Effects of Encouraging the Use of Gestures on Speech.

Purpose Previous studies have investigated the effects of the inability to produce hand gestures on speakers' prosodic features of speech; however, the potential effects of encouraging speakers to gesture have received less attention, especially in naturalistic settings. This study aims at investigating the effects of encouraging the production of hand gestures on the following speech correlates: speech discourse length (number of words and discourse length in seconds), disfluencies (filled pauses, self-corrections, repetitions, insertions, interruptions, speech rate), and prosodic properties (measures of fundamental frequency [F0] and intensity). Method Twenty native Italian speakers took part in a narration task in which they had to describe the content of short comic strips to a confederate listener in 1 of the following 2 conditions: (a) nonencouraging condition (N), that is, no instructions about gesturing were given, and (b) encouraging condition (E), that is, the participants were instructed to gesture while telling the story. Results Instructing speakers to gesture led effectively to higher gesture rate and salience. Significant differences were found for (a) discourse length (e.g., the narratives had more words in E than in N) and (b) acoustic measures (F0 maximum, maximum intensity, and mean intensity metrics were higher in E than in N). Conclusion The study shows that asking speakers to use their hands while describing a story can have an effect on narration length and can also impact on F0 and intensity metrics. By showing that enhancing the gesture stream could affect speech prosody, this study provides further evidence that gestures and prosody interact in the process of speech production.