Testing the ecological validity of repetitive speech

Can one trust experiments conducted with repetitive speech to represent normal language behaviour? We compare the spectra of repetitive productions of phrases with the same phrases read from a randomised list. We use a data-driven spectral distortion measure that is trained to respond to linguistically relevant differences: it is based on a classifier that separates sounds into linguistically equivalent or not. We find that repetitive speech is not distinct from individually uttered speech. The difference between these two sorts of speech is smaller than variation within each. It is substantially smaller than typical differences between utterances produced by different subjects.