Voice pitch is the perceptual correlate of fundamental frequency (F0) that describes how high or low a voice sounds. People differ in their habitual pitch level, but they can also modulate their voice to sound higher or lower in pitch. Research has shown that when men's F0 is manipulated to a lower value, they are perceived to be more likely to win physical fights than when their F0 is manipulated to a higher level. However, it remains unclear i) why lower pitch enhances men's perceived chance of winning fights (i.e., what the signal communicates) and ii) how this dominance signal could remain honest (i.e., how the correlation between signal intensity and whatever information it sends is maintained when the temptation to cheat is strong).

Drawing on the retaliation-cost model, an influential model of animal communication, it is hypothesized that men's voice pitch influences their perceived likelihood of winning fights because it signals their aggressive intent and the honesty of the signal is maintained by a retaliation cost (i.e., men who modulate their pitch to a lower level risk physical confrontation from other men). If this hypothesis is correct, men who lower their pitch to address an offender in a conflict situation will be perceived more likely to aggress (H1), which will in turn predict their perceived likelihood to win a fight should it occur (H2). Further, if pitch modulation is a signal specifically designed to communicate men's aggressive intent, it should influence men's perceived aggressive intent independently of their condition (e.g., physical strength) (H3). Finally, men who use lower pitch in a competitive situation will be more likely than men who use higher pitch to elicit aggressive responses from other men---especially those who are physically strong and/or high in trait competitiveness ( H4). Experiment Set 1 tested and supported H1-3, and Experiment Set 2 supported H4. However, as a further test of H4, Experiment Set 3 showed a reverse pattern in terms of the effect of pitch level. The implications of these four sets of experiments regarding the retaliation cost model, research on men's pitch, and human aggression were discussed.