How Incremental Is Language Production? Evidence from the Production of Utterances Requiring the Computation of Arithmetic Sums

The incremental approach to language production assumes that the production system interleaves planning and articulation processes. Two experiments examined this assumption. In the first, participants stated the sums of two two-digit numbers in one of three different kinds of utterances, the sum by itself, the sum followed by the sequence “is the answer,” or the frame “The answer is” followed by the sum. Problem difficulty was manipulated as well, so that in some conditions, speakers could (in principle) state the tens component of the sum while planning the ones. Latencies to begin to speak were the same for all three utterance types and were affected by the difficulty of the problem as a whole. Utterance durations were unaffected by problem difficulty. In the second experiment, participants were induced to speak incrementally through the use of a deadline procedure. Both latencies and utterance durations were influenced by the difficulty of the problem. This latter finding supports a basic premise of the incremental approach: Speakers sometimes speak and plan simultaneously. Nevertheless, the language production system appears not to be architecturally incremental; instead, the extent to which people speak incrementally is under strategic control.