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A vivid memory of a traumatic event, right? Well, not exactly. Piaget goes on: "When I was about fifteen, my parents received a letter from my former nurse saying that she had been converted to the Salvation Army. She wanted to confess her past faults, and in particular to return the watch she had been given on this occasion. She had made up the whole story, faking the scratches. I, therefore, must have heard, as a child, the account of this story, which my parents believed, and projected it into my memory."

Piaget was remembering something he'd been told about, but never experienced. Memory researcher Elizabeth Loftus has experimented extensively in the laboratory with how memories can be changed by things that you are told. Your memories are vulnerable to what she calls "post-event information"--facts, ideas, and suggestions that come along after the event has happened. You can, unknowingly, integrate this information into your memory, modifying what you believe you saw, you heard, you experienced. Over time, you can integrate post-event information with information you gathered at the time of the event in such a way that you can't tell which details came from where, combining all this into one seamless memory.

The information that you integrate can come from something as subtle as a leading question. In laboratory situations, Loftus has documented such memory modifications. After showing a group of college students a film of an automobile accident, she asked a number of questions about the event. Among other questions, one group of students was asked, "About how fast were the cars going when they hit each other?" Another group was asked, "About how fast were the cars going when they smashed into each other?" A third group was not asked about the cars' speed.

The students who were asked about the cars' speed when they "hit" estimated speeds significantly lower than the students who were asked about the cars' speed when they "smashed into" each other. A week later, Loftus asked the students another series of questions about the accident, including "Did you see any broken glass?" The film had shown no broken glass, but the students who had been asked about the cars "smashing into" each other were much more likely to remember broken glass--which makes sense since an accident at a higher speed is more likely to result in broken glass.

With the same sort of questioning, Loftus has led people to believe that they saw a yield sign where they saw a stop sign, to remember a clean-shaven man as having a mustache, to recall straight hair as curly.

Maybe that doesn't seem like such a big deal to you. Sure, the details may be off, but the basic memory itself is still correct. It's not as though it's a false memory--like being a secret agent on Mars, say, or having someone try to kidnap you from your pram.

By Mildred Howard. From the collection of Daniel Schacter.

But Loftus's research doesn't stop there. Working with her students, she has created whole memories, as detailed as Piaget's memory of the attempted kidnapping. One of her students provided his fourteen-year-old brother, Chris, with one-paragraph written descriptions of four childhood events, one of which was false. (The false event was that Chris had been lost in a shopping mall when he was five.) Over the next five days, Chris wrote about whatever details he could remember from all four events, adding details to his "memories."

A few weeks later, Chris was asked to describe each event and rate the clarity of each memory on a scale of one (not clear at all) to eleven (very, very clear). The shopping mall memory got his second-highest rating, number eight. He could describe being lost in detail.

Finally, Chris was told that one of his memories was false. When asked which one he thought it was, he chose one of the real memories. When told that the shopping mall memory was fabricated, he had a hard time believing it.

Other researchers have produced similar results. Dr. Stephen Ceci and his colleagues asked preschool children about things that had happened to them and, in the same conversation, about something that had never happened: for instance, the time they got a finger caught in a mousetrap and had to go to the hospital to get the trap off. Once a week, for ten weeks, the children were asked to think hard about the events and try to imagine them. Finally, the children were asked about the imaginary events.

More than half the children remembered the made-up events, complete with details about how the mousetrap got on their finger and what had happened at the hospital.