Experimental evidence of transitive inference in black-capped chickadees
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Many recent discoveries in animal cognition have shown that species once thought to be relatively simple are in fact capable of complex problem-solving in accordance with their ecological needs. These findings have resulted from experiments designed with the evolutionary history of the focal species in mind. Transitive inference (TI), the abiliy to infer the ordering of non-adjacent objects within a series, is a cognitive skill once thought to be exclusive to humans. Now considered a litmus-test for logical-relational reasoning, TI is thought to have evolved in social species in order to help track dominance relationships. Although recent work has shown that animals can display TI, it has yet to be demonstrated in the natural context in which it evolved. Songbirds may use TI to gain relative dominance information about others during countersinging interactions, through their use of network communication. Here I demonstrate that black-capped chickadees (Poecile atricapillus) use TI to judge the relative rank of unknown territorial intruders during the breeding season using dominance information provided through song contests. Using a multispeaker playback, I provided focal males with the relative ranks of three simulated “males” through two countersinging interactions (A > B, B > C). I predicted that when presented with the non-adjacent pair (A and C) with no relative rank information provided, focal males would choose to defend against the intruder they perceived as the greater threat. Consistent with my predictions, the majority of focal males approached “male” A. Additionally, male responses were influenced by age, with older males (in their second or later breeding season) approaching the dominant intruder more consistently than younger males (in their first breeding season). This is the first instance of TI being demonstrated in a natural population of untrained animals, and has important implications for the understanding of songbird communication networks. Transitive inference may be used in several natural situations by chickadees throughout the breeding season and a number of possible avenues for future TI research are discussed. Additionally, methods are suggested for the examination of TI during the non-breeding season.