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

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.