Data from: Self-deception in nonhuman animals: weak crayfish escalated aggression as if they were strong

  • Michael Angilletta (Contributor)
  • Robbie S. Wilson (Contributor)
  • Gregory Kubitz (Contributor)



Humans routinely deceive themselves when communicating to others, but no one knows whether other animals do the same. We ask whether dishonest signaling between crayfish meets a condition required for self-deception: dishonest individuals and honest individuals escalate aggression according to their signals of strength rather than actual strength. Using game theory, we predicted how an animal’s knowledge of its strength should affect its decision to escalate aggression. At the evolutionary equilibrium, an animal that knows its strength should escalate aggression according to its strength, relative to the expected strength of its opponent. By contrast, an animal that knows only its size should escalate aggression according to its size, relative to the size of its opponent. We tested these predictions by staging encounters between male crayfish (Cherax dispar) of known sizes and strengths. Consistent with a model of self-deception, crayfish escalated aggression based on the sizes of their claws relative to those of their opponents, despite the fact that size poorly predicts strength. Males who were weak for their size escalated disputes less often, but their aggression far exceeded the level predicted by a model of self-awareness, suggesting these crayfish were largely ignorant of their deception. Animals that fail to recognize their own dishonest signals may win disputes with stronger opponents without engaging in costly combat. Our game-theoretical approach can be used to identify potential cases of self-deception in nonhuman animals, enabling comparative studies of this behavior.,PCA.dataSeven linear measurements of claw size and one estimate of maximal claw force for left and right claws of crayfishregression.dataoutcomes of staged encounters with crayfish of known size and strength. Variables are as follows: A) crayfish ID; B & C) mean.size estimated as a score for PC1 and mean.force of the focal crayfish's pair of claws; D) random effect of focal crayfish from model of force predicted by size; E) mean residual force of the pair of claws from a regression of force onto size; F & G) minimal and maximal residual force (i.e., residua strength of weaker and stronger claw, respectively); H) difference in residual strength of stronger and weaker claw; I) ID of opponent crayfish; J) random effect of opponent crayfish from model of force predicted by size; L) opponents size estimate as a score for PC1; M) force of opponent's claws expected from their mean size; N) outcome of encounter, where 0 means focal crayfish fled and 1 means it escalated aggression; O) difference in mean size between focal crayfish and its opponent; P) difference in mean force between focal crayfish and its opponent; Q) difference between mean force of focal crayfish and the expected force of its opponent, given the opponent's mean claw size;,
Date made availableSep 28 2019

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