Planning intonation under cognitive constraints of speaking

Pitch peaks tend to be higher at the beginning of longer utterances than in shorter ones (e.g., 'The Santa is decorating the Christmas trees' vs. 'The Santa is decorating the Christmas tree and the window'). Given that a rise in pitch frequently occurs in response to increased mental effort, we explore the link between higher pitch at the beginning of an utterance and the cognitive demands of sentence planning for speech production. To modulate the cognitive resources available for generating a message in a visual world speech production task, the study implemented a dual-task paradigm. Participants described pictures depicting events with multiple actors. In one-half of these descriptions, the participants memorized three nouns, later recalling them and answering related questions. The results demonstrate both cognitive and linguistic influences on sentence intonation. Specifically, intonation peaks at the beginning of longer utterances were higher than in shorter ones, and they were lower under the condition of memory load than under no load. Measurements of eye gaze indicated a very short processing delay at the outset of processing the picture and the sentence, which was rapidly overcome by the start of speech. The short time frame of restricted cognitive resources thus was manifested in the lowering of the intonation peaks. These findings establish a novel link between language-related memory span and sentence intonation and warrant further study to investigate the cognitive mechanisms of the planning of intonation.