I am a Chargé de Recherches at the Centre National de la Recherche Scientifique (France), and a research group leader at the Max Planck Institute for the Science of Human History in Jena (Germany). I study cultural transmission, the way traditions are passed on from person to person. This key mechanism in human history and evolution bridges three distinct levels: individual human cognition, interactions between individuals, and population-level processes. To span all these levels, my work combines a broad range of methods, from lab experiment to quantitative cultural history. In my book How Traditions Live and Die (2016), I developed a theory of cultural transmission which argues that it rests primarily on ostensive communication, as opposed to imitation. I also defended a view of cultural evolutionary dynamics where continuous, non-random transformations matter more to cultural change than selectionist dynamics, leading to debates on the nature and implications of cultural-evolutionary models. Since 2016, I have focused my research on one particular tool for cultural transmission: graphic codes. Writing systems, pictographs, emblems, brands and seal markings are all graphic codes: they carry information by means of enduring images with standardised meanings. I have studied the visual characteristics of letters and emblems from a perspective that combines cognitive science with cultural evolution. I seek to understand how the shape of letters and other symbols maximises the information they can carry while adapting to the constraints of human visual cognition.