Brain Shows Humans Break Down Events into Smaller Units.

In order to comprehend the continuous stream of cacophonies and visual stimulation that battle for our attention, humans will breakdown activities into smaller, more digestible chunks, a phenomenon that psychologists describe as “event structure perception.”

Event structure perception was originally believed to be confined to our visual system, but new research published in the May issue of Psychological Science, a journal of the Association for Psychological Science, reports that a similar process occurs when reading about everyday events as well.

Nicole Speer and her colleagues at Washington University examined event structure perception by having subjects read narratives about everyday activities while undergoing functional Magnetic Resonance Imaging (fMRI) to measure neural activity. The subjects were then invited back a few days later to reread these same narratives, this time without the fMRI scan.  Instead, they were asked to divide the narrative where they believed one segment of narrative activity ended and another segment began.

Speer, now at the University of Colorado at Boulder, surmised that if changes in neural activity occurred at the same points that the subjects divided the stories, then it could be safe to suggest that humans are physiologically disposed to break down activities into narratives (remember that the same subjects had no idea during the first part of the experiment that they would later be asked to segment the story).

As expected, activity in certain areas of the brain increased at the points that subjects had identified as the beginning or end of a segment, otherwise known as an “event boundary.” Consistent with previous research, such boundaries tended to occur during transitions in the narrative such as changes of location or a shift in the character’s goals. Researchers have hypothesized that readers break down narrated activities into smaller chunks when they are reading stories. However, this is the first study to demonstrate that this process occurs naturally during reading, and to identify some of the brain regions that are involved in this process.

The fact that these results occurred with narratives that described mundane events is particularly important to our understanding of how humans comprehend everyday activity. Speer writes that the findings “provide evidence not only that readers are able to identify the structure of narrated activities, but also that this process of segmenting continuous text into discrete events occurs during normal reading.”

In addition, a subset of the network of brain regions that also responds to event boundaries while subjects view movies of everyday events was activated. Speer believes that “this similarity between processing of visual and narrated activities may be more than mere coincidence, and may reflect the existence of a general network for understanding event structure.” Future research will ultimately address the relationship between the two perception systems, and whether a global mechanism underlies event structure perception.

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