Our brain uses subconscious mental categories to sort through everyday experiences, a new study has found.
The brain knows it's time to cook when the stove is on, and the food and pots are out. When someone rushes away to calm a crying child, it knows cooking is over and it's time to be a parent. The brain processes and responds to these occurrences as distinct, unrelated events.
But it remains unclear exactly how the brain breaks such experiences into "events," or the related groups that help us mentally organise the day's many situations.
A dominant concept of event-perception known as prediction error says that our brain draws a line between the end of one event and the start of another when things take an unexpected turn (such as a suddenly distraught child).
Researchers led by Princeton University have challenged this idea and suggested that the brain may actually work from subconscious mental categories it creates based on how it considers people, objects and actions are related.
These details are sorted by temporal relationship, which means that the brain recognises that they tend to - or tend not to - pop up near one another at specific times, the researchers reported in the journal Nature Neuroscience.
A series of experiences that usually occur together (temporally related) form an event until a non-temporally related experience occurs and marks the start of a new event.
This dynamic, which the researchers call "shared temporal context," works very much like the object categories our minds use to organise objects, explained lead author Anna Schapiro, a doctoral student in Princeton's Department of Psychology.
"We're providing an account of how you come to treat a sequence of experiences as a coherent, meaningful event," Schapiro said.
"Events are like object categories. We associate robins and canaries because they share many attributes: They can fly, have feathers, and so on. These associations help us build a 'bird' category in our minds. Events are the same, except the attributes that help us form associations are temporal relationships."
Researchers captured brain activity showing that abstract symbols and patterns with no obvious similarity nonetheless excited overlapping groups of neurons when presented to study participants as a related group.
From this, the researchers constructed a computer model that can predict and outline the neural pathways through which people process situations, and can reveal if those situations are considered part of the same event.
The parallels drawn between event details are based on personal experience, Schapiro said. People need to have an existing understanding of the various factors that, when combined, correlate with a single experience.
