“Uh” is preferred by male speakers in informal presentations in American English

This study investigates factors that are likely to be related to speakers' choice of filler type between uh and um in English, using an informal presentation speech corpus. The effects of the following factors on the probability of each filler type was examined: (1) immediately preceding clause boundary depth, (2) clause size measured as the number of words in the clause, (3) the number of quotation remarks in the clause, and (4) speaker's sex. The filler probabilities increased with the boundary depths. This trend was much stronger with um than with uh. Ums are more likely to appear clause-initially than uhs. Clause size had similar effect sizes on the two filler types. The number of quotation remarks had a stronger negative effect with ums. Speaker's sex had a significant effect only with uhs. Uhs are used more frequently by male speakers than by female speakers. The results indicate that speakers' choice of filler type is affected by the combination of multiple factors with various effect sizes.