As part of the study, participants watched a series of dots making subtle movements on a screen. They were asked to watch until they had decided which direction the dots were moving, before identifying on a clock when their decision had been made. While this was entirely subjective, by applying a mathematical model and previous research concerning how decisions are linked to individual cells in the brain, the investigators were able to correctly predict the choices made by 4 out of 5 participants.
“The participants in our experiment reported a time they felt they were aware of having reached a decision,” Michael Shadlen of Columbia University told Digital Trends. “It’s the time of a feeling, not an action. How can we, or anyone besides the participant, verify that what they reported to us really corresponds to the time of completion? Well, we know that in the brain, decisions like the one we studied terminate when the neural representation of accumulated evidence reaches a threshold level. When it terminates, it does so in a choice. In fact the mechanism is responsible for the tradeoff between speed and accuracy of the decisions. So we leveraged this knowledge to validate the subjective reports of time by asking whether they could be used to predict that subject’s accuracy.”
The reason the work is interesting is because it helps shed light on the point at which a thought goes from being subconscious to conscious. As Shedlen says, it suggests this might be the point at which information that’s gathered by the brain hits some kind of threshold “tipping point.”
“I am motivated to study decision making because it is a tractable piece of cognition,” Shedlen said. “Studying its normal function tells us what it is about a normal brain that makes us ‘not confused.’ When we understand this at the level of neurons, circuits, proteins, we will be better positioned to remedy disorders of the brain that result in dysfunction of ideation, concentration, attention, authorship, comprehension, and so on.”
Yes, it’s just one more piece of the puzzle, but alongside cutting-edge work being done with brain maps revealing which neurons are linked to behavior, or accurately recreating human faces based on brain signals, it’s helping shed light on the important question of how and why we think the way we do. From medical breakthroughs to smarter AI, that could be useful for all kinds of reasons.
A paper describing the research was published in the journal Current Biology.
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