Quick: What did you eat for dinner yesterday? What about this past Saturday? What about the first Saturday in February? Or the first Saturday of February 2006?
Correctly recalling a meal from a few days ago doesn’t really point to any sort of remarkable skill. But recalling a meal from a decade and change ago may put you in the company of people with a condition James McGaugh, a psychologist at the University of California, Irvine, calls “highly superior autobiographical memory” (HSAM), defined by the ability to remember everything that happened on every day of your life.
Earlier this month, New Scientist published a story on two new studies from McGaugh and his colleagues about people with HSAM — and his theory that their superior memory may be linked to obsessive-compulsive disorder:
McGaugh and his team believe that their extraordinary powers of memory may be rooted in the habitual rehearsal of their past. People with HSAM often show obsessive behaviours, similar to people with obsessive-compulsive disorder (OCD). Petrella [a man diagnosed with HSAM], for example, is a self-confessed “germophobe” who has to clean his car keys if they touch the ground. Price [one of McGaugh’s research subjects] was obsessive about keeping detailed diaries.
In the first of McGaugh’s studies, published in March in the journal Memory, he and his co-authors administered a variety of cognitive tests — things like pattern recognition and word recall — to 50 people with HSAM, in an attempt to identify the traits that might contribute to their condition. Overall, there wasn’t much of a difference in performance between the HSAM and control groups, suggesting that superior memory isn’t directly linked to superior cognitive ability in any other one specific area.
In the second, published in January in Frontiers in Psychology, 30 people with HSAM were asked to describe everything they had done during each day of the past week, and then to do the same for a week from a year ago, and one from ten years ago. A month later, the researchers had them do the same thing, comparing their answers from the two sessions for consistency. Compared to the control group, the people with HSAM didn’t show any significant advantage when it came to remembering the week that had just passed. When they had to reach further back in time, though, the HSAM participants came up with richer, more consistent memories.
As New Scientist noted, the results of the two studies together imply that people with HSAM aren’t necessarily better at making memories, but they are better at retaining them over time. Maybe, the researchers theorized, those memories are crystallized because people with HSAM obsessively revisit the past — the same way a person with OCD might obsessively wash their hands, for example — which strengthens their memories in the process. (The researchers also noted that the brains of people with HSAM, like those of people with OCD, tend to have larger caudates and putamens, two areas connected to movement and learning.)
But Amitai Abramovitch, a psychologist at Texas State University who studies OCD, is skeptical of the hypothesis, pointing out that past research has actually linked OCD to poorer memory in some areas. People with OCD also tend to have lower confidence in their memories, he says, a pattern that fits with the disorder’s characteristic perfectionism: Ask someone with OCD to recall a specific event, and often, “they’ll say ‘I don’t remember,’ because they don’t want to make a mistake.”
On the other hand, that same fear of mistakes may lead some people with OCD to commit details to memory that other people would gloss over, so they can avoid messing up those details when they recall them down the line.
When the brain stores a memory, “emotionally relevant or prominent events will increase the level of detail,” he says. (You may not be able to tell me where you ate dinner on a random Saturday a few months ago, but you could probably tell me where you were when you learned about the September 11 terrorist attacks.) “Making mistakes has emotional salience. People with OCD will code that very strongly.”
And when they commit details to memory, they’ll typically do it very deliberately — the disorder, Abramovitch says, is defined by purposeful decisions. With OCD, “I don’t just walk in the park. I’m thinking about everything I do,” he says. “I need to step here, I need to be conscious of my actions.” McGaugh’s hypothesis, by contrast, holds that people with HSAM replay their memories almost accidentally, an unconscious process rather than an intentional one.
As a result, Abramovitch believes that people with superior memories likely have OCD-like traits — for example, scoring closer to compulsive on the impulsive-compulsive continuum — but not the full-blown diagnosis, which would likely impede their ability to recall so many things with such ease.
Either way, McGaugh said, more research is needed — as he told New Scientist, “We have all these clues, but we can’t yet say that people with HSAM have this ability because of this or that.” In the meantime, there’s still no definitive answer for why some people can remember the entirety of their lives, while others can’t even remember the last place they put their car keys.