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Filling in the Gaps

Study shows memories can be imagined

FRIDAY, July 6, 2001 (HealthDayNews) -- How often have you seen something after it happened and assumed you knew what caused it to happen?

To make sense of our world, we often trick ourselves into thinking we actually remember why something happened, a new study shows.

For instance, if we see a boy in a chair crash to the floor, we assume he leaned back too far and lost his balance. Later we "remember" seeing the boy leaning back too far.

Researchers found that when they showed students the effect of something without its cause, many later believed they remembered the cause, demonstrating that memory is more malleable than we think.

"People are eager to try to attribute things in the world to a cause. We have a natural tendency to contribute effect to a probable cause. People want to have a coherent idea of what they remember in the world. They want to connect what they see to what they know," says study co-author Mark Tippens Reinitz.

The study was designed to find out whether that proclivity would lead to memory mistakes. The findings appear in the July issue of Journal of Experimental Psychology: Learning, Memory and Cognition.

Tippens Reinitz says he and colleague Sharon Hannigan decided to look at this phenomenon because the whole area of memory illusion has exploded in recent years.

"This was just an area that was wide open. It seemed intriguing from the outset," he says.

The study included three experiments with 144 Boston University undergraduates. The researchers set up slides of four different scenarios: eating at a restaurant; shopping for groceries, getting up in the morning, and attending a lecture. In the first experiment, the students sat in a dark room and viewed eight scripts from each of the four scenarios. Only half of the eight scripts followed stereotypical cause-effect patterns. Afterwards, there students took a 20-minute multiple-choice test.

The students then were shown 16 scenes and asked whether they had seen them during the first part of the experiment. Most students remembered more of the scenes that followed stereotypical cause-effect patterns.

In the second experiment, researchers showed the students one part of a two-part scene. For example, students would see a woman pulling an orange from the bottom of a stack of fruit, or they would see oranges toppling to the floor. In most cases, the students would believe they had seen what caused the oranges to fall even though they had not. However, if they saw only the woman plucking the oranges from the stack, they did not assume the oranges would fall.

The longer researchers waited to ask students to remember what they had seen, the greater the tendency to fill in the gaps in sequences and for the students to say they had seen things they had not.

Tippens Reinitz explains the phenomenon this way: If you tell someone you went out to dinner the night before, and he asks you if you ordered food, you'd look at him as if he were an idiot. That's because we assume certain causes create certain effects.

"It's an adaptive tendency people have to generalize," he says. "People see the woman picking up oranges on the floor. They think they were dropped. They don't remember the cause was self-generated. That's what we think is happening here."

Memory researcher Linda Henkel says the study points to the potency of the human need to make sense of things.

"The one thing this study really does is it drives home this natural inference process we do," says Henkel. "It could be the case that we constantly make inferences about things. It's not just the case that memory randomly draws distortions. I think our experiences are a lot more piecemeal than we realize. We take all these separate pieces and put it all together as one memory."

Tippens Reinitz says that's not necessarily a bad thing.

"Memory works pretty good. What produces errors might be an adaptive tendency. When we make causal inferences, they are more likely than not to be correct. In general, it serves us well," he says.

What To Do

To read more about false memories, visit the False Memory Syndrome Foundation.

Check this research on memory illusions.

Read about how false memories hold up better than real ones as we age.

Try this memory test using pennies.

SOURCES: Interviews with Mark Tippens Reinitz, assistant professor, psychology, University of Puget Sound, Tacoma, Wash.; Linda Henkel, assistant professor, psychology, University of North Florida, Jacksonville, Fla.; July 2001 Journal of Experimental Psychology: Learning, Memory, and Cognition
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