The Undoing Project: A Friendship that Changed the World(38)

The eye might offer a window into the mind. In Blum’s hypnosis lab, with a psychologist named Jackson Beatty, whom he’d poached from Blum, Danny set out to investigate how the pupil responded when people were asked to perform various tasks that required mental effort: remember strings of digits, or distinguish sounds of different pitches. They were seeking to understand not whether the eye played tricks on the mind, but if the mind also played tricks on the eye. Or, as they put it, how “intense mental activity hinders perception.” They found that it wasn’t just emotional arousal that altered the size of the pupil: Mental effort had the same effect. There was, quite possibly, as they put it, “an antagonism between thinking and perceiving.”



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From Michigan, Danny planned to return to a tenured job at Hebrew University. When the university delayed its decision on whether to give him tenure, he refused to return. “I was very angry,” he said. “I called and said, ‘I’m not coming back.’” Instead, in the fall of 1966, he went to Harvard. (Three years at Berkeley had persuaded him that he was smart enough to play in the big leagues.) There he heard a talk, given by a young British psychologist named Anne Treisman, that sent him in yet another direction.

In the early 1960s, Treisman had picked up where the work of fellow Brits Colin Cherry and Donald Broadbent had left off. Cherry, a cognitive scientist, had identified what became known as the “cocktail party effect.” The cocktail party effect was the ability of people to filter a lot of noise for the sounds they wished to hear—as they did when they listened to someone at a cocktail party. It was in those days a practical problem because of the design of air traffic control towers. In the early control towers, the voices of all the pilots who needed guidance were broadcast through loudspeakers. Air traffic controllers had to filter the voices to identify the relevant airplane. It was just assumed that they could ignore the voices that they needed to ignore in order to focus on the voice that required their attention.

Together with another British colleague, Neville Moray, Treisman set out to see just how selectively people listened when they listened selectively. “Nobody had done or was doing any research in the field of selective listening,” she wrote in her memoir, “so we had it more or less to ourselves.” She and Moray had put people in headphones attached to a two-channel tape recorder and piped two different passages of prose simultaneously into separate ears. Treisman asked the subjects to repeat back to her, as they listened, one of the passages. Afterward, she asked them what they had picked up from the passage they had supposedly ignored. It turned out that they hadn’t entirely ignored it. Some words and phrases got through to the mind, even if they hadn’t been invited. For instance, if their name was in the passage that they were assigned to ignore, people would often hear it.

This surprised Treisman, along with the few other people then paying attention to attention. “I thought at the time that attention was a complete filtering,” said Treisman, “but it turns out that some kind of monitoring goes on. The question I had was, how do we do this? When, and how, does the content get through?” In her Harvard talk, Treisman proposed that people possessed, not an on-off switch that enabled them to pay attention to whatever they intended to pay attention to, but a more subtle mechanism that selectively weakened, rather than entirely blocked, background noise. That background noise might get through was, of course, not the happiest news for passengers in airplanes circling the control tower. But it was interesting.

Anne Treisman was on a flying visit to Harvard, where the demand to hear what she had to say was so great that her talk had to be moved to a big public lecture hall off campus. Danny left the talk filled with new enthusiasm. He asked to be deputized to look after Treisman and her traveling party—which included her mother, her husband, and their two small children. He gave them a tour of Harvard. “He was very eager to impress,” said Treisman, “and so I let myself be impressed.” It would be years before Danny and Anne left their marriages and married each other, but it took no time at all for Danny to engage Treisman’s ideas.

In the fall of 1967 Danny had gotten over his feelings of being slighted and returned to Hebrew University, with the promise of tenure and an entirely new research program. It was now possible, with double-channel tape recorders, to measure how well people divided their attention, or switched their attention from one thing to another. It stood to reason that some people might be better at it than others, and that the ability might offer an advantage in certain lines of work. With this in mind Danny went to England, at the invitation of the Cambridge Applied Psychology Unit, to test professional soccer players. He thought that there might be a difference in the attention-switching abilities of players in the first (premier) league and players in the fourth league. He took the train from Cambridge to Arsenal—home to a top-division soccer team—with his heavy dual-track tape recorder beside him. He put the headphones on the players and tested their ability to switch from the message playing in one ear to the message playing in the other, and found . . . nothing. Or, at least, no obvious difference between them and the players in the lower-ranked league. A talent for playing soccer didn’t require any special ability to switch attention.

“Then I thought, this could be critical in pilots,” he recalled. He knew, from working with flight instructors, that the cadets training to fly fighter jets sometimes failed because they either couldn’t divide their attention between tasks or were slow to pick up on seemingly unimportant but actually critical background signals. He returned to Israel and tested cadets who were training to fly jets for the Air Force. This time he found what he was looking for: The successful fighter pilots were better able to switch attention than the unsuccessful ones, and both were better at it than Israeli bus drivers. Eventually one of Danny’s students discovered that you could predict, from how efficiently they switched channels, which Israeli bus drivers were more likely to have accidents.