Resolve why higher-harmonic coefficients fail to transfer across cue designs

Resolve whether the failure of higher-harmonic coefficients to transfer between the two-target and three-target cue designs results from animal-to-animal variation in the second-harmonic coefficient, inadequacy of the two-harmonic truncation, or a genuine breakdown of the shared-spectrum assumption.

Background

The first-harmonic response generalizes across cue geometries and recordings, but fitted higher harmonics do not. In particular, the second-harmonic coefficient measured in the two-target design does not predict the three-target recordings. The paper identifies several possible explanations, including biological variation, model truncation, and failure of a common spectrum, but does not distinguish among them.