Another possible cause of forgetting resides in the concept of repression, which refers to forgetting an unpleasant event or piece of information due to its threatening quality. The idea of repression was introduced in the late 19th century by Austrian physician Sigmund Freud, the founder of psychoanalysis. According to Freudian theory, people banish unpleasant events into their unconscious mind. However, repressed memories may continue to unconsciously influence people’s attitudes and behaviors and may result in unpleasant side effects, such as unusual physical symptoms and slips of speech. A simple example of repression might be forgetting a dentist appointment or some other unpleasant daily activity. Some theorists believe that it is possible to forget entire episodes of the past such as being sexually abused as a child due to repression. The concept of repression is complicated and difficult to study scientifically. Most evidence exists in the form of case studies that are usually open to multiple interpretations. For this reason, many memory researchers are skeptical of repression as an explanation of forgetting, although this verdict is by no means unanimous. For further information on repressed memories, see the sidebar “Recovered Memories and False Memories” that accompanies this article.
Biological Basis Of Memory
One of the most exciting topics of scientific investigation lies in cognitive neuroscience: How do physical processes in the brain give rise to our psychological experiences? In particular, a great deal of research is trying to uncover the biological basis of learning and memory. How does the brain code experience so that it can be later remembered? Where do memory processes occur in the brain?
In the early and mid-1900s, psychologists engaged in the “search for the engram.” They used the term engram to refer to the physical change in the nervous system that occurs as a result of experience. (Today most psychologists use the term memory trace to describe the same thing.) The researchers hoped to find some particular location in the brain where memories were stored. This early work, conducted mostly with animals, failed to find a specific locus of memory in the brain. For example, American psychologist Karl Lashley trained rats to solve a maze, then surgically removed various parts of the rats’ brains. No matter what part of the brain he removed, the rats always retained at least some ability to solve the maze. From such research, psychologists concluded that memory is distributed across the brain, not localized in one place.