Maybe you've never mistaken a TV show for real life. But have you ever been in the middle of introducing one friend to another and then awkwardly and inexplicably forgotten one of their names? Or walked into a room and completely forgotten why you went in there?
Memory is fallible. We've all experienced it one way or another. So why didn't evolution make our brains better at remembering?
It turns out that a quirk of memory that may seem like a "sin" in one context can actually be a virtue. If we remembered everything, our minds would be cluttered with unimportant information. We would recall traumatic and sad events just as sharply as when they happened. It's actually a good thing that memories tend to fade over time.
How else might the so-called "sins of memory" be adaptive? Learn more in the article Memory: sins and virtues, by Daniel Schacter (available for free through PubMed Central).
For as unreliable as our memory tends to be, we often put a lot of faith in it. Sometimes this can lead us into arguments where we are later, embarrassingly, proven wrong. But memory's imperfections can lead to much more serious consequences—like when people are sent to prison for something that they did not do.
Judges and juries tend to believe eyewitness testimony. Yet research has shown that people are incredibly vulnerable to false memories—even when they're planted unintentionally by people who mean well. Research has also shown that the more a person repeats a piece of information, such as who they think they saw committing a crime, the more convinced they become that it is true—even if they were uncertain at first.
The Innocence Project is a non-profit organization dedicated to using DNA evidence to overturn wrongful convictions and to reforming the justice system. According to their website, eyewitness misidentification was a factor in 72% of the first 325 wrongful convictions that they helped to overturn. Importantly, these are just the cases where DNA evidence from the crime was available. Eyewitness misidentification is a factor in many other cases that are much harder to disprove.
Morgan, C.A. & Southwick, S. (2014). Perspective: I believe what I remember, but it may not be true. Neurobiology of Learning and Memory, 112, 101-103. doi:10.1016/j.nlm.2013.12.011
Schacter, D.L. (1999). The seven sins of memory: insights from psychology and cognitive neuroscience. American Psychologist 54, 3, 183-203. doi: 10.1037/0003-066X.54.3.182
Schacter, D.L., Chiao, J.Y. & Mitchell, J.P. (2003). The seven sins of memory: implications for self. Annals of the New York Academy of Sciences, 1001, 226-239. doi: 10.1196/annals.1279.012
The Innocence Project. The causes of wrongful conviction. Accessed 9 February, 2016, from http://www.innocenceproject.org/causes-wrongful-conviction