Daniel Schacter and Scott Slotnick, at Harvard University, Massachusetts, found that sensory areas of the brain, rather than the regions thought to deal specifically with memory, are more active when people recall information correctly.

The researchers asked volunteers to try to recall whether a particular shape had been in a previously viewed group, while scanning their brains. When people correctly recognised a shape, a visual area called the ventral temporal cortex was more active than when people mistakenly identified a shape that was in fact only similar.

Schacter also found a similar effect with word lists, where auditory regions of the brain became more active during accurate rather than false recognition. "There seems to be an additional feature of a memory that is present for something you have already experienced," says Schacter...