Grey Matters

Memory bugs that cause us to mix up words or confuse the faces of people we do not know very well are probably easy to relate to. If you have not caught yourself making one of these errors, you have likely accused a friend of having done so. Human memory, however, can also fail in a far more spectacular fashion, beyond simply melding or overwriting information. In some cases entirely new memories can be fabricated, apparently from scratch.

Perhaps one of the best documented examples of extreme false memories was a string of cases related to repressed memories reported in the 1980s and early 1990s. The seeds of these false memories were sometimes in the form of dreams, and these seeds were often cultivated into real memories by a therapist or counselor, sometimes over the course of years. The cases often involved women accusing their parents of sexual abuse, resulting in severed family ties, depression, and criminal charges. In one case, a 19-year-old woman, Beth Rutherford, went to her church counselor for help coping with stress. After months of counseling Beth uncovered repressed memories of atrocious acts of sexual abuse by her father. The subsequent accusations eventually led her father to lose his job as a minister, and made it difficult for him to find any other job whatsoever.

As in other such cases, Beth later recanted her memories, in part because she faced hard evidence contradicting her accusations. Among numerous facts that showed that the uncovered events could not have taken place was that she was still a virgin, as revealed by a gynecological exam performed at the suggestion of an attorney. Beth later said, "At the end of 2½ years of therapy, I had come to fully believe that I had been impregnated by my father twice. I remembered that he had performed a coat hanger abortion on me with the first pregnancy and that I performed the second coat hanger abortion on myself."

The recall of events that happened to you is called autobiographical (or episodic) memory, and, along with semantic memory, it is a type of declarative memory. Falsely recalling that your father raped you is an incredibly extreme example of a fabricated autobiographical memory. But how reliable are our memories of what did or did not happen to us in the past? Controlled experiments have revealed that children are particularly susceptible to autobiographical errors. This should not come as a surprise to those of us who are skeptical of our own childhood memories. I have memories of my invisible friend named Cuke when I was five years old, but are they accurate? Are they truly my own? Or were they created as I heard my mother retell stories about me and my imaginary buddy?

This is an extract from Dean Buonomano's Brain Bugs published by W W Norton & Company