Relative comparisons of call parameters enable auditory grouping in frogs

Whereas many studies on mate choice have measured the relative attractiveness of acoustic sexual signals, there is little understanding of another critical process: grouping and assigning the signals to their sources. For female túngara frogs, assigning the distinct components of male calls to the correct source is a challenge because males sing in aggregations, producing overlapping calls that lead to perceptual errors analogous to those of the 'cocktail party problem'. Here we show that for presentation of >2 call components, however, subjects are more likely to group the two components with the smallest relative differences in call parameters, including relative spatial separation (a primitive acoustic cue) and relative similarity to the species-specific call sequence (a schema-based cue). Thus, like humans, the cognitive rules for the perception of auditory groups amidst multiple sound sources include the use of relative comparisons, a flexible strategy for dynamic acoustic environments.