title: Incipient cognition solves the spatial reciprocity conundrum of cooperation.
abstract: BACKGROUND
  From the simplest living organisms to human societies, cooperation among individuals emerges as a paradox difficult to explain and describe mathematically, although very often observed in reality. Evolutionary game theory offers an excellent toolbar to investigate this issue. Spatial structure has been one of the first mechanisms promoting cooperation; however, alone it only opens a narrow window of viability.
  
  
  RESULTS
  Here we equip individuals with incipient cognitive abilities, and investigate the evolution of cooperation in a spatial world where retaliation, forgiveness, treason and mutualism may coexist, as individuals engage in Prisoner's Dilemma games. In the model, individuals are able to distinguish their partners and act towards them based on previous interactions. We show how the simplest level of cognition, alone, can lead to the emergence of cooperation.
  
  
  CONCLUSIONS
  Despite the incipient nature of the individuals' cognitive abilities, cooperation emerges for unprecedented values of the temptation to cheat, being also robust to invasion by cheaters, errors in decision making and inaccuracy of imitation, features akin to many species, including humans.
authors.affiliation: Applications of Theoretical Physics Group, Centro de Matemática e Aplicações Fundamentais, Complexo Interdisciplinar da Universidade de Lisboa, Lisboa, Portugal.
authors.forename: Jeromos
authors.initials: J
authors.lastname: Vukov
authors.forename: Francisco C
authors.initials: FC
authors.lastname: Santos
authors.forename: Jorge M
authors.initials: JM
authors.lastname: Pacheco
mesh_terms: D003071:Cognition / Q000502:physiology*; D003299:Cooperative Behavior; D005716:Game Theory; D006801:Humans; D007398:Interpersonal Relations; D008960:Models, Psychological