In that study, she stationed someone at a copy machine in a busy graduate school office. When someone stepped up and began copying, Dr. Langer's plant would come up to the person and interrupt, asking to butt in and make copies. The interruption was allowed fairly often, about 60 percent of the time. But the permission was granted almost 95 percent of the time if the person stepping up to interrupt not only asked, ''May I use the copy machine?'' but added a reason, ''because I'm in a rush.''

That seems to make sense. People heard the reason and decided they were willing to step aside for a moment. What was odd, Dr. Langer found, was that if the interrupter asked, ''Can I use the machine?'' and added a meaningless phrase, ''because I have to make copies,'' the people at the machine also stepped aside nearly 95 percent of the time.

The idea, she said, is that the listener at the copy machine heard a two-part statement: a request and something like a reason. That was all their mental script for such a situation required. They never did reflect on the fact that the interrupter's ''reason'' was not meaningful.

The people at the copy machine only began to listen more carefully to the request and judge the reason for it when those interrupting had a large number of pages to copy. They were asking for a big favor, and in this case, adding ''because I have to make copies'' had no effect. Only when people added that they had to hurry would people step aside.

Her most influential studies were some of the earliest to establish the notion of ''learned helplessness'' in nursing homes. She and a co-author, Dr. Judith Rodin, now president of the University of Pennsylvania, found that giving the elderly residents some control in their lives -- such as when to watch movies, where to visit with relatives, whether and how to raise plants -- they fared better. They felt better, and were more able to handle visitors and tasks in the home. In follow-up studies over the next two years they found those in the group given some control continued to be more active, and in fact, ultimately lived longer.

All this apparently stemmed, she said, from an intervention by experimenters that lasted only a few weeks. ''That so weak a manipulation had any effect suggests how important increased control is for these people, for whom decision-making has been virtually nonexistent,'' she wrote in a paper.

In one of the simplest experiments, she asked elderly patients to put together jigsaw puzzles, and measured their success. One group was simply asked to do it, another given ''encouragement only'' and a third was actively helped by the nursing staff to assemble the puzzles. She found that those who were helped performed most poorly and considered the task difficult, while those who did the work themselves performed better and found the task easier.