Abstract
The adaptive regulation of the trade-off between pursuing a known reward (exploitation) and sampling lesser-known options in search of something better (exploration) is critical for optimal performance. Theory and recent empirical work suggest that humans use at least two strategies for solving this dilemma: a directed strategy in which choices are explicitly biased toward information seeking, and a random strategy in which decision noise leads to exploration by chance. Here we examined the hypothesis that random exploration is governed by the neuromodulatory locus coeruleus-norepinephrine system. We administered atomoxetine, a norepinephrine transporter blocker that increases extracellular levels of norepinephrine throughout the cortex, to 22 healthy human participants in a double-blind crossover design. We examined the effect of treatment on performance in a gambling task designed to produce distinct measures of directed exploration and random exploration. In line with our hypothesis we found an effect of atomoxetine on random, but not directed exploration. However, contrary to expectation, atomoxetine reduced rather than increased random exploration. We offer three potential explanations of our findings, involving the non-linear relationship between tonic NE and cognitive performance, the interaction of atomoxetine with other neuromodulators, and the possibility that atomoxetine affected phasic norepinephrine activity more so than tonic norepinephrine activity.
Highlights
The explore-exploit dilemma refers to the question, when deciding what to do, of whether it is better to stick with a known quantity, or explore unknown options that may yield less or more value [1,2,3,4]
The Horizon Task that participants performed in our study was developed by Wilson and colleagues [4] to examine the extent to which humans use directed versus random exploration to solve the explore-exploit dilemma
We were able to look at the degree to which directed and random exploration changed from a horizon of one favoring exploitation to a longer horizon of six that should motivate exploration
Summary
The explore-exploit dilemma refers to the question, when deciding what to do, of whether it is better to stick with a known quantity, or explore unknown options that may yield less or more value [1,2,3,4]. When people make choices in an environment that includes multiple options of uncertain value, optimal performance requires a balance of both behaviors: exploitation of high-value options when they are known, and exploration of lesser known options to potentially discover better choices.
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