Over at Slate, William Saletan has finished a wonderful series on the distortions and dishonesties of memory. Although our memories always feel true, they're extremely vulnerable to errant suggestions, clever manipulations and the old fashioned needs of storytelling. (The mind, it turns out, cares more about crafting a good narrative than staying close to the truth.) Needless to say, this research has profound implications for everything from eyewitness testimony to talk therapy.
After opening with a clever mass experiment - Slate doctored a few political photos, and then demonstrated that a significant percentage of respondents "remembered" the fictional events - Saletan went on to describe the science behind this sentimental delusions. He focused in large part on the important and influential work of Elizabeth Loftus:
One of the things that makes this research on the fallibility of memory so interesting is that we can now begin to explain the cognitive flaw at a cellular level. In recent years, there's been a lot of research in the reconsolidation of memory, or how our the neural representation of our memories is constantly being altered. (Freud called this process Nachtraglichkeit, or "retroactivity". I write at length about it in the Proust chapter of Proust Was A Neuroscientist.)
It all began with a set of extraordinary experiments done in 2000 by Karim Nader, Glenn Shafe and Joseph LeDoux at NYU. To make a long story short, the scientists demonstrated that the act of remembering changes our memories. Nader, et.al. proved this by conditioning rats to associate a loud noise with a mild, electrical shock. (When it comes to pain, the mind is a quick learner.) As predicted, injecting a chemical that stops new proteins from being created also prevented the rats from creating a fearful memory. Since their brains were unable to connect their context to the electrical shock, the shock was always shocking.
But Nader, Ledoux and Shafe took this simple experiment one step further. First, they made sure that the rats had a strong memory associating the shock with the noise. After letting this memory solidify for up to 45 days, they re-exposed the rats to the scary noise and injected a protein inhibitor into their brain. But what made their experiment different was its timing. Instead of interrupting the process of making a memory, they interrupted the process of remembering a memory, injecting the noxious chemical at the exact moment the rats were recalling what the noise meant. According to the dogma of remembrance, nothing much should have happened. The long-term memory should exist independently of its recall, filed away in one of the brain's protected file-cabinets. After the poison is flushed out of their cells, the rats should remember their fear. The noise should still remind them of the shock.
But this isn't what happened. When Nader, et.al. blocked the rats from remembering their fearful memory, the original memory trace also disappeared. After only a single interruption of the recollection process, their fear was erased. The rats became amnesiacs.
At first glance, this experimental observation seems incongruous. After all, we like to think of our memories as being immutable impressions, somehow separate from the act of remembering them. But they aren't. A memory is only as real as the last time you remembered it. The more you remember something, the less accurate the memory becomes. The larger moral of the experiment is that memory is a ceaseless process, not a repository of inert information. It shows us that every time we remember anything, the neuronal structure of the memory is delicately transformed, or reconsolidated. And that is why it's so easy to convince naive subjects that they met Bugs Bunny at Disneyland.
