The present study explored the relation between pitch and phonological perception of tone in the Surui language of Rondonia (Brazil), given that pitch realization of tone in Surui is a complex phenomenon. F0 values and pitch contour of the vowel nucleus were found to influence the perception of tone in this language of the Monde family, but these effects were found to be dominated by the influence of the pitch contour of the preceding syllable. These perceptual results, completed by an analysis on production, contribute to indicate the existence of a Mid tone in Surui, allophone of the High tone, which would be the result of a regressive downstep.

Index Terms: Tone perception, Suruí language, Mondé languages, AXB test, downstep