MUCH OF WHAT we do goes on outside the pale of consciousness: whether we adjust our body posture or decide to marry someone, we often have no idea why or how we do the things we do. The Freudian notion that most of our mental life is unconscious is difficult to establish rigorously. Although it seems easy to answer the question “Did you (consciously) see the light turn on?” more than 100 years of research have shown otherwise. The key problem is defining consciousness such that one can measure it independently of the internal state of an individual’s brain while still capturing its subjective character.

One common experimental assessment of consciousness—or awareness of sensation, perception or thought—is based on “confidence.” For instance, a subject has to judge whether a cloud of dots on a computer screen moves to the left or to the right. He then reports how confident he is by assigning a number—for example, 1 to indicate pure guessing, 2 for some hesitation and 3 for complete certainty. This procedure assumes that when the subject has little awareness of the dots’ direction of motion his confidence is low, whereas if he clearly “saw” the motion his confidence is high.

The Money Question

Now a report by Navindra Persaud of the University of Toronto and Peter McLeod and Alan Cowey of the University of Oxford introduces a more objective measure of consciousness: it exploits people’s desire to make money. This method was adapted from economics, where it is used to probe a subject’s belief about an event’s likely outcome. People who know that they have information are willing to bet on it. That is, they are willing to put their money where their mouth is. Think of investing in mutual funds. The more certain you are that high technology will do well over the next year, the more money you will allocate to a technology-sector fund.

Persaud and his colleagues use this kind of wagering to reveal consciousness or lack thereof. In their experiments, subjects do not state their confidence in their awareness directly. Instead they first make a decision regarding whether they have perceived something and then must wager either a small or a large amount of money on their degree of confidence in this decision. If the person’s decision proves correct, she wins this money; otherwise, she loses it. The optimal strategy is to bet high whenever she feels that she is not merely guessing. The experimenters apply this wagering technique to three examples of nonconscious processing.

The first experiment involves patient G.Y., who has “blindsight” from a car accident that damaged areas of his brain involved in visual processing. This condition leaves him with the nonconscious ability to locate a light or report the direction in which a colored bar on a computer screen is moving, although he denies having any visual experience of that bar; he insists that he is simply guessing. G.Y. can indicate the presence or absence of a faint, small grating correctly in 70 percent of all trials, far above chance (50 percent). Yet he fails to convert this superior performance into money when wagering; he places a high bet on only about half (48 percent) of his correct choices. When G.Y. is consciously aware of the stimulus, he wagers high—much as you or I would.

His wagering thus seems to mirror his conscious awareness of the stimulus (that is, his belief that he saw it) rather than his actual (unconscious) detection of the stimulus, suggesting that wagering may provide a means to measure awareness.

The second experiment involves an artificial grammar task in which participants learn a small number of short letter strings. They are then told that the strings obeyed a simple rule (of the kind, for example, that every “x” is followed by an “a”). But they are not told what the rule is. When shown a new string, subjects can more often than not determine correctly whether the new string follows the unknown rule. Yet only rarely can they articulate why they believe a string does or does not obey the rule. The overall rate of correct classification (81 percent) is far better than chance. Yet subjects do not convert performance into money. High wagers follow a correct choice 45 percent of the time and follow a false choice 32 percent of the time. In short, the study participants are usually right about whether the string follows the rule, but they lack enough confidence to bet on it.

Winning Hands

In the final experiment, called the Iowa gambling task, subjects pick the top card from one of four decks. Each card wins or loses the person a certain amount of money. Unbeknownst to the participants, two of the four decks have a net positive yield and two have a negative yield. They must place a low or high wager on the chosen card before it is revealed and lose or win accordingly. In the test, the subjects turn scores of cards over, one by one, each time finding out whether they win or lose. They almost always figure out which decks are winners and start to pull cards mostly from those decks—but they usually turn over at least 30 cards on those decks before they gain the confidence to bet aggressively on the results. That is, subjects only start to make money long after their own behavior should have revealed that they knew which decks were winners.

To explore this hesitation, Persaud and his colleagues used a variant of this experiment in which they queried the subjects every tenth trial regarding everything they knew about the game and the decks. When the subjects thus examined their knowledge of the game, the gap between the onsets of positive deck selection and advantageous betting disappeared, suggesting that the act of introspection alters subjects’ awareness. Examining their knowledge made them more aware of what they knew. This finding indicates that if subjects learn to trust their gut instincts—and bet on knowledge they are not yet aware of—they can do better, a demonstration of the utility of the leitmotif of Western philosophy, “Know thyself.”

The wagering techniques used by Persaud, McLeod and Cowey rely on people’s instinct for reaping a profit. Compared with forcing subjects to become aware of their own consciousness—and in the process perturbing the very phenomenon one wishes to measure—wagering provides a more subtle way to assess awareness. This is an exciting and revealing new way to study awareness and consciousness. From such small steps comes progress in answering the age-old question of how consciousness arises from experience.