Via the MIT Collective Learning Project – The Universal Decay of Human Collective Memory (the authors): “Collective memory is believed to decay through two mechanisms, one involving communicative memory–the memory sustained by oral communication–and another involving cultural memory–the memory sustained by the physical recording of information. Yet, there is no statistical evidence showing that collective memory decays through these two mechanisms, or exploring the universality of the decay function across a variety of cultural domains. Here, we use time series data on papers and patents’ citations, and on the popularity of songs, movies, and biographies, to test the hypotheses that the decay of human collective memory involves the decay of communicative and cultural memory, and that the decay function is universal across all of these domains. We derive a mathematical model from first principles by formalizing these two mechanisms and show that the function predicted by this model provides a more accurate description of the data than previously proposed decay functions. Our results support the hypotheses that the decay of human collective memory involves the combined decay of communicative and cultural memory, and that the decay function is universal across multiple cultural domains. These findings allow us to explain the dynamics of the attention received by a piece of cultural content during its lifetime, and suggest that the dynamics of human collective memory follows a universal decay function.”