Copyright 1997 N.Y. Times News Service
(Mar 4, 1997 01:13 a.m. EST) -- In an experiment with broad implications for human behavior, scientists have shown that people have a covert system in their brains for telling them when decisions are good or bad and that the system, which draws upon emotional memories, is activated long before people are consciously aware that they have decided anything.
Intuition and gut feelings have a firm biological basis, said Dr. Antonio Damasio, the lead author of a paper describing the experiment in the current issue of the journal Science. Damasio, a neuroscientist at the University of Iowa College of Medicine in Iowa City, carried out the research with his wife, Dr. Hanna Damasio and two colleagues, Dr. Antoine Becahra and Dr. Daniel Tranel.
These are the first experiments on humans to show that specific brain regions help lead to anticipation about rewards and punishments, said Dr. Read Montague, a neuroscientist at the Baylor College of Medicine in Houston.
In the experiment, 16 players were each presented with four decks of cards, $2,000 in play money and a simple set of instructions. They were told to turn over cards from all the decks, in any order they liked, and to try to minimize their losses and maximize their winnings. Most cards were worth money (usually $50 or $100), but there were also penalty cards.
Players had no way of predicting when a penalty would arise, no way to calculate with precision the net gain or loss from each deck and no knowledge of how many cards they needed to turn over in order to end the game.
The players did not know that the game had been rigged so two "good decks" produced lower immediate rewards but a higher total payout, Dr. Antonio Damasio said. Two "bad decks" gave the thrill of large earnings but greater total losses.
While people played, their palms were wired to a machine that, like a polygraph, detected changes in the electrical conductance of the skin -- a kind of microsweating that is thought to reflect flickers of emotion that do not reach conscious awareness.
The players were also interrupted occasionally and asked to say what they thought was going on.
Two groups of people played the game -- 10 normal subjects and 6 patients with bilateral damage to a brain region behind the eyeballs involved in making decisions.
Normal subjects soon reached a hunch stage, Dr. Antonio Damasio said. They said things like, "I don't know what's going on here, but there may be some kind of hidden rule or spacing of cards." After turning about 50 cards, most of them reached a conclusion: "Hey, two decks are good, and two are bad."
But their actions anticipated the conclusions they voiced later. At the hunch stage, normal players were already making more selections from the good decks than from the bad decks. And their bodies reflected some unconscious perception. Early in the game, every time they reached for a card in a "bad deck," their palms sweated, as if they already expected excess punishment from the bad decks. "They are playing advantageously before they know what is happening," Damasio added.
A couple of normal players, he said, never reached a point where they voiced a conclusion, the conceptual stage, even though they played correctly, guided by the covert system.
The brain-damaged patients never got to the hunch stage, Damasio said, and none of them experienced microsweating in their palms before turning over cards in the "bad decks." But three out of six of the patients did reach the point at which they consciously knew there were good and bad decks, he said. Despite this knowledge, they continued choosing cards from the bad decks, he said, saying that it was more exciting to play from the risky decks or that one could never tell when the rules might change.
Such self-destructive behavior mirrors what happens to these patients in real life, Damasio said. After their brain injury, they tend to make poor financial and personal decisions and have difficulty with all ethical judgments.
Damasio said he viewed the card game as a metaphor for the game of life. Most important things in life are riddled with uncertainty, including decisions about relationships, jobs, buying a house or a future course of action. While people use facts, logic and pure reasoning to make decisions, these inputs are not enough, he said. Decisions are also influenced by what has happened to a person in previous situations, he added, and he speculated that stored emotional memories came percolating up through a circuit in the prefrontal lobes, the region of the brain involved in decision making.
Most of the time, these emotional memories are covert, Damasio said, but these intuitions help guide decision-making on an unconscious level. If covert memories make it into consciousness, he said, they remain enigmatic but are given a name: gut feelings.