The Role of Rhythm Class, Speaking Rate, and F0 in Language Discrimination

The division of languages into stress-, syllable-, and mora-timing is said to be supported by experiments showing that languages are discriminated only if they belong to different rhythm classes, a distinction said to be reflected in the duration and variability of consonantal and vocalic intervals (timing). The role of rhythm classes in discrimination is tested here along with the alternative that discrimination is due to speaking rate and F0 differences and is independent of rhythm class. Five AAX experiments with English as context (AA) and Polish, Danish, Spanish, Greek, or Korean as test (X) were conducted using the sasasa transform and modifying F0 and speaking rate, so as to compare responses to stimuli that retained the original speaking rate and F0 of each language and stimuli that were stripped of this information (speaking rate, F0, or both) while retaining their timing. Discrimination was possible both across and within rhythm classes when speaking rates differed between context and test but was largely impossible once speaking rate differences were eliminated. F0 also played a significant if less consistent role in discrimination. The changes in responses associated with speaking rate and F0 indicate that language discrimination arises from interactions between prosodic factors and that timing contributes but little. Consequently the results cast doubt both on the ecological validity of the sasasa transform, which brings timing to the fore while eliminating F0 modulation, and on the rhythm class typology said to be reflected in timing distinctions.