Speech is Optimized

Next, we assume that speech is optimized for the speaker's purposes. A speaker of English has the opportunity to practice and optimize all the common accent sequences, even if one assumes that each tone needs to be practiced at several distinct strength levels. As a trivial example, if one counts combinations of ToBI symbols, treating ``H'', ``H*'', ``L'', ``L*'', ``!H'', and break as symbols, then there are only 216 possible trigram combinations and only 1296 possible 4-grams. A speaker could produce all of these 4-grams in an hour or two of speech, and will say the more common combinations every few minutes.

Greg Kochanski, Chilin Shih 2002-08-03