Over the past 50 years Nobel laureate Eric R. Kandel has shaped our understanding of the basic mechanisms of memory through his studies of the primitive sea slug Aplysia [see “Eric Kandel: From Mind to Brain and Back Again,” by David Dobbs, Scientific American Mind; October/November 2007]. First a student of history and literature and later a psychiatrist, the Vienna-born Columbia University professor and Howard Hughes Medical Institute investigator has emerged as one of the most prominent brain researchers of the century.

Scientific American Mind: Do you see the humanities and natural sciences as separate realms, or can they be unified?
Eric Kandel: I think they can—and the biology of the mind is one of ­several possible bridges between them. But unfortunately, today people from different academic backgrounds do not meet and talk to each other so much. This was once quite different. For example, in Vienna at the end of the 19th century, uncovering the unconscious was a project shared by scientists, artists and writers alike. People such as [writer and doctor] Arthur Schnitzler, [painters] Gustav Klimt and Egon Schiele, and [artist, poet and playwright] Oskar Kokoschka exchanged their ideas with scientists and other intellectuals and scientists in literary circles.

Mind: Do you regard Freud as a ­scientist?
Kandel: His aim was clearly scientific, but his methods weren’t. Until 1894 Freud tried to develop a neurobiological view of the mental apparatus. But because of the limited knowledge of his time, he finally gave up on that idea. Although Freud kept on working in a fairly systematic way, his ideas lacked an empirical foundation. But to my mind, the problems with psychoanalysis arose with those who came later. Freud’s followers should have tried to verify at least some of Freud’s postulates using empirical methods. Instead they treated him as if he were a guru. Nevertheless, we have profited from Freudian ideas. For example, he bridged the gap between mental disease and mental health, seeing the same unconscious mechanisms at work in both.

Mind: Why is the unconscious so fascinating to us?
Kandel: Because 80 to 90 percent of what we do is unconscious. When we speak, we use presumably correct grammatical structures while paying little if any conscious attention to this grammar. And we act in lots of other ways without having the slightest clue what we are actually doing. Much of our urge to understand the unconscious arises from the spooky feeling that there is something within us governing our actions.

Mind: How does the modern understanding of unconscious processes differ from Freud’s?
Kandel: Freud first proposed one fundamental driving force, the libido, and later, in response to the horrors of the First World War, added the “death impulse” Thanatos. These are very broad categories that brain research cannot really deal with. But Freud did not think there was a unified unconscious. ­Instead he came up with a topology of different forms: the implicit unconscious representing motor and perceptual skills, the preconscious filled with material we can readily become aware of, and the dynamic unconscious in which, for example, instinctive impulses are suppressed. With modern neuroimaging techniques, we are finally able to discover what the brain is doing during conscious or different forms of unconscious processing.

Mind: We tend to think of memory as a kind of library that holds a record of events and facts that can be retrieved as needed. Is this an accurate metaphor?
Kandel: No, memory is not like that at all. Human memory reinvents itself all the time. Every time you remember something, you modify it a little bit, in part dependent on the context in which you recall it. That is because the brain’s storage is not as exact as written text. It is always a mixture of many facades of the past event: images, pictures, feelings, words, facts and fiction—a “re-collection” in the true sense.