Cognitive affordances of South Scandinavian Mesolithic portable art as inferred from complexity and entropy measures

Unravelling the complex dynamics of past symbolic behaviour is challenging using traditional archaeological approaches alone. Drawing on the cognitive sciences, we here present novel computational measures of the portable art of Mesolithic South Scandinavia. The anthropogenic ornamentation on archaeological artefacts is quantified by calculating Shannon information entropy and perimetric complexity. These two methods in combination – measuring each decorated artefact's ‘information’ content and degree of ‘visual complexity’ respectively – allow for a mapping of diachronic developments of motif morphology. The results are interpreted within a cognitive affordance framework, in which the social functions of the decorations are inferred by interrogating which morphological traits were subjected to selective pressure. Results suggest a notable Middle Mesolithic peak in visual complexity, coupled with a slight, gradual increase in information content over time. We thus demonstrate non-linear developments of ornamentation practices across the Mesolithic and interpret this to index the emergence of fundamentally different societal functions of these ornamentations. These shifts correlate broadly with and are likely driven by environmental and demographic changes. • Cognitive affordance framework applied to the South Scandinavian Mesolithic portable art corpus. • Perimetric complexity and Shannon entropy quantifies decorative richness and motif variability. • Findings suggest non-linear temporal trajectories of stylistic traditions. • Middle Mesolithic peak in visual complexity, Late Mesolithic specialisation of motif usage.