title: Emergence of collective memories.
abstract: BACKGROUND
  We understand the dynamics of the world around us as by associating pairs of events, where one event has some influence on the other. These pairs of events can be aggregated into a web of memories representing our understanding of an episode of history. The events and the associations between them need not be directly experienced-they can also be acquired by communication. In this paper we take a network approach to study the dynamics of memories of history.
  
  
  RESULTS
  First we investigate the network structure of a data set consisting of reported events by several individuals and how associations connect them. We focus our measurement on degree distributions, degree correlations, cycles (which represent inconsistencies as they would break the time ordering) and community structure. We proceed to model effects of communication using an agent-based model. We investigate the conditions for the memory webs of different individuals to converge to collective memories, how groups where the individuals have similar memories (but different from other groups) can form.
  
  
  CONCLUSIONS
  Our work outlines how the cognitive representation of memories and social structure can co-evolve as a contagious process. We generate some testable hypotheses including that the number of groups is limited as a function of the total population size.
authors.affiliation: Department of Physics, Umeå University, Umeå, Sweden.
authors.forename: Sungmin
authors.initials: S
authors.lastname: Lee
authors.forename: Verónica C
authors.initials: VC
authors.lastname: Ramenzoni
authors.forename: Petter
authors.initials: P
authors.lastname: Holme
mesh_terms: D002681:China; D003071:Cognition; D003142:Communication; D006801:Humans; D007406:Interview, Psychological; D008568:Memory; D008954:Models, Biological
references.citation: Psychol Rev. 2004 Apr;111(2):486-511
references.pmid: 15065919
references.citation: Science. 2002 May 3;296(5569):910-3
references.pmid: 11988575
references.citation: Phys Rev E Stat Nonlin Soft Matter Phys. 2006 Nov;74(5 Pt 2):056108
references.pmid: 17279969
references.citation: Nat Genet. 2002 May;31(1):64-8
references.pmid: 11967538
references.citation: Proc Natl Acad Sci U S A. 2002 Apr 30;99(9):5766-71
references.pmid: 16578874
references.citation: Science. 2002 Aug 30;297(5586):1551-5
references.pmid: 12202830
references.citation: Phys Rev E Stat Nonlin Soft Matter Phys. 2003 Aug;68(2 Pt 2):026112
references.pmid: 14525054
references.citation: Phys Rev E Stat Nonlin Soft Matter Phys. 2004 Nov;70(5 Pt 2):056131
references.pmid: 15600716
references.citation: Phys Rev E Stat Nonlin Soft Matter Phys. 2007 Apr;75(4 Pt 2):046111
references.pmid: 17500965