Two distinct exploratory behaviors in decisions from experience: comment on Gonzalez and Dutt (2011)

Gonzalez and Dutt (2011) recently reported that trends during sampling, prior to a consequential risky decision, reveal a gradual movement from exploration to exploitation. That is, even when search imposes no immediate costs, people adopt the same pattern manifest in costly search: early exploration followed by later exploitation. From this isomorphism in costless and costly search, the authors concluded that the same cognitive mechanisms underlay the control of sampling in 2 experimental paradigms employed to investigate decisions from experience: the sampling paradigm implementing costless search and the repeated-choice paradigm implementing costly search. We show that this is a misinterpretation of the human data resulting from drawing inferences about cognitive processes from data aggregated across individuals. Because of an inverse relationship between sample size and the propensity to explore, aggregating across individuals produces a pattern where exploration is gradually replaced by exploitation. On an individual level, however, there is no general reduction in exploration in the sampling paradigm. We list ensuing problems for the instance-based learning model Gonzalez and Dutt presented to explain the similarities between sampling and repeated decisions from experience.