An experimental test of the relationship between voice intonation and persuasion in the domain of health

Abstract

Objective: In the process of behaviour change, intonation of speech is an important aspect that may influence persuasion when auditory messages are used. In two experiments, we tested to what extent different levels of intonation are related to persuasion and whether for some recipients the threat posed by the message information might become too strong to face.

Design: In Study 1, 130 respondents listened to a health message with either a low, moderate or high level of intonation. In Study 2 (N = 143), the same manipulations of intonation were applied but half of the respondents were affirmed before they listened to the persuasive message. Intention to increase fruit and vegetable intake was used as a dependent variable.

Results: Both studies showed that high intonation led to a significant drop in intention among respondents who perceived their own health as good. After self-affirmation, persuasion was increased.

Conclusion: A high level of intonation seems to induce self-regulatory defences in people who do not see the necessity to change their health behaviour, whereas people with poor perceived health might perceive potential to change. The use of a normal level of intonation in auditory health messages is recommended.

Keywords:

• persuasion
• speech
• self-affirmation
• fruit and vegetable consumption

Acknowledgement

We would like to thank Elsemiek van Vendeloo for her contribution to the data collection for Study 2.

Funding

This work was supported by the Netherlands Organization for Health Research and Development (ZonMW) [grant number 121020021].

Notes

1. Besides the manipulation of intonation, speech rate was as well manipulated in this study (slow, moderate and fast). Adding speech rate as a between-subjects factor to the model (including interaction term) did not affect the findings of manipulated intonation on perceived voice characteristics. In addition, no significant main effects of speech rate were found on perceived intonation and voice pitch (p > .05), except for perceived speech rate; F (2, 121) = 93.92, p < .001, η² = .61. The means showed a linear pattern as predicted with significant contrasts. The manipulation of speech rate did not have additional value in the context of the presented manipulation check.

2. The model was also tested with speech rate as additional factor. The three-way interaction was not significant (p = .35), neither was the two-way interaction between speech rate and perceived health status (p = .86), suggesting that speech rate was redundant. Speech rate did affect the findings of manipulated intonation: the interaction between intonation and perceived health status became marginally significant after including speech rate (p = .055) and the effect of intonation in people who perceived their own health as good was not significant (p = .20).