title: Ant colonies outperform individuals when a sensory discrimination task is difficult but not when it is easy.
abstract: "Collective intelligence" and "wisdom of crowds" refer to situations in which groups achieve more accurate perception and better decisions than solitary agents. Whether groups outperform individuals should depend on the kind of task and its difficulty, but the nature of this relationship remains unknown. Here we show that colonies of Temnothorax ants outperform individuals for a difficult perception task but that individuals do better than groups when the task is easy. Subjects were required to choose the better of two nest sites as the quality difference was varied. For small differences, colonies were more likely than isolated ants to choose the better site, but this relationship was reversed for large differences. We explain these results using a mathematical model, which shows that positive feedback between group members effectively integrates information and sharpens the discrimination of fine differences. When the task is easier the same positive feedback can lock the colony into a suboptimal choice. These results suggest the conditions under which crowds do or do not become wise.
authors.affiliation: School of Life Sciences and Center for Social Dynamics and Complexity, Arizona State University, Tempe, AZ 85287, USA. tsasaki1@asu.edu
authors.forename: Takao
authors.initials: T
authors.lastname: Sasaki
authors.forename: Boris
authors.initials: B
authors.lastname: Granovskiy
authors.forename: Richard P
authors.initials: RP
authors.lastname: Mann
authors.forename: David J T
authors.initials: DJ
authors.lastname: Sumpter
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Pratt
mesh_terms: D000819:Animal Communication; D000818:Animals; D001000:Ants / Q000502:physiology*; D002755:Choice Behavior / Q000502:physiology; D004192:Discrimination, Psychological / Q000502:physiology*; D005246:Feedback; D006126:Group Processes; D008954:Models, Biological; D009425:Nesting Behavior / Q000502:physiology*
keywords: biological complexity; group cognition; psychophysics; social insects
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