Eyewitness Testimony
Eyewitness Memory is Unreliable
Marc Green
Introduction
Eyewitness identifications greatly sway both police and juries. As the Thomson example illustrates, an eyewitness identification can even outweigh a strong alibi supported by other testimony. This is sometimes unfortunate because eyewitness memory is highly fallible. Memory errors fall into two classes: people can 1) either completely fail to recall an event or 2) have an inaccurate recollection. People have very different attitudes about the two types of failure. Most people understand that total memory failures are common. They can introspect about occasions when they have been unable to recall an event, so failures by other people are hardly surprising. In contrast, people are overly optimistic about the accuracy of their retrieved memories, probably because most errors have little practical consequence and go unnoticed. Given the confidence in their own memory accuracy, people have too much faith in the accuracy of eyewitnesses. Memory has a multitude of quirks and inaccuracies that creep into its everyday operation. Here, I describe some basic background on memory and on the types of memory distortions that are common.
Types of Memory
It is more accurate to speak of human memories rather than of human memory, since people have several distinctly different types. The basic division is among sensory, short-term and long-term memories. Each of these memories further consists of subsystems. There is a separate sensory memory for each sense, iconic (visual), echoic (auditory), etc. Some also distinguish a "working memory" consisting of separate executive, phonological loop and visuo-spatial subsystems.
Most matters involving eyewitness testimony depend on accuracy of long-term memory, which has at least two subsystems, implicit and explicit memory. Implicit memory stores things that you don 't consciously know, like how to peddle a bike. You just get on the thing and start peddling without conscious
Marc Green
Introduction
Eyewitness identifications greatly sway both police and juries. As the Thomson example illustrates, an eyewitness identification can even outweigh a strong alibi supported by other testimony. This is sometimes unfortunate because eyewitness memory is highly fallible. Memory errors fall into two classes: people can 1) either completely fail to recall an event or 2) have an inaccurate recollection. People have very different attitudes about the two types of failure. Most people understand that total memory failures are common. They can introspect about occasions when they have been unable to recall an event, so failures by other people are hardly surprising. In contrast, people are overly optimistic about the accuracy of their retrieved memories, probably because most errors have little practical consequence and go unnoticed. Given the confidence in their own memory accuracy, people have too much faith in the accuracy of eyewitnesses. Memory has a multitude of quirks and inaccuracies that creep into its everyday operation. Here, I describe some basic background on memory and on the types of memory distortions that are common.
Types of Memory
It is more accurate to speak of human memories rather than of human memory, since people have several distinctly different types. The basic division is among sensory, short-term and long-term memories. Each of these memories further consists of subsystems. There is a separate sensory memory for each sense, iconic (visual), echoic (auditory), etc. Some also distinguish a "working memory" consisting of separate executive, phonological loop and visuo-spatial subsystems.
Most matters involving eyewitness testimony depend on accuracy of long-term memory, which has at least two subsystems, implicit and explicit memory. Implicit memory stores things that you don 't consciously know, like how to peddle a bike. You just get on the thing and start peddling without conscious
References: Baddeley, A. (2004). Your Memory: A User 's Guide. Richmond Hill, Canada: Firefly Books. Norretranders, T., J. (1999). The User Illusion: Cutting Consciousness Down To Size, 186-87. New York: Penguin Books.