Brain Dump: the importance of consensus in conversation

by Arhana Aatresh (’23) | October 7, 2022

Art by Marlena Lisac (’23)

Welcome to Brain Dump! I’m excited for a year of exploring the mysteries and wonders of our brain and how they manifest in our thoughts and actions. 

As high schoolers, we’re familiar with disagreement, which happens in diverse situations, running the gamut from social settings to academic discussions, i.e., which ethnic cuisine for lunch, preferred topic and even slides template for a group project, and more! Our prefrontal cortices only fully develop by age 24, and research shows teenagers tend to be quite stubborn until then. However, we ultimately reach a consensus through conversation. While sometimes painful, it’s key to solving most problems in the world, such as disease diagnosis, police cases, international agreements, and a plethora of crucial problem-solving scenarios.

Dr. Beau Sievers, with Dr. Thalia Wheatley, at Dartmouth College’s Department of Psychological and Brain Sciences, sought insight into how such consensus-building conversation actively changes how our brains function.

In the experiment, the participants watched movie clips with ambiguous narratives, which often imitate realistic situations. During the task, researchers scanned their brains using functional magnetic resonance imaging (fMRI) to monitor their activity; the participants then filled out a survey, where they recorded their thoughts about what the clip was conveying.

Participants then discussed the clips in small groups around a table, with the ultimate goal of reaching a consensus about the plot. After chatting, they recorded the group’s consensus. Afterwards, the participants repeated the first step with additional clips featuring the same characters, and re-recorded their individual beliefs about the narratives. By doing so, the researchers ensured that the only factor impacting the participants’ beliefs was consensus-building conversation.

A surprising 96% of the participants reported that they agreed with their group’s consensus, although agreement varied from group to group. For example, for a scene from Birth (2004), some groups thought that the woman in the movie had previously abandoned her son, the boy in the movie, while others thought they were unrelated. 

Additionally, upon the rewatch of the clips, participants’ recorded beliefs were more aligned with their group mates’ beliefs than they were before the conversation, signaling that the consensus influenced their personal beliefs.

Upon conversation, brain activity in the visual and auditory sensory areas and attention and default mode networks for participants within groups aligned more, including the angular gyrus and medial prefrontal cortex. Their brains were also synchronized upon the clip rewatch. This alignment was measured by the inter-subject correlation (ISC) of blood-oxygen level dependent from fMRI, which analyzes changes in blood flow. As Dr. Sievers states, “consensus-building conversation can cause groups to share a way of seeing the world by aligning their future brain activity.” 

However, just as interpretations varied between groups, brain patterns between groups were also not synchronized.

Dr. Sievers further explains that the study “demonstrates the power of words to shape how our brains process the world.” While its findings reinforce our faith in conversation and the ability to reach common ground, they also speak to how easy it is for people’s views to be buried for the sake of harmony. This trend has serious implications for people whose opinions impact our everyday lives, such as legislators, where valuing consensus over one’s fundamental beliefs may result in dangerous politicians being elected. 

As teenagers, we need to ensure that we’re amplifying the voices of those who can’t express their unique thoughts, and to ensure their beliefs are not compromised. To induce change towards positive behavior at an individual and societal level, we can start by being aware of others’ behavior; for example, be more aware during your next English Socratic seminar. 

Conversation is of paramount importance, and it’s natural and important for us to be able to change our minds, but setting a clear goal at the start ensures that people will not change their beliefs “just because.” We have the power to shape how our own and others’ brains physically process the world, and it is our responsibility to use this for good.

Categories: Column, Science

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