Keynote Series: Emily Finn — Exploring individual differences in how we experience the same thing
If you have talked to someone about a movie both of you have watched before, you may have noticed how different their experience is to yours. Beyond just liking or hating the movie, people may remember the same movie differently based on their past experiences, current mental states, interests, etc. Each of our experiences is unique.
There is a growing interest among neuroscientists in studying these individual differences under more naturalistic conditions, such as watching movies, rather than just finding the average (normative) brain activity patterns or studying subjects at rest in an MRI scanner. Dr. Emily Finn and her research team are a part of this movement, using neuroimaging analyses to explore how and why our subjective experiences can be so different.
Social or non-social interaction?
We have a penchant for quickly finding social information around us, sometimes even too much: for example, seeing faces on inanimate objects—a phenomenon called pareidolia. Using short (20 sec) animations of simple geometric shapes interacting, Rekha Varrier and Dr. Finn studied individual differences in whether we perceive an animated interaction as social or non-social.
In similar past studies, scientists typically used their own social and non-social labels to find brain activity induced by each interaction and treated discrepancies in subjects' labels as errors. Varrier and Finn allowed subjects to label interactions as "social", "non-social", or “unsure” then analyzed these subjective labels. Doing so revealed a fascinating bias: subjects were more inclined to label an animation intended to be non-social as "social" than vice versa and social animations got less "unsure" responses. This bias was stronger among those with internalizing traits like loneliness and anxiety.
In addition, they analyzed brain activity captured through functional MRI and found that several brain regions (mostly temporal, occipital, subcortical) showed higher activity while viewing animations labeled "social" than either "unsure" or "non-social". This difference started early (within 2 sec) for most regions, including early visual processing regions. This suggests that our brains may have a separate processing pathway for social perception, like a priority lane.
Neural event segmentation
Event segmentation—the automatic process of splitting an experience into events—is an important step in how we convert them into memories, and previous research has shown that this process can be different depending on various factors like age, cognitive abilities, and psychiatric disorders. Using a recently developed algorithm that uses machine learning (hidden Markov models) to identify brain state changes, Clara Sava-Segal, Dr. Finn, and a team of researchers studied individual differences in how our brains do this process (neural event segmentation).
Subjects watched 4 short movies made by independent filmmakers while being scanned in an MRI. When the researchers applied neural event segmentation to regions across the whole brain separately, they found that brain regions that come later in the information processing pathway (association regions) held less neural events while earlier regions (sensory regions) held more. However, there were more individual differences in neural event boundaries for later regions, perhaps due to an increase in complexity.
Three movies had social content involving people while one only involved non-social objects (Rube Goldberg machine). After watching the movies, subjects were asked to talk about the movie for 3 minutes. Using another machine learning method (Universal Sentence Encoder), researchers measured similarity between each pair of subjects' responses and compared that to the alignment between their neural events. Interestingly, subjects who had more similar interpretations also showed more alignment in neural events. For movies with social content, this effect was strongest in brain regions involved in complex narrative processing (e.g. angular gyrus, superior temporal sulcus, precuneus) while for the non-social movie, it was strongest in motor and attention regions.
Together, these results show that differences in how our brains split a story into events may partly explain why we can have different memories of the same movie.
Furthermore, these studies demonstrate how useful subjective experiences and individual differences can be in neuroscientific studies. If you’d like to know more about Dr. Finn and her research, check out our interview with her here and her upcoming keynote presentation at OHBM 2024!
Sava-Segal, C., Richards, C., Leung, M., & Finn, E. S. (2023). Individual differences in neural event segmentation of continuous experiences. Cerebral Cortex, 33(13), 8164–8178. https://doi.org/10.1093/cercor/bhad106
Varrier, R. S., & Finn, E. S. (2022). Seeing Social: A Neural Signature for Conscious Perception of Social Interactions. Journal of Neuroscience, 42(49), 9211–9226. https://doi.org/10.1523/JNEUROSCI.0859-22.2022
