How we choose

Human life is a string of seemingly straightforward choices -- getting dressed, picking up a newspaper, and beginning to read this article -- that are surprisingly hard to predict. What sweater will people pull on, which newspaper will they choose, and what will they read first?

As advertisers, financial analysts, and scientists have long known, it's hard to say. Human inconsistency rules.

Now, a budding field called "neuroeconomics" seeks to explain exactly how people make up their minds by using the latest imaging technologies to examine the grayish lump of brain tissue where each decision begins. The researchers, migrs from fields like psychology, neuroscience, and economics, hope to build a theory of human behavior that starts at the level of single nerve cells but can describe the choices individuals make, and even how markets work.

Their goals, ultimately, are to illuminate brain disease, save customers time, money and aggravation, and even improve the national economy by getting consumers and investors to act more rationally.

"But almost everything you can think about that would be helpful has a kind of dark side potential, too," said Colin Camerer, a neuroeconomist at the California Institute of Technology.

Even the field's proponents caution that their work opens the door for manipulation and abuse.

"Most of the studies so far, we're trying to take something we know is probably true and understand it more deeply," Camerer said. "The next step, which we're pretty close to, is to try to change behavior; see if we can do it but not in a big dramatic, brainwashing way."

Researchers state that they seek knowledge for altruistic reasons, with the goal of improving human health, economics, and basic knowledge. But they readily acknowledge that those theories could give unscrupulous advertisers clues about how to best control consumer behavior, or allow anyone with a brain scanner to invade the privacy of one's thoughts.

Major employers, like the government, which already screens job candidates with lie-detector tests, could put new hires in a brain scanner while negotiating salary, and see that, while the candidate might be demanding $40,000 a year, he or she would accept $5,000 less. Graduate-student interviews could be replaced by brain scans that would reveal something more important than essays and test scores -- whether candidates had a lively "curiosity" center.

And while such scenarios may seem like science fiction, they aren't too far-fetched, researchers say. During a recent visit to the Athinoula A. Martinos Center for Biomedical Imaging at the Charlestown Navy Yard, researcher Hans Breiter warned that he could put a person in a brain scanner today, flash 15 images, and then anticipate that person's preferences and choices better than he or she could.

Such information could be extremely valuable to advertisers and politicians eager to understand how people make up their minds or -- better yet -- discover a toggle that switches on impulse buying or makes campaign ads truly persuasive.

Already, neuroeconomists have tried to map what brands and political allegiances look like in the brain. One study of Coke and Pepsi found that, when subjects were told they were drinking "the real thing," brain centers that process memory, emotion, and cognitive control sparked to life, while Pepsi had no similar effect.

Two UCLA researchers put Democrats and Republicans in a scanner and showed them pictures of Ralph Nader, George Bush, and John Kerry -- and found that so-called empathy pathways appeared to light up when seeing a picture of their favorite candidate. When shown candidates they didn't like, their brains were active in the region where higher-level thinking attempts to control emotion.

Brain imaging consulting firms such as the Atlanta-based Bright House and the British Neurosense Limited already offer "neurostrategies" for companies hoping to create literally indelible brands.

While such experiments attract attention, the reality is more primitive. At its core, neuroeconomics is not yet the science of mind reading, but an attempt to patch together three fields, each with its own blind spots.

Economics treats people like rational "particles" that bounce through life trying to maximize money or happiness -- rather than emotional beings who also act in response to social and cultural factors. Psychology doesn't connect behavior to brain biochemistry. And neuroscientists focus on minute areas of the brain without understanding how those areas combine to form a person, said Paul Glimcher, a neuroscientist at New York University who poses economic dilemmas to monkeys and then watches what happens in their brain cells.

Who cares if you find the part of the brain responsible for "laughter while smelling pig urine?" he asked, poking fun at studies he believes are often meaningless. A grand theory of decision-making could cure all three fields of their short-sightedness -- or so researchers hope -- to better explain how the brain drives behavior.

Economists are hoping to use neuroeconomics to revamp theories that don't quite work, to accurately predict interest rates or stock market activity. Evolutionary biologists want to know how our brains are wired to take into account factors like gender, social hierarchies, and competition. Psychologists are eager to figure out the disconnect between people's intentions and their actions. And brain scientists want to understand the neural circuitry implicated in mental illnesses and aging.

One of the great challenges is understanding how the social, emotional, cultural milieu of the real world are coded into the chemistry of the brain.

"People are designed by evolution to make decisions in a social environment," said Michael Platt, an anthropologist-turned-neuroeconomist at Duke University.

Platt's research group at Duke University is trying to understand how social instincts compete with the draw of a reward, like money.

He found that male monkeys will pay in juice to see a picture of a high-ranking monkey, but must be given extra juice to be coaxed into looking at a picture of a monkey on the lowest rung of the social scale. And they will sometimes forgo juice altogether, given the option to see a picture of the hindquarters of a female.

"Even though these monkeys are living in a captive colony, they are carrying around in their heads a program in the brain circuitry that tells the monkeys to maximize their reproductive success or social status," Platt said. He now has data on humans that mirrors the results in monkeys, suggesting that humans, too, calculate a value for things like social status.

Eventually, such simple experiments could give rise to an explanation of how human life, rife with decisions informed by cultural, social, emotional, and rational factors, plays out in the brain and in the wider world -- an explanation that goes far beyond those now offered by economists, psychologists or brain scientists.

"No one is going to prove economics is all wrong," Camerer said. "It's more like sand dunes. The strong winds over time eventually move the sand dunes around."

Carolyn Y. Johnson can be reached at cjohnson@globe.com.