(head lines)

8 SCIENTIFIC AMERICAN MIND November/December 2009

GA

BE

PA

LM

ER

Co

rbis

VA

ND

A G

RIG

OR

OV

IC i

Sto

ck

ph

oto

What’s this guy thinking? Does he know what I know? Most of us devel-op the ability to make inferences about what other people might be thinking, the hallmark of “theory of mind,” at age four. Scientists have long known that the acquisition of language plays a role in this process, but so far it had been unclear whether social experience could substitute for it. A new study suggests it cannot.

Jennie Pyers of Wellesley College and her colleagues studied deaf adults in Nicaragua. Some of the participants had learned an early, rudimentary form of Nicaraguan sign language (NSL), whereas others were fl uent in a more sophisticated form of NSL that in-cluded mental state terms, such as “know” and “think.” Pyers and her team had all signers undergo a so-called false-belief test in which signers looked at a sequence of pictures showing two boys playing in a room and storing a toy underneath a bed. After one of the boys leaves the room, the other moves the toy to a different location. Study participants then had to choose between two pictures to complete the series: the fi rst showed the returning boy looking for the toy in its original location on reentering the

room, and the second showed him looking in its new location.

Those Nicaraguans with complex sign language skills were more likely to choose the fi rst picture—indicating an understanding of false belief—than were those with less developed language skills. Moreover, after a two-year period during which early signers

improved their NSL knowledge, they performed better at the false-belief task.

The fi ndings support the hypothesis that although an implicit understand-ing of other people’s knowledge and belief states develops early in life, ad-vanced language is needed “to unlock the ability to productively use it,” Pyers says. —Nicole Branan

>> LEARNING

Why Success Breeds Success

The brain may not learn from its mistakes after all

Have you ever bowled a string of strikes that seems like it came out of nowhere? There might be more to such streaks than pure luck, according to a study that offers new clues as to how the brain learns from posi-tive and negative experiences.

Training monkeys on a two-choice visual task, researchers found that the animals’ brains kept track of recent successes and failures. A correct answer had impressive effects: it improved neural processing and sent the monkeys’ performance soaring in the next trial. But if a monkey made a mistake in one trial, even after mastering the task, it performed around chance level in the next trial—

in other words, it was thrown off by mistakes instead of learning from them.

“Success has a much greater infl uence on the brain than failure,” says Massachusetts Institute of Technology neuroscientist Earl Miller, who led the research. He believes the fi ndings apply to many aspects of daily life in which failures are left unpunished but achieve ments are rewarded in one way or another—such as when your teammates cheer your strikes at the bowling lane. The pleasurable feeling that comes with the successes is brought about by a surge in the neurotransmitter dopamine. By telling brain cells when they have struck gold, the chemical apparently signals them to keep doing whatever they did that led to success.

As for failures, Miller says, we might do well to pay more attention to them, consciously encouraging our brain to learn a little more from failure than it would by default.

—Frederik Joelving

>> COMMUNICATION

Reading MindsAdvanced language skills may be essential to predicting others’ thoughts