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COMPUTATIONAL SOCIAL SCIENCE Predicting the decay of collective memory Cultural products have a life of their own: academic papers get cited and songs get downloaded. Surprisingly, public attention to these products shows a consistent pattern over time: a constant decline characterized by an infexion point. This pattern might be due to how cultural products are discussed in the community and archived as cultural memories. Alin Coman

ake the public attention to the 9/11 songs rated on Spotify. For each cultural terrorist attacks as an example. product, they operationalize public attention TDays after the attacks, New Yorkers in different ways: for papers, how many tended to congregate in small groups of new citations an academic paper received close friends to discuss the events and for a period of time after publication, while their experiences1. They communicated for movies, how many views their trailers with one another as a way to share had on YouTube for a period of time after information and to cope with the trauma. release. They then fit three mathematical Following the immediate aftermath of functions to try to approximate the observed the 9/11 events, makeshift memorials, pattern of public attention: an exponential newspaper articles, books on the topic decay function, a bi-exponential decay and formal commemorations served as function and a log-normal decay function. constant reminders of the terrible tragedy. Results show that a bi-exponential function Both the communicative exchanges that (that is, decay of attention interrupted by occurred right after the attacks (that is, an inflexion point) constituted the best fit communicative memories) as well as of the data. More surprisingly, this decay the artefacts that served as reminders in pattern describes all the types of cultural the wake of the attacks (that is, cultural products they tested. memories) fundamentally impacted the While previous studies established that collective memories of New Yorkers. Writing one cannot predict whether a particular in Nature Human Behaviour, remarkably, cultural product would be successful Candia and colleagues2 now show that there Credit: Roy Scott/Ikon Images/Getty or not on the market5, this paper indicates might be a universal pattern of decay of that once it’s out there in the world, attention that characterizes a wide range of we know how the public attention to cultural products, from academic papers the product will decay over time: in a describing the Higgs boson to Taylor reveal the fundamental forces that shape bi-exponential fashion. Swift’s ‘Shake it Off’. This universal decay is societies’ collective memories4. In contrast, There is tremendous promise in the circumscribed by the two factors illustrated psychologists conceptualize collective current approach, but further refinement is in the 9/11 example: the communicative memories as shared individual memories certainly warranted. First, as useful as this interactions occurring right after the release that bear on people’s identities3. For them, framework differentiating communicative of a cultural product and the physical the main factors that shape collective and cultural memories is, empirical records that are subsequently established. memories go beyond the forces that are evidence of its explanatory power is just The main contribution of the paper is in responsible for creating objectified symbols. tentative. It is inferred that the observed taking a big-data approach to exploring the Rather, it is the reception and filtering pattern is produced by forces that involve dynamics of collective attention, and by through people’s minds of the information communicative and cultural memory, but extension, to understanding the formation present in the environment (for example, the this assumption has not yet been tested. of collective memories. textbook or monument) that is of interest Therefore, more direct evidence of this The topic of the formation of collective to psychologists. Candia and colleagues potential mechanism of collective attention memories has been intensely debated take a big-data approach to understand how should be sought. Second is the question of among the social sciences3. Sociologists collective memories — operationalized as universality: how universal is the pattern tend to conceptualize collective memories public attention — are influenced by both observed? Papers, patents, songs and movies as objectified symbols that have a physical the conversations that people have with might show this bi-exponential pattern, manifestation. Textbooks, monuments and one another as well as by the artefacts but other cultural products that clearly fall memorials represent the instantiation of that are created following initial under the category of collective memories collective memories in society. Sociologists communicative interactions. (for example, the 9/11 terrorist attacks) are mainly interested in understanding the The approach taken by the authors might predictably show a different pattern. structural and institutional struggles that involves collecting data that captures the In the case of the 9/11 events, one could play out as these objectified symbols are public attention given to a wide range of imagine that a cyclical pattern indicating constructed, demolished and reconstructed. cultural products, from academic papers renewed communicative processes at every These struggles, sociologists contend, published in a physics journal to popular commemoration (that is, sinusoidal decay)

Nature Human Behaviour | www.nature.com/nathumbehav news & views would more accurately describe the decay point could have real-world consequences. Alin Coman of collective memories. Consideration of For instance, Hurricane Sandy had horrible Princeton University, Princeton, NJ, USA. violations of the general pattern discovered consequences for New Yorkers in 2012, e-mail: [email protected] by Candia and colleagues2 has the potential with extensive flooding and electricity to lead to the meaningful expansion of the loss for parts of Manhattan for weeks. The Published: xx xx xxxx proposed model. communicative processes following the https://doi.org/10.1038/s41562-018-0480-7 Finally, the present research has hurricane could only be sustained for a References meaningful practical implications. limited period of time, a period in which 1. Mehl, M. R. & Pennebaker, J. W. Psychol. Sci. 14, 579–585 (2003). What are the factors that might expand individuals in the New York region probably 2. Candia, C., Jara-Figueroa, C., Rodriguez-Sickert, C., Barabási, A.-L. & Hidalgo, C. A. Nat. Hum. Behav. https://doi. or contract the inflexion point of the adjusted their beliefs about climate change. org/10.1038/s41562-018-0474-5 (2018). bi-exponential function? Previous research Once these communicative processes 3. Hirst, W., Yamashiro, J. & Coman, A. Trends Cogn. Sci. 22, has shown that these factors range from are attenuated and no artefacts serve as 438–451 (2018). 4. Olick, J. K. Sociol. Teory 17, 333–348 (1999). obvious psychological phenomena reminders, the collective attention — and 5. Salganik, M. J., Dodds, P. S. & Watts, D. J. Science 311, (that is, emotion elicited by particular memory — of the severity of the hurricane 854–856 (2006). cultural products6) to socio-structural decays, and with it, the belief that climate 6. Brady, W. J., Wills, J. A., Jost, J. T., Tucker, J. A. & Van Bavel, J. J. ones (that is, network connectivity that change is endangering life on the planet. Proc. Natl Acad. Sci. USA 114, 7313–7318 (2017). 7. Coman, A., Momennejad, I., Geana, A. & Drach, D. R. Proc. Natl characterizes the community in which Understanding how one could delay the Acad. Sci. USA 113, 8171–8176 (2016). the cultural products diffuse7). These inflexion point of the bi-exponential 8. Rogers, T., Milkman, K. L. & Volpp, K. G. M. J. Am. Med. Assoc. expansion/contraction dynamics are function could offer policymakers much 311, 2065–2066 (2014). critically important, since being able needed time to lock in commitment devices Competing interests to extend the communicative inflexion at a population level8. ❐ The author declares no competing interests.

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