Epistemic Curiosity Activates Reward Circuitry and Enhances Memory

Curiosity has been described as a desire for learning and knowledge, but its underlying mechanisms are not well understood. We scanned subjects with functional magnetic resonance imaging while they read trivia questions. The level of curiosity when reading questions was correlated with activity in caudate regions previously suggested to be involved in anticipated reward. This finding led to a behavioral study, which showed that subjects spent more scarce resources (either limited tokens or waiting time) to find out answers when they were more curious. The functional imaging also showed that curiosity increased activity in memory areas when subjects guessed incorrectly, which suggests that curiosity may enhance memory for surprising new information. This prediction about memory enhancement was confirmed in a behavioral study: Higher curiosity in an initial session was correlated with better recall of surprising answers 1 to 2 weeks later. Curiosity is the complex feeling and cognition accompanying the desire to learn what is unknown. Curiosity can be both helpful and dangerous. It plays a critical role in motivating learning and discovery, especially by creative professionals, increasing the world’s store of knowledge. Einstein, for example, once said, ‘‘I have no special talents. I am only passionately curious’’ (Hoffmann, 1972, p. 7). The dangerous side of curiosity is its association with exploratory behaviors with harmful consequences. An ancient example is the mythical Pandora, who opened a box that unleashed misfortunes on the world. In modern times, technology such as the Internet augments both good and bad effects of curiosity, by putting both enormous amounts of information and potentially dangerous social encounters a mouse-click away. Despite the importance of human curiosity, its psychological and neural underpinnings remain poorly understood. Philosophers and psychologists have described curiosity as an appetite for knowledge, a drive like hunger and thirst (Loewenstein, 1994), the hunger pang of an ‘‘info-vore’’ (Biederman & Vessel, 2006, p. 247), and ‘‘the wick in the candle of learning’’ (William Arthur Ward, cited by Wikiquote, 2008). In reinforcement learning, a novelty bonus is used to motivate the choice of unexplored strategies (Kakade & Dayan, 2002). Curiosity can be thought of as the psychological manifestation of such a novelty bonus. A theory guiding our research holds that curiosity arises from an incongruity, or information gap—a discrepancy between what one knows and what one wants to know (Loewenstein, 1994). This theory assumes that the aspired-to level of knowledge increases sharply with a small increase in knowledge, so that the information gap grows with initial learning. When one is sufficiently knowledgeable, however, the gap shrinks, and curiosity falls. If curiosity is like a hunger for knowledge, then a small ‘‘priming dose’’ of information increases the hunger, and the decrease in curiosity from knowing a lot is like being satiated by information. Address correspondence to Colin F. Camerer, Division of Humanities and Social Sciences, California Institute of Technology, Pasadena, CA 91125, e-mail: [email protected]. PSYCHOLOGICAL SCIENCE Volume 20—Number 8 963 Copyright r 2009 Association for Psychological Science In the information-gap theory, the object of curiosity is an unconditioned rewarding stimulus: unknown information that is anticipated to be rewarding. Humans (and other species, such as cats and monkeys) will expend resources to find out information they are curious about, much as rats will work for a food reward (Loewenstein, 1994). On the basis of this observation, we hypothesized that the striatum would be linked to curiosity because a growing body of evidence suggests that activity in the human striatum is correlated with the level of reward signals (Hare, O’Doherty, Camerer, Schultz, & Rangel, 2008; Knutson, Westdorp, Kaiser, & Hommer, 2000; McClure, York, & Montague, 2004; O’Doherty, 2004). Guided by these ideas, we explored the neural correlates of curiosity in one study and tested the hypotheses derived from its findings in two additional studies. In all studies, subjects were presented with a series of trivia questions chosen to create a mixture of high and low epistemic curiosity (Fig. 1a). Subjects read each question, guessed the answer, rated their curiosity about the question, and rated how confident they were that they knew the answer (P). Then the question was presented again, followed by the correct answer (Fig. 1b). In the first experiment, subjects read the questions during functional magnetic resonance imaging (fMRI). In the second experiment, they performed the same task without scanning, and their memory for answers was tested in a follow-up session 1 to 2 weeks later. In the third experiment, we behaviorally tested whether curiosity is indeed a form of reward anticipation.