The overall goal of the research we conduct is to understand how people understand spoken language. One of the pre-requisites to understanding a sentence is identifying the words that compose the sentence. The recognition of a spoken word is more complex than it appears. A chunk of the spoken signal has to be matched with one of the 100,000 words that an adult knows. Because speech is a continuous, highly complex, and rapidly changing signal, processing must occur as soon as acoustic information becomes available and in an incremental fashion.
Incremental processing is rendered difficult by the fact that the interpretation of an incomplete fragment of speech is almost always ambiguous. Consider the word candle. By the end of the fragment can, possible interpretations include candle, but also candy, canvas, can, etc. Thus, the listener must perform incremental interpretation of the speech signal in the face of substantial ambiguity.