Richard Heitz and Jeffrey Schall of Vanderbilt University found the brain switches into a special mode when pushed to make rapid decisions.
The trade-off between speed and accuracy is a universal aspect of decision making and studied extensively in humans -- the brain uses the same basic method to make both deliberate and rapid decisions.
In order to shorten the decision-making time, the brain simply reduces the cumulative amount of neuronal activity it requires before making a decision. Because the brain must make snap decisions based on less information than it uses for slower decisions, the likelihood that it will make mistakes increases.
In their study, the scientists developed a method for teaching monkeys to switch back and forth between fast and accurate decision making in a task that involved picking out a target from an array of objects presented on a computer screen.
"Our tests are like two different game shows. One -- call it Fast Fury -- is like Jeopardy. You must be first to hit the buzzer to answer a question. Buzzing and answering incorrectly is bad, but being slower means you will never earn a reward," Heitz said. "The second game show -- call it High Stakes Showdown -- allows buzzing in at any time [and] gives you the opportunity to answer a question, but being wrong results in a serious penalty."
The neural activity of the player of Fast Fury jumps up even before the question is read, Heitz said.
"The subjective experience of getting ready that we all experience appears to be reflected in the background activity of neurons in prefrontal cortex," Heitz said.
In comparison, the neural activity drops to extremely low levels during High Stakes Showdown while the player waits to hit the buzzer.
The findings, published in the journal Neuron, suggested identical information presented to the brain is analyzed differently under speed stress than under accuracy stress. These unexpected results are controversial and important because they are at odds with currently accepted mathematical models of decision making, which are being used to understand psychiatric and neurological disorders, Heitz said.