Scientists from the University of Amsterdam have discovered that people can form false memories within seconds of events. Work published in the journal PLOS One.
To test the accuracy of short-term memory, the researchers recruited 534 volunteers to participate in a series of four experiments. Each experiment was aimed at memorizing a specific sequence of letters of the Latin alphabet.
Participants had to memorize the letter itself, as well as the position of the symbol – normal or mirror. Sometimes people were shown a second, unrelated series of letters. After giving their answers, they were asked to rate their confidence in their correct guesses from very low to very high.
Participants were wrong about 20% of the time, and the error rate jumped to 30% when asked three seconds after the test. In 37% of cases, participants perceived the letters as normal rather than mirrored. They were also generally sure that the letters in the second (side) string of letters were in the letters to be remembered.
Experience shows that the human brain writes experience based on existing ideas (in this case, what a letter should look like). This allows us to produce more accurate predictions about the world by removing features that do not fit these biases.
“It seems that short-term memory does not always accurately reflect what was just perceived. Instead, memory is formed by what we expect to see,” the scientists explained.