measures Analysis of Variance (ANOVA). fMRI data were pre-processed using Analysis of Functional NeuroImages (AFNI), with analyses capturing neural substrates associated with cheek temperature changes and task-evoked activity, employing inter-subject correlations to measure brain activity similarities.
Study results
The study examined the effects of different viewing conditions on blushing, finding significant differences in cheek temperature. Mixed-effects models revealed a notable increase in blushing in the Self-viewing condition (watching oneself sing), with cheek temperature significantly higher compared to the Professional-viewing and Other-viewing conditions.
The Self-viewing condition elicited the highest blushing response (β = 0.022, p = 0.0049), while the Professional condition showed a slight 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 findings, showing strong evidence for the Self condition's impact on blushing (BF10 = 17.3), while other conditions remained closer to zero.
In terms of brain activity, task-dependent analyses revealed that watching oneself sing activated regions associated with emotional arousal and salience (mid-cingulate cortex, anterior insula, and dorsolateral prefrontal cortex) and reduced activity in default mode network regions (posterior cingulate cortex, medial prefrontal cortex, and inferior parietal lobule). The Professional condition primarily activated auditory regions. Trial-by-trial analysis showed that cheek temperature increases were linked to activity in cranial nerve nuclei and the raphe nucleus, indicating a neural basis for blushing.
Further analysis revealed that participants who blushed more showed stronger activity in the cerebellum (lobule V) and the left paracentral lobule. Conversely, negative associations were found in the angular gyri and right fusiform. The interaction between blushing and condition indicated that the cerebellum's response was more pronounced in the Self condition, and the left paracentral lobule's response was stronger in the Self than in the Professional condition.
Additionally, participants who blushed more exhibited higher inter-subject correlation (ISC) in early visual cortices, indicating synchronized neural activity time-locked to the video's content.
Conclusions
To summarize, to examine the neural correlates of blushing, participants watched videos that were pre-recorded of themselves singing karaoke while their physiological blushing and brain activity were measured. Blushing was higher when participants saw themselves sing compared to others. Those who blushed more showed increased activation in the left paracentral lobe and cerebellum (lobule V) and more time-locked processing in early visual cortices.
These findings suggest that blushing is associated with self-related 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 mentalizing. The study highlights the role of emotional arousal and attentional engagement in blushing, contributing to the understanding of self-awareness.
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