  Collective memory is a common representation of the past shared by a group of
people that modulates its identity. Recent literature on computational social
science quantifies collective memories using expressions of those memories
operationalized as the amount of collective attention focused on specific
cultural icons, either artifacts or people. We model the temporal dynamics of
collective memory using a two-step decay process, characterized by a
short-lived and intense initial stage followed by a long-lived and milder
decline of collective attention. Different collective memory mechanisms sustain
the two-step process. The first is communicative memory, which corresponds to
all memories supported by socializing acts. The second is cultural memory,
which corresponds to all memories sustained by accessing records. Thus, this
model predicts a transition time when cultural memory overcomes communicative
memory. It has practical consequences related to shrinking or extending the
time a specific topic is part of a community's conversation, i.e.,
communicative memory, empowering policymakers with valuable time to generate
solutions and compromises for contingent and public problems.
