Nearly all of us are born with what we’d consider less than ideal memories. We’ll struggle to remember where our keys our, draw a blank on that new coworker’s name and sometimes pause much longer than we’d like to remember a detail that should be front of mind. The idealised pinnacle, the photographic (or more accurately the eidetic) memory, always seems like an elusive goal, something you have to be born with rather than achieve. However it seems that our ability to forget might actually come from an evolutionary adaptation, enabling us to remember the pertinent details that helped us survive whilst suppressing those that might otherwise hinder us.
The idea isn’t a new one, having existed in some form since at least 1997, but it’s only recently that researchers have had the tools to study the mechanism in action. You see it’s rather difficult to figure out which memories are being forgotten for adaptive reasons, I.E. to improve the survival of the organism, and which ones are simply forgotten due to other factors. The advent of functional Magnetic Resonance Imaging (fMRI) has allowed researchers to get a better idea of what the brain is doing at any one point, allowing them to set up situations to see what the brain is doing when it’s forgetting something. The results are quite intriguing, demonstrating that at some level forgetting might be an adaptive mechanism.
Back in 2007 researchers at Stanford University investigated the prospect that adaptive forgetting was potentially a mechanism for reducing the amount of brain power required to select the right memories for a particular situation. The hypothesis goes that remembering is an act of selecting a specific memory for a goal related activity. Forgetting then functions as an optimization mechanism, allowing the brain to more easily select the right memories by suppressing competing memories that might not be optimal. The research supported this notion, showing decreased activity in anterior cingulated cortex which is activated when people are weighing choices (like figuring out which memory is relevant).
More recent research into this phenomena, conducted by researchers at various institutes at the University of Birmingham and various institutes in Cambridge, focused on finding out if the active recollection of a specific memory hindered the remembering of others. Essentially this means that the act of remembering a specific memory would come at the cost of other, competing memories which in turn would lead to them being forgotten. They did this by getting subjects to view 144 picture and word associations and were then trained to remember 72 of them (whilst they were inside a fMRI machine). They were then given another set of associations for each word which would serve as the “competitive” memory for the first.
The results showed some interesting findings, some which may sound obvious on first glance. Attempting to recall the second word association led to a detriment in the subject’s ability to recall the first. That might not sound groundbreaking to start off with but subsequent testing showed a progressive detriment to the recollection of competing memories, demonstrating they were being actively repressed. Further to this the researchers found that their subject’s brain activity was lower for trained images than ones that weren’t part of the initial training set, an indication that these memories were being actively suppressed. There was also evidence to suggest that the trained memories showed the most average forgetting as well as increased activity in a region of the brain known to be associated with adaptive forgetting.
Whilst this research might not give you any insight into how to improve your memory it does give us a rare look into how our brain functions and why certain it behaves in ways we believe to be sub-optimal. Potentially in the future there could be treatments available to suppress that mechanism however what ramifications that might have on actual cognition is anyone’s guess. Needless to say though it’s incredibly interesting to find out why our brains do the things we do, even if we wished they did the exact opposite most of the time.