A physiological marker for false memories

False memories are easily created. Our memories of historical events can be manipulated with doctored photographs; psychiatrists have been known to implant false memories of childhood sexual abuse and Satanic rituals in patients; and false memories are the most likely explanation for claims of alien abduction. All of this profound and wide-ranging implications, but as yet there is no reliable way of determining whether a memory is true or false. Researchers from the University of Giessen in Germany now report that a simple physiological test can distinguish between false memories real ones.

All of the physiological parameters measured are controlled unconsciously by the autonomic nervous system, and reflect functions such as the orienting reflex. The orienting reflex is a response to small changes in the environment, whose strength depends on the intensity, novelty and significance of the new stimulus. Repeated presentation of a stimulus therefore makes it more familiar, leading to a smaller reflex, and to a decrease in the associated responses. On the other hand, any change in the stimulus evokes a reflex that produces larger responses.

Thus, a stimulus that has already been encountered will be more significant than one that has not, because it is more familiar, and this will be reflected in increased skin conductance. The researchers reasoned that falsely recognized items would be less significant than those encountered before, and would therefore be associated with decreased skin conductance. This is exactly what they found

This is the first study to use physiological measurements to investigate false memories, and the findings suggest that basic, involuntary responses can be used to distinguish between false memories and real ones.

The main difference between false memories and lies is awareness: people are unaware that a memory is false, but are fully cognizant of the truth when lying or concealing incriminating information. In some cases, though, people can have implicit knowledge of an event without being consciously aware of it (subception as opposed to deception).

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