Behavioral Ecology and Sociobiology

, Volume 65, Issue 3, pp 547–558 | Cite as

Darwin’s “tug-of-war” vs. starlings’ “horse-racing”: how adaptations for sequential encounters drive simultaneous choice

  • Alex Kacelnik
  • Marco Vasconcelos
  • Tiago Monteiro
  • Justine Aw


Charles Darwin aided his private decision making by an explicit deliberation, famously deciding whether or not to marry by creating a list of points in a table with two columns: “Marry” and “Not Marry”. One hundred seventy-two years after Darwin’s wedding, we reconsider whether this process of choice, under which individuals assign values to their options and compare their relative merits at the time of choosing (the tug-of-war model), applies to our experimental animal, the European Starling, Sturnus vulgaris. We contrast this with the sequential choice model that postulates that decision-makers make no comparison between options at the time of choice. According to the latter, behaviour in simultaneous choices reflects adaptations to contexts with sequential encounters, in which the choice is whether to take an opportunity or let it pass. We postulate that, in sequential encounters, the decision-maker assigns (by learning) a subjective value to each option, reflecting its payoff relative to background opportunities. This value is expressed as latency and/or probability to accept each opportunity as opposed to keep searching. In simultaneous encounters, choice occurs through each option being processed independently, by a race between the mechanisms that generate option-specific latencies. We describe these alternative models and review data supporting the predictions of the sequential choice model.


Choice Latency Sequential choice model Tug-of-war model Sturnus vulgaris 


Author note

This work was supported by Biotechnology and Biological Sciences Research Council Grant BB/G007144/1 to AK. MV, TM, and JA were supported by an Intra-European Marie Curie Fellowship, a doctoral grant from the Portuguese Foundation for Science and Technology, and a Biotechnology and Biological Sciences Research Council Fellowship, respectively. We are grateful to Miguel Rodriguez-Gironés for discussions and advice.

Conflict of Interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Alex Kacelnik
    • 1
  • Marco Vasconcelos
    • 1
  • Tiago Monteiro
    • 1
  • Justine Aw
    • 1
  1. 1.Department of ZoologyUniversity of OxfordOxfordUK

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