A couple decided to go to the movies one night. As she pushed his wheelchair into the theater, an usher rushed up. Ignoring the man, he asked the wife, "Where does he like to sit? What can we do for him?"

She just looked at him. Then the man in the wheelchair spoke up. "You'll have to excuse my wife," he said. "She's deaf."That's an old joke, but it points out one of several strange and very common phenomena. People with "invisible disabilities" are treated normally, while those with obvious disabilities the blind, those in wheelchairs, anyone who "looks disabled" are lumped together into what Debra Mair, director of the Utah Independent Living Center in Salt Lake, calls the "assumption of common disability."

My parents are both blind, and I have grown up with it. I have never understood why many people shout when they speak to Mom and Dad. It seems ironic that people do not recognize deafness when they see it, yet treat those with other disabilities as if they were deaf.

Worse, though, than the belief that speaking in a loud voice will break all disability barriers (or language barriers, for that matter), is what I think of as the "invisible wall." When I go to restaurants with my parents, the waitress commonly directs her questions to me: "What would they like to eat?"

"I'll find out," I reply, turning to my parents. "Mom and Dad, what would you like to eat?"

Marian Schooling-Vessels, a former Ms. Wheelchair America and head of the Maryland Governor's Council on Employment of the Handicapped, said she has encountered the same thing repeatedly.

She flies all over the country as part of her job, and she's getting used to it but she'll never learn to like it, and she will take every opportunity to gently correct the people who do it.

"At the airport," she said during a recent conference for women with disabilities, "the steward asked my companion all sorts of questions about me, all the time treating me like I wasn't there."

Dixie Mitchell, Ms. Wheelchair Utah, thinks that so-called "normal" people are uncomfortable with disabilities, and don't know how to act.

Mitchell's husband is blind, and she laughs about some of things people say to her very well-meaning people, too. When the couple spoke about disabilities recently, one woman commented, "Isn't that nice. He can't see you're in a wheelchair."

I understand why people feel uncomfortable with unfamiliar situations. At the conference, I watched Mair move a chair out of the way with her wheelchair. And as I watched, I wondered if I should offer to help her. Would she like the help? Would she resent it?

I am perfectly comfortable offering assistance to blind people because I've done it all my life. But many people think that makes me an expert on all disabilities. My experience with mobility handicaps is very limited. I just didn't know whether I should offer help.

So I asked Mair if I should ask. She gave me a great rule of thumb. "The best thing to do," she said, "is ask if you can help. But don't be offended if someone says no thanks. You've offered and they've answered. You should both be happy with that."

Disabilities are as varied as the people who have them. Some people welcome assistance, others don't. Just like one woman is offended if a man doesn't open the door for her, and another is offended if he does.

I know a blind man who won't accept help from anyone even when he desperately needs it. My parents sometimes take help they don't need, because they believe it's important that people assist each other in general, and particularly because they want help for themselves and others to be available when it is needed.

As varied as the lives of those with disabilities are, all seem to share one dream: That someday, people will see them as people with disabilities, rather than disabled people. "We are people, first," Mair said.

Occasionally someone gives money to Schooling-Vessels. "I never know what to do with it," she said, "and I sometimes want to tell them that I probably make more than they do. So I say no thanks, and if they insist, I give it to someone who does need it.

"It took me a long time to realize why people did that and to not resent it. But I know they want to help in some way, and that's the only way they can think of."

Giving, even inappropriately, is a sign of caring and reaching out to others, two of the most priceless traits in the world.