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Two neuroimaging studies using functional magnetic resonance imaging and electroencephalography showed that people with similar personalities tend to have similar brain responses when viewing naturalistic stimuli. This effect was stronger than that of similarity in gender, ethnicity, or political affiliation. The study was published in Nature Scientific Reports.
Each person perceives the surrounding world in her/his own specific way. One person might be inspired by looking at a piece of art, another would not even notice it. One person might enjoy participating in an activity, another would see it as a hassle.
Researchers have explored the roots of these alignments at the neurological level and found that shared experiences, close relationships, but also gender and cognitive styles affect whether two persons experiences would be aligned or not. People also tend to synchronize their brain activities during social interactions. It happens passively when the neural activity is evoked by a common stimulus (something triggering our senses). But is this passive neural synchronization related to personality traits?
“Given the growing polarization in our world nowadays, being able to understand how to see the world from someone else’s perspective seems like a critical thing. Our interest was in understanding what enables such alignment across various levels: from behavioral and psychological to the systemic and neural,” said study authors Sandra Matz of Columbia Business School and Moran Cerf of Northwestern University.
The researchers devised two neuroimaging studies to answer this question. The goal of their first study was to examine the relationship between personality traits and synchrony of brain activities using functional magnetic resonance imaging (fMRI). They had 66 students watch a one-hour series of 14 short videos spanning a wide range of genres while undergoing fMRI brain imaging. Basic personality traits of the students were assessed using the Ten-Item-Personality-Inventory (TIPI).
The goal of study 2 was to test whether the results from study 1 can be obtained using whole-brain electroencephalography (EEG), but also to examine the roles of an additional set of narrower personality traits (personality sub-facets) in brain response similarity, to study the underlying perceptual mechanisms using eye-tracking and to determine whether similarities in political ideology, gender or ethnicity were related to the level of neural synchronization.
The 303 participants of this study viewed a set of 104 static images on diverse topics. These participants completed a more comprehensive personality inventory (Big Five Inventory -2, BFI-2) compared to the one from the previous study and a eye-tracker recorded their gaze while watching the pictures.
Study 1 showed that higher similarity of brain responses to viewing videos was linked to higher similarities in personality. This finding held across a number of indicators of neural activity used and across different parts of the brain. Higher personality similarity was again associated with higher similarity of brain responses in study 2, although participants watched pictures instead of videos.
This effect remained even after controlling for similarity in gender, ethnicity, age and political ideology.
“The simplest way of summarizing the work is that we learned that individuals’ way of seeing the world is driven by their personality more than other dimensions (i.e. gender, race, age, political ideology, etc.),” Matz and Cerf told PsyPost.
“That is, two people who have similar personalities (i.e., both are neurotic and agreeable) are much more similar to one another in how they process the incoming stimuli than two individuals from the same gender, age, race, etc. An agreeable 50-year-old Republican Black man is more similar (in how you processes incoming natural stimuli) to an agreeable 24 years old Democratic Asian woman than to another 50-year-old disagreeable Republican Black man.”
“We investigate the underlying neural circuits driving this effect and show that this similarity is the outcome of internal evaluation of the content and not a mere focus/attention on different aspects of the incoming stimulus,” the researchers explained.
The same was the case when narrower personality traits (personality sub-facets) were considered, with the exception of the sub-facet called aesthetics (facet of the personality trait Openness to Experience). Eye gaze similarity was not associated with either personality similarity or neural response similarity.
“The fact that personality is so much stronger than other features in driving the similarity is quite striking,” Matz and Cerf said. “The intuition would have been that people are more similar to one another based on their, say, political ideology or race than personality, since identity politics as well as race, gender, or age group (i.e., Millennial versus Boomers) are salient in the media constantly and create the impression that the division by those groups is critical. Learning that personality could overwhelm those segmentation variables is quite unexpected.”
The study highlighted an important link between personality and brain activity. However, researchers note that their “work did not directly test the hypothesis that personality similarity is linked to neural synchrony through a shared interpretation of stimuli,” but inferred about that only indirectly. The study also did not investigate the behavioral consequences of neural synchrony and this should be addressed in future studies.
“The study was tested on a specific set of stimuli that are somewhat natural (still images of relatively low emotional valence),” the researchers said. “It is possible/likely that some content will amplify the identity features (race, gender, political ideology) at a level that will be greater than personality. For example, showing videos that are more emotional and target the very concepts of, say, race identity, are likely to increase the magnitude of that dimension.”
“We believe that those types of stimuli make the majority of the content we are engaged with lately (in mainstream media and on social media) and therefore they amplify the division onto echo-chambers based on identity parameters rather than psychological ones. We did not test that, but suspect that is a big interesting next questions.”
In addition, Matz and Cerf — the authors of “The Psychology of Technology” and “Consumer Neuroscience,” respectively — said that it would be “highly interesting to see how those similarities and neural alignments are formed.”
It would also be “useful to see whether we can use the content to ‘decode’ the personality, using neural signals alone,” they added. “That is, put a headset on a person, have them view the content, and see whether – merely by the level of alignment their brain shows with other people – one can diagnose some of their psychological properties.”
“All of those ideas are open questions that were not addressed but could be a critical next step to truly explain some of the underlying aspects of the work that are still uncharted,” Matz and Cerf said.
The study, “Personality similarity predicts synchronous neural responses in fMRI and EEG data“, was authored by Sandra C. Matz, Ryan Hyon , Elisa C. Baek , Carolyn Parkinson, and Moran Cerf.
