Unconscious thought and deliberation without attention: A miracle or a mirage?

Since the time of Sigmund Freud (1856–1939), people have been fascinated by the possibility of a powerful and influential ‘unconscious’ that controls much of our behaviour. Though Freud conceives of this unconscious largely in terms of emotional urges and powers to suppress these urges, a more cognitive interpretation in terms of mental processes is highly feasible [1, 2]. Most of us will probably occasionally have the experience of suddenly ‘seeing’ the solution to a problem, or suddenly ‘knowing what to choose,’ after having been distracted for a while by other concerns. It is tempting to conclude from such experiences that, while we were distracted, some form of unconscious processing of the problem has continued which then resulted in the correct solution or choice ‘popping up’ in our consciousness. Basically, this was the point of departure for Dijksterhuis to develop his unconscious thought theory and the associated notion of ‘deliberation without attention’ [3–5]. According to this theory, unconscious thought leads to better performance, in particular in complex tasks, than conscious thought. The question is, how credible is this view? To begin with, as Bonke et al. [6] aptly note, Dijksterhuis et al.’s unconscious thought theory diverges from mainstream views of human (un)consciousness, i.e. the dual system theories [7–9] which recently became popular among a much broader audience after the release of Daniel Kahneman’s 2011 book Thinking, fast and slow [10]. These theories distinguish two processing systems: one that operates fast, automatically, holistically, intuitively, and unconsciously (‘System 1’) and one that