“Time is the thief of memory,” wrote Stephen King in one of his many books. For some people, however, that's not true. These people are gifted with what scientists call "highly superior autobiographical memory" (HSAM), which means that they can remember in vivid detail nearly every day of their life going back to childhood. But new research shows that even these special people are susceptible to forming false memories, sometimes even more so than normal people.

The first study of a person with this special ability, later identified to be Jill Price, was published as recently as 2006. Since then, the list of HSAM individuals in the US has grown to about 30. It includes people like Bob Petrella, who can recall the date he met every one of his friends and acquaintances. Or Brad Williams, who can remember both what he did on any day and what significant world events occurred.

James McGaugh at the University of California Irvine was the author of the 2006 study, and for the past seven years he has been working to understand what makes HSAM individuals so special. A 2012 study showed, for instance, that HSAM individuals have different brain structures. They posses more white matter (neural wiring) in areas linked to autobiographical memory. But because there are so few of them, “[w]e still don’t know enough to be able to draw robust conclusions,” says Martin Conway, a cognitive psychologist at City University London.

Knowing how HSAM people form memories would provide a great leap in our understanding. With graduate student Lawrence Patihis, McGaugh set out to fill that gap. One way to do that was to figure out if HSAM individuals are susceptible to false memories. After all, memories are easy to distort. In a study just published in the PNAS, Patihis finds that HSAM individuals can also be tricked into forming false memories.

Not so perfect

For the study, Patihis recruited 20 out of the 30 known HSAM individuals in the US. They were matched by sex and age with 38 people with normal memory. All of the participants were then given three tests.

In the first test, each participant was shown a series of words that were all supposed to be connected to a “lure word.” If the lure word was “lamp,” they would be shown words like light, table, shade and stand, but not the word lamp. After they had seen the list, they were asked if they saw the word lamp. People with normal memories got the answer wrong seven out of ten times. HSAM individuals also got it wrong just as often.

The second test was more elaborate. It showed a slideshow of photos depicting a crime. After 40 minutes, the subjects were shown words describing the crime, with misinformation sprinkled in them. Twenty minutes later, they were tested to see how many people believed the misinformation to be true. This time HSAM individuals did worse than normal people. They were 73 percent more prone to false memories. “Maybe HSAM individuals form richer memories through absorption of more information and that is why they are also more susceptible to false ones, too,” says Patihis.

Perhaps it's easy to manipulate recent memories. So in the third test, Patihis looked to test long-term memory. All participants were asked to recall the September 11 terrorist attacks. They were then given irrelevant facts about that event, one of which was not true (someone captured the footage of United 93 in Pennsylvania). After 15 minutes, all participants were asked whether they had seen such footage. Like the first test, normal people and HSAM individuals performed almost equally badly on this test.

“This shows that maybe people with superior memories form them just like normal people. Thus, in the process, they are also prone to making the same mistakes,” says Patihis. Equally, there may use a different process of forming superior memories, but one that has same problems as that of the normal process.

There is still contention among experts about whether HSAM individuals are “special.” K. Anders Ericsson of Florida State University says, “Our work has pretty much concluded that differences in memory don’t seem to be the result of innate differences, but more the kinds of skills that are developed.” To which McGaugh says, “You’d have to assume that every day they rehearse it… The probability of these explanations dwindles as you look at the evidence.”

Price had admitted that remembering everything meant bad memories were always around to trouble her. That led researchers to think that such superior memory may come at a cognitive cost of lost abilities or less happier lives. But research since has shown that this is not the case—HSAM individuals tend to have similar lives to normal people. With the latest study, McGaugh has shown one more task where HSAM individuals are normal. They too may be made to believe that as a kid they were lost in a shopping mall, even if that isn’t true.

PNAS, 2013. DOI: 10.1073/pnas.1314373110 (About DOIs).

This article was first published at The Conversation.