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Positive Frequency Dependence in Graffiti: An Empirical Case Study of Cultural Evolution

Abstract Cultural traits can be seen to evolve by a process similar to natural selection. They are transmittable, variable, and the variants can have differential fitness. As a result, cultural evolution can in principle lead to non-random distribution of cultural traits. A limited number of studies have addressed the evolution of human cultural traits “in the wild,” partly because culture is difficult to categorize into discrete units. Parallel to studying non-random species distributions in ecosystems due to natural selection, we have focused on investigating non-random distributions of cultural traits in a local environment. We used a collection of library study desks to categorize graffiti into content-based cultural traits, or “topics”, and quantified the level of clustering for each topic as a measure of non-random distributions of topics on the desks. Clustering was found to occur for some topics but not others, and the level of clustering varied with topic in ways that are consistent with topic content characteristics.