Zipf’s Law for Speech Acts in Spoken English

Speech acts, as basic communication units in pragmatics, are highly correlated to speakers' communicative intentions. It is a worthwhile goal to explore whether they obey some linguistic laws that reflect people's cognitive mechanisms, e.g. Zipf's Law. However, few studies have examined whether the Zipf distribution can capture the frequencies of speech acts, and whether its parameters can show how speakers' attributes (e.g. gender and education level) relate to the use of speech acts. As a preliminary attempt to bridge this gap, the current study finds from the data sample of the Switchboard Dialog Act Corpus that: (1) the Zipf distribution well captures the distribution of speech acts; (2) the parameter a can distinguish the dialogues between speakers of different genders, and it shows a regularity of the highest frequency of an SA in a dialogue to some degree; (3) the parameter b can differentiate speakers of different education levels – people with college-level education may have higher expressivity of SAs compared with those with higher-than-college-level education. This study shows that Zipf's Law can be extended to the analysis of pragmatic phenomena, which may become part of the synergetic system of language through the approach of Quantitative Linguistics.