11.1 What Is Prosody?

The sounds of language express meaning both verbally and nonverbally (Crystal 1995). Verbal meaning refers to the use of vowels and consonants to build up words, phrases, and sentences. Chapter 10 is concerned with verbal meaning in engineered dialogs, but the conversational wording of prompts is only half the story. The other half is how the message is delivered. To impart structure and expression to meaning, speakers use intonation, stress, rhythm, tone of voice, and silence in the form of pauses. Linguists refer to this nonverbal meaning as prosody.

Many of the same issues that you must consider to achieve naturalness in prompt wording also account for naturalness of prosody. It is not enough to consider only the linguistic structure of prompts as they appear in written form. The focus should be on how the user will hear them in context, which is fundamental in shaping the prosody of utterances in human-to-human interactions. This chapter outlines the basics of prosody and explains its importance in encoding and decoding meaning.

Prosody is a level of linguistic analysis that is systematic and principled. Prosody is an element of grammar, the implicit knowledge that native speakers have about their language.^[1] Just as syntax is a component of grammar, so is prosody. Of course, we would never intentionally write prompts that defy the rules of syntax, as in "Please to say now you PIN," so we must not ignore basic rules of prosody. This chapter demonstrates how attention to prosody pays off in interactions that are more comprehensible and more comfortable for the VUI user.

^[1] In this chapter we use a broader definition of "grammar" than earlier in the book. Earlier, we used "grammar" to refer to the language knowledge we, as designers and grammar developers, supply to the machine. Here, it is used more generally to refer to the language knowledge a human has.