Reward, Risk and Ambiguity in Human Exploration: A Wheel of Fortune Task

In realistic environments, organisms are frequently faced with multiple resource alternatives, and must balance the tradeoff between pursuing the known options (exploitation), and searching the environment for unknown opportunities (exploration). Exploration can be most beneficial in the presence of environmental uncertainty when the range and benefits of all reward options are not fully known, exploration can lead to the discovery of new, better resources and an ultimately higher overall reward. However, uncertainty can take many forms, and it is unclear how different types of uncertainty impact people's exploratory behaviour. We used a 'wheel of fortune' task to separate two well-established sources of uncertainty: risk (when outcomes are stochastic, but the probabilities of outcomes are known) and ambiguity (when the probabilities and/or the outcomes are unknown), and examine how they impact exploration. The results suggest that the presence of ambiguity in the environment drives people to explore in order to acquire more information and reduce the ambiguity. Conversely, a higher risk level in the environment increases exploration by increasing decision noise and making people less sensitive to the reward values of the available options. We examined these effects under two different decision horizons, and found that ambiguity-, and not risk-related exploration increases with decision horizon. These findings imply that different sources of uncertainty impact exploration differently, and may shed light on the mechanisms behind two distinguishable types of exploration that have been previously identified: random (characterized by an increase in decision noise) and directed (information-seeking) exploration.