Much has been written on the wonders of human memory: its astounding feats of recall, the way memories shape our identities and are shaped by them, memory as a literary theme and a historical one. But what of forgetting? This is the topic of a new book by Douwe Draaisma, author of The Nostalgia Factory: Memory, Time and Ageing (Yale University Press, 2013; 176 pages) and a professor of the history of psychology at the University of Groningen in the Netherlands. In Forgetting: Myths, Perils and Compensations (Yale University Press, 2015; 288 pages), Draaisma considers dreaming, amnesia, dementia and all the ways in which our minds—and lives—are shaped by memory’s opposite. He answered questions from contributing editor Gareth Cook.

What is your earliest memory, and why, do you suppose, have you not forgotten it?

Quite a few early memories in the Netherlands involve bicycles; mine is no exception. I was two and a half years old when my aunts walked my mother to the train station. They had taken a bike to transport her bags. I was sitting on the back of the bike. Suddenly the whole procession came to a halt when my foot got caught between the spokes of a wheel. I am pretty sure this memory is accurate because I had to see a doctor, and there is a dated medical record. It is a brief, snapshotlike memory, black-and-white. I do not remember any pain, but I do remember the consternation among my mom and her sisters.

Looking back on this memory from a professional perspective, I would say that it has the flashlike character typical for first memories from before age three; “later” first memories are usually a bit longer and more elaborate. It also fits the usual pattern of being about pain and danger. Roughly three in four first memories are associated with negative emotions. This may have an evolutionary origin: I never again had my foot between the spokes. And neither have any of my children.

“Forgetting” is usually thought about in a negative sense, but you come to it with a different perspective. Can you explain how you arrived at this way of thinking?

Experimental psychologist and memory expert Endel Tulving once counted how many different types of memory there are, and he came up with a staggering figure of 256, each with their own laws of encoding, retention, reproduction, and so on. Then it dawned on me that there must also be a multitude of types of forgetting. Considering that we forget so much more than we remember, it is fair to say that the core business of memory is forgetting. After the switch, the topics came in swift procession. Why does your colleague remember your idea but seem to forget that it was your idea? Why do portraits tend to eclipse our memories of faces? Why is there an art of memory but no art of forgetting? See?

Why does a colleague remember an idea but not whose idea it was?

This phenomenon is actually a nice demonstration of the fact that we should think of “memory” as a federation of different types of memory. Suppose you are in a meeting with colleagues, discussing some problem. You come up with a suggestion, but someone else's solution will be tried first. This situation activates two types of memories.

Autobiographical memory takes care of retaining who was there, whether it was a morning or an afternoon meeting, perhaps even what the weather was like that day. Semantic memory retains the facts of the matter: what the problem was, which solutions were suggested, and so on. The trouble is, semantic memory has trouble remembering sources and circumstances. Most of the facts you remember—such as the meaning of “incubation” or the capital of Sweden—are just the facts, and you have probably forgotten who told you or where you read this information. A week later, at a follow-up of the meeting, you may find that your colleague has retained your idea, thanks to his wonderful semantic memory but has forgotten its source—you.