How Primate Neurons Turn Flickering Dots Into a Decision
Much of what researchers know about how a brain makes decisions comes from monkeys watching dots. In the random-dot-motion task, a cloud of flickering specks drifts weakly in one direction while the subject tries to determine whether, and in which direction, it is moving.
In the primate neocortex, neurons gather visual evidence over time; their firing rates climb until they cross a threshold, and the animal commits to a decision. Avian brains have no neocortex, so it was not obvious how birds made similar decisions.
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The threshold is a useful picture of a decision: not a single flash of certainty, but evidence piling up until a verdict is forced.
The bird problem is the interesting crack in that picture. If a similar decision can be made without a neocortex, the threshold may describe one architecture's implementation, not decision-making itself.