"I suppose it is stupid, but natural selection has evolved all kinds of mechanisms in order to win, and this is one of them," Fisher said.
By natural selection, she means thousands of years of evolution. Good looks are often a sign of health and fertility, so evolution has conditioned us to prefer certain looks.
"Don't forget, it's survival of the fittest, and if you have four children and I have no children, you live on and I die out," she said. "So this game of attraction really matters."
Fisher pointed out that we couldn't help our reaction to beauty. It's just automatic.
"When men take a look at a good-looking woman, all kinds of parts of the brain become active so that they can feel better. They want her," she said.
Steve Jeffes, author of "Appearance Is Everything," agreed.
To confirm a hunch, he questioned jewelers, who told him that very beautiful women who wear diamond rings will almost always wear larger diamonds -- more than one carat -- than less attractive women who also wear diamond rings.
But Fisher offered some hope, thanks to nice clothes, makeup and plastic surgery.
"What's nice about it is that we live in a culture where you can begin to level the playing field. Where both men and women can actually make themselves better looking," she said.
They sure do. It's the basis for the "Extreme Makeover" TV shows. When Heather Waghelstein appeared on the show in 2004, she was a 33-year-old aspiring actress who had difficulty landing roles or a boyfriend.
Among the procedures Waghelstein received from "Makeover" were a chin implant, a face-lift, liposculpting, Lasik eye surgery, tooth bonding and a hair transplant.
She told "20/20" that the makeover had changed her life.
"My relations with the opposite sex definitely changed. I got a lot of attention when I came home," she said. "I would go out to bars with my friends and have drinks bought for me."
Had she ever been bought drinks before her makeover?
"Not at 11 o'clock at night," Waghelstein said. "At 3 o'clock at night, maybe I did, but there's a difference."
So many good things come from good looks -- including privilege.
"Men are more willing to move your furniture if you're a beautiful girl," Fisher said. "They're more willing to donate blood to you. They're more willing to stop on the side of the road and help you change your tire."
"20/20" has run tests that demonstrate that.
We once hired two actresses, one pretty, one kind of plain, loaded their arms with a stack of books, and asked them to drop the books in front of people walking by them in New York's Greenwich Village.
Fewer than half the people who passed helped the plain-looking actress. But when it was the prettier actress' turn, 70 percent of the people nearby pitched in to help.
One man even came back with a shopping bag for the pretty girl's books.
Then we went to Bazookas, a New Jersey sports bar known for having pretty servers.
We made up an actress to look homely and gave her a waitress job. Would she then make less in tips than the other women?
Sure enough, customers gave the homely actress smaller tips. Her tips came to 17 percent of her checks. The other servers averaged 25 percent. People just respond well to good-looking people.
One customer told us, "It's not fair, but I mean, that's the way it is."
Fisher says beauty bias is everywhere. It's called the "halo effect."
"People assume that a person who's very good-looking is doing a better job than in fact they are doing. So they rise up in the company, and they have more status. They have more power," she said.
It's unfair, especially if you're not one of the "beautiful people."
"It's just not a fair world," she said.