Comparing models of semantic fluency: Do humans forage optimally, or walk randomly?

AbstractHills, Jones, and Todd (2012) observed that response patterns during the semantic fluency task (e.g., “name all the animals you can in a minute”) displayed statistical signatures of memory search that mirror optimal foraging in physical space. They proposed a model of memory search based on exploitation-exploration tradeoffs known to produce optimal foraging patterns when animals search for food resources, applied to a spatial model of semantic memory. However, Abbott, Austerweil, and Griffiths (2015) demonstrated that optimal foraging behavior could also naturally emerge from a random walk applied to a network representation of semantic memory, without reliance on a foraging process. Since then, this has been a very active are of debate in the literature, but core confounds have prevented any clear conclusions between the random walk and foraging model. We control confounds here by using a fixed training corpus and learning model to create both spatial and network representations, and evaluate the ability of the foraging model and several variants of the random walk model to produce the behavioral characteristics seen in human data. Further, we use BIC to quantitatively compare the models’ ability to fit the human data, an obvious comparison that has never before been undertaken. The results suggest a clear superiority of the optimal foraging model. The mechanism used to search memory in the fluency task is likely to have been exapted from mechanisms evolved for foraging in spatial environments.

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