November 8, 2012
The Brain Switches Into Special Mode For Rapid Decision Making
Alan McStravick for redOrbit.com - Your Universe Online
Two similar scenarios, but for the timing involved, require different parts of your brain to help you make a decision. Let´s say you are driving on the freeway when the car in front of you blows a tire. You have only milliseconds to process the situation, make your decision and act. Do you slam on your brakes or pull out of the lane suddenly? Either decision could be right or wrong. Scenario 2 has you driving down the same freeway. You see, far ahead of you some commotion from a car that has blown a tire. You have time and distance to decelerate and move to a lane away from the distress.A new research study, conducted by Research Assistant Professor Richard Heitz and Jeffrey Schall who is the Ingram Professor of Neuroscience, at Vanderbilt University, has found that in situations like Scenario 1 above, our brain will actually switch into a special mode that is responsible for making rapid decisions. Their study was published this week in the journal Neuron.
"This is a question that is very basic to our experience as human beings, and something that we encounter on a daily basis," Heitz, who designed and carried out the study, said. "If we can understand how our brain changes when we are pushed to respond faster, we have gone a long way toward understanding the decision-making process in general."
There is an important sacrifice to recognize when making knee-jerk reactions, however. A speedy decision is not always an accurate decision. There have been several studies of human decision making. Numerous behavioral and brain-mapping studies have shown that both deliberate and rapid decisions utilize the same basic methods in the brain. In a higher-stress, higher-pressure situation that requires a more rapid decision, the brain simply reduces the cumulative amount of neuronal activity it requires before making a decision. Making a decision based on a much more limited subset of information than the brain would have for slower decisions, the overall likelihood that it will make a mistake increases.
Researchers were at a full-stop, it seemed, in the study of decision making. They were limited in advancing study because, while humans can be easily prompted between quick and deliberate decision making, there is no safe way to study the individual neurons in the brain and their relation to the decision making process. On the other hand, we can study those neurons directly in monkeys, but they can´t be easily prompted to discern between the speedy and slow decision making processes. Well, that is until now.
The researchers were able to develop a method for teaching the monkeys to switch back and forth between fast and accurate decision making. This method utilized a task that involved the test monkey picking out a target from an array of objects presented on a computer screen. The monkeys were taught to value accuracy and were rewarded for correct responses. Another test group was trained that some mistakes were okay, as long as their answers were fast. Once the monkeys were trained, the researchers were able to monitor the signals that were sent from single neurons in the monkey´s prefrontal cortex. The prefrontal cortex is the area of the brain that is dedicated to higher cognition.
"Our tests are like two different game shows. One — call it Fast Fury — is like Jeopardy. In order to answer a question you must be the first to hit the buzzer. Buzzing in and answering incorrectly is bad, but being slower than the other contestant means you will never earn a reward," Heitz said. "That is much different than the second game show — call it High Stakes Showdown — where buzzing in at any time gives you the opportunity to answer a question, but being wrong results in a serious penalty."
"The first thing you see is that 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." In comparison, the neural activity drops to extremely low levels during High Stakes Showdown while the player waits to hit the buzzer.
This picture differs substantially with the standing theory that the brain uses the same process for all types of decisions. "Our second observation, in particular, was really startling," Schall said. "It really flies in the face of what we thought we knew about decision-making."
Using the researcher´s game show example, what happens when contestants in Fast Fury and High Stakes Showdown are given identical questions? According to the team, the activity of the prefrontal cortex neurons will increase while the observers are deciding how to respond. Their new data suggests, however, that this activity is amplified during the Fast Fury example and suppressed during High Stakes Showdown.
"What this means is that identical information presented to the brain is analyzed differently under speed stress than under accuracy stress," Schall said.
There will be, no doubt, much controversy in the scientific community due to these unexpected results. The team and their research outcome are at odds with currently accepted mathematical models of decision making. The current models are being used to understand psychiatric and neurological disorders. Heitz and Schall have shown how these current models can be modified to make them consistent with the new results. This would help, for example, people with certain types of brain damage who seem to have gotten stuck in a hasty, impulsive mode for deciding. The new research could help provide some indication for how and why this is happening mechanically in the brain.
Should we always strive to make deliberate decisions to eliminate errors in our thinking processes? According to Schall, ““¦there are many situations in life when the cost of not acting is higher than making an error in judgment. For example, if the decision is whether or not to shut down a nuclear reactor in the presence of a potential meltdown, I'd prefer haste."