The male voice: an evolutionary perspective

The introduction to this thesis outlines the evolutionary theory of human mating behaviour and describes the process of vocal production and auditory perception in humans. In addition it provides a brief overview of some of the research studies examining the role of vocalisations in courtship and competitive behaviours in animals. The body of this thesis is then divided into three parts. Part 1 examined whether male vocal frequencies may be an honest signal of physical attributes such as body size, body shape and hormonal quality. Results of Study 1 found that fundamental frequency but not formant dispersion was related to age. The voices of younger (but post-pubertal) males had lower fundamental frequency. Furthermore, fundamental frequency was significantly negatively associated with shoulder and chest circumferences, shoulder-hip-ratio and body weight. A significant negative relationship was also found between formant dispersion and both weight and height and some measures of body shape. Study 2a and 2b then found evidence of a relationship between fundamental frequency and circulating testosterone in adult males with some evidence for diurnal variation in fundamental frequency (reflecting alterations in testosterone). Some limited evidence of a relationship between formant dispersion and circulating testosterone was also found. No relationship between prenatal testosterone or cortisol and vocal frequencies was observed. The second part of this thesis explored the role of the male voice in both inter and intra sexual selection. Study 3 examined perceptions of male voices by male listeners. Results revealed that the judgements made by male listeners concerning the age and physique of male speakers were broadly consistent with the relationships observed between physical characteristics and vocal frequencies in Study 1. Results also suggested that formant frequencies and not fundamental frequency indicate the dominance of a speaker but that both vocal parameters inform judgements that male listeners make about the attractiveness of male speakers to females. Study 4 examined perceptions of male voices by female listeners. Results suggest that both fundamental and formant frequencies influence judgements of attractiveness and dominance. In addition the relationship between visual and vocal attractiveness and dominance was examined. No relationship was observed between visual and vocal attractiveness although there was a significant relationship between visual and vocal dominance. The final section of this thesis examined the relative importance of the voice in comparison to the face within the context of attraction and dominance. Results of two studies suggest that vocal and visual attractiveness and dominance may not be related and that the relative importance of facial and vocal cues depends upon the judgement being made. The face appears to have a greater influence on attractiveness judgements but the voice appears to have a greater influence on judgements of dominance. The results of the studies reported in this thesis are discussed in relation to the findings of other researchers in the field which together provide evidence that the five criteria for sexual selection of communication signals (Snowden, 2004) are met by the deep voice of the human male. Furthermore, I speculate that the evolution of low fundamental frequencies and low formant