The latest in my ‘Learn Something New Every Day’ series – taken from The Great Courses’ “Trails of Evidence: How Forensic Science Works” (Lecture 28: Human Memory and Eye-witness Accounts)
Brains try to help, but… Our brains don’t capture an event exactly as it happens, they capture an ‘impression’ of an event, including input from all senses. Because our brains file these experiences away into different categories (‘schema’) when we have a new one, our brain rolls out all the old experiences from that same schema (eg: life threatening incidents) to help us process the new one and may even insert information from a previous experience into this experience, changing how we remember the recent event. This means the person is actually remembering information from different events but it seems absolutely real to them.
Collective Memory – One person’s memory can be tainted by someone else in a group situation by ‘adopting’ the memories of another. When in groups, people’s recollection will change subtly.
Unconscious Editing – Studies suggest that a victim of crime may (inadvertently) change the face of the perpetrator as a subconscious defence mechanism. In cases of sexual assault, particularly, victims often try to make the face of an unattractive attacker more attractive, perhaps to cope better with the mental trauma, and can become very distressed when faced with the actual face of their ‘monster’ assailant.
Stress plays a huge part in effective memory. In research testing, people placed in a stressful interrogation situation misidentified the person who had interrogated them face-to-face in a well lit room for forty minutes nearly 70% of the time. IN a second group who were interrogated in a low stress manner, only 12% managed to identify the wrong person.
Weapon Focus Affect – this is a well known phenomenon where a witness focuses on the weapon, not the perpetrator which leads to incorrect or inadequate memory of the crime. Even when they consciously try to remember the witness their ability to recall is dominated by the “O” of that barrel pointing at them.
Studies have shown that people’s memory of an event sharply decreases after just 20 minutes has elapsed.
Why prosecutors should be wary about people who are absolutely certain of what they saw. Generally speaking, the degree of certainty that an eyewitness is inversely proportional to the correctness of their recollections. In other words, people may go to their graves believing a completely incorrect memory.
It pays to be unremarkable Studies have shown that some faces are easier to remember than others. Faces that would be described as distinct (attractive, unattractive, remarkable in some way) are better remembered than a simply typical/average face. You’d remember a bank robber that looks like Brad Pitt or Quasimodo much more readily than one who just looks like every other person there. And you’d probably have better luck describing them, too.
People are always more confident about what they’ve heard than what they’ve seen yet ear-witness testimony (auditory recollections) is even less reliable than sight testimony.
Eyewitness misidentification is the single greatest cause of wrongful convictions in the US (and, statistically, other countries) playing a role in more than 75% of convictions overturned through DNA testing. The US ‘Innocence Project’ has freed 250 people wrongly convicted in the US in the past two decades.