This study investigates whether there is a universal tendency for content
interrogative words (wh-­words) within a language to sound similar in order to facilitate
pragmatic inference in conversation. Gaps between turns in conversation are very
short, meaning that listeners must begin planning their turn as soon as possible.
While previous research has shown that paralinguistic features such as prosody and
eye gaze provide cues to the pragmatic function of upcoming turns, we hypothesise
that a systematic phonetic cue that marks interrogative words would also help early
recognition of questions (allowing early preparation of answers), for instance wh-­
words sounding similar within a language. We analyzed 226 languages from 66
different language families by means of permutation tests. We found that initial
segments of wh-­words were more similar within a language than between languages,
also when controlling for language family, geographic area (stratified permutation)
and analyzability (compound phrases excluded). Random samples tests revealed that
initial segments of wh-­words were more similar than initial segments of randomly
selected word sets and conceptually related word sets (e.g., body parts, actions,
pronouns). Finally, we hypothesized that this cue would be more useful at the
beginning of a turn, so the similarity of the initial segment of wh-­words should be
greater in languages that place them at the beginning of a clause. We gathered
typological data on 110 languages, and found the predicted trend, although statistical
significance was not attained. While there may be several mechanisms that bring
about this pattern (e.g., common derivation), we suggest that the ultimate explanation
of the similarity of interrogative words is to facilitate early speech-­act recognition.
Importantly, this hypothesis can be tested empirically, and the current results provide
a sound basis for future experimental tests.