An other important role of prosody is in the plausibility of context. The Chomsky [14] example;
time flies like an arrow, in which prosody marks flies as a verb is entirely different than;
fruit flies like a banana, in which flies is a noun. To utter the second sentence using the initial sentence's intonation, renders it insensible. The first part of the sentence sets one up for a kind of syntactic structure and fails to deliver the rest of it, such that appropriate effects are not generated.
Sometimes the puzzle can be resolved by changing the scope arrangement;
I will have breakfast only if there is not enough food, sounds somewhat ruthless. The more likely interpretation changes the scope arrangement to;
I will have breakfast only, if there isn't enough food.
The habituation that comes from exposure to a specific language create expectations about a syntactic stream. When prosody fails to generate specific effects, for the reasons that have been discussed, changes occur in the use of vocables. As a result they find themselves in new syntactic environments.
One of the reasons for functionalization is the failure of prosody to sustain a long string of previously used vocables. The functionalization of certain vocables is an attempt to preserve a causal flow in which prosody creates expectations. Expectations result from exposure to a specific language. For example, a few bars of a well know song will entice someone to finish the melody. Prosody plays a similar role in language. A few bars of a well known linguistic construction creates expectations about the rest of the phrase. Unfamiliar constructions require new synaptic structures. Without sensorially immediate triggers to stimulate these new pathways, one has to rely on endogenous stimuli to generate effects. Prosody can provide some of the necessary triggering in the event that some of the syntactic aspects of an unusual construction fails to provide clear expectations.
Some aspects of attenuation can be understood in those terms, as well, and functionalized vocabulary is a result of this dynamics.