By PENELOPE GREEN

Sheena Iyengar, the S. T. Lee professor of business at Columbia University, was home from work the other day, dressed in a cream-colored twin set and a sparkly gold pencil skirt. She was seated at the head of a long cherry dining table she designed with her husband, Garud Iyengar, a financial engineer who is also a professor at Columbia, in the living room the two had decorated in earthy colors with a mix of furniture found at auction, in India and at a store in downtown Manhattan. There was a consistent style that linked all the objects in the room, including Dr. Iyengar’s outfit.

Yet there was a mystery, too: how had Dr. Iyengar, a social psychologist who firmly believes that taste is an unreliable compass, and who is also blind, navigated the murky landscape of self-expression and made a series of decisions in all sorts of categories - clothes, paint, furniture - that would seem to require both sight and a conviction about taste?

Like most of us, Dr. Iyengar is an expert in none of these areas. She is, however, an expert in choice . In “The Art of Choosing,” her first book, out this month, she presents the biology and the psychology of choice, examining how different cultures construct choice and pondering how we might choose better.

“We’re born with the desire, but we don’t really know how to choose,” she said. “We don’t know what our taste is, and we don’t know what we are seeing. I’m a great believer in the idea of not choosing based on our taste. I could wear makeup today, and one person would say it looks bland, another would say it looks fake, and another might tell me I look really natural. Everyone is convinced their opinion is the truth, and that’s what I struggle against. But doesn’t everyone? What I do is aim for consensus. That’s my rule of how to choose.”

Dr. Iyengar wasn’t kidding. She has built a wardrobe and furnished her apartment by convening a committee of trusted advisers, whose opinions she gathers and then weighs .

“You cannot get to the heart of how things are going to be perceived unless you ask these judges,” she said. “When you’re choosing furniture for your home that’s supposed to express who you are, what you are also saying is you want other people to infer what you want them to infer. What if they see something different? ”

In the mid-’90s, when she was a doctoral student at Stanford, Dr. Iyengar, now 40, conducted her jam study, in which research assistants set out pots of jam on tables in a supermarket - different flavors in groups of 6 and 24 - and offered samples to shoppers. She discovered that many of the shoppers who visited the table with the smaller sampling ended up buying jam along with their other groceries, as compared with a mingy few among those who visited the table with the greater selection. The study made Dr. Iyengar a darling of corporate America and a celebrity in social science circles.

In her book, she described the magic number - seven - at which “more” turns into less.

The number of people in Dr. Iyengar’s committee of experts hovers around five, she said. There are three research assistants: Esther Adzhiashvili, who is Russian and loves color; Kate McPike, who hails from Delaware and “likes J. Crew”; and John Remarek, “who everyone says you can tell has no interest in clothes.”

Sometimes her personal trainer joins, or another friend. Her husband always gets a vote (she sees him as “maverick” in his tastes ? he wanted to paint their family room black ? yet he described himself in an e-mail message to this reporter as conservative, proving his wife’s contention that labels are wildly subjective).

“At first people are nervous,” she said. “Then they loosen up, and knowing their opinions are just one of a group’s and that I don’t always go with their opinions, they get more competitive, which makes them state things in a more pure way.”

It’s been a two-year process, “and we’re still not done,” Dr. Iyengar said. “You have to be choosy about what you choose.”