IS HUMAN MEMORY RELIABLE?

Is human memory reliable?

Is human memory reliable?

Introduction

Reports from eyewitnesses play an important role in the development and propagation of both religious and paranormal beliefs. People are often ready to believe the personal reports of what others say that they have seen and experienced. Thus, it is important to consider just how reliable people's memory and their testimony can be. Perhaps the most important thing to note is that, even though there is a popular perception of eyewitness testimony being among the most reliable forms of evidence available, the criminal justice system treats such testimony as being among the most fragile and even unreliable available.

Types of Memory

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 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, people describe some basic background on memory and on the types of memory distortions that are common.

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 thought.

Explicit memory stores things that you can consciously verbalize. Explicit memory further subdivides into semantic and autobiographical types. Semantic is memory for facts. For example, you know that George Washington was the first president of the United States but probably don't remember the exact circumstances when you learned that fact. Similarly, you may remember the gist of a conversation that you had a year ago, but don't remember the exact words that were used. Introspectively, semantic memory is more like "knowing" than like recalling. It's not so much that people recall George Washington being the first president as people know that George Washington was ...