Human Listeners Can Accurately Judge Strength and Height Relative to Self from Aggressive Roars and Speech

Abstract

Although animal vocalizations and human speech are known to communicate physical formidability, no previous study has examined whether human listeners can assess the strength or body size of vocalizers relative to their own, either from speech or from nonverbal vocalizations. Here, although men tended to underestimate women's formidability, and women to overestimate men's, listeners judged relative strength and height from aggressive roars and aggressive speech accurately. For example, when judging roars, male listeners accurately identified vocalizers who were substantially stronger than themselves in 88% of trials, and never as weaker. For male vocalizers only, roars functioned to exaggerate the expression of threat compared to aggressive speech, as men were rated as relatively stronger when producing roars. These results indicate that, like other mammals, the acoustic structure of human aggressive vocal signals (and in particular roars) may have been selected to communicate functional information relevant to listeners' survival.

Keywords: Behavioral Neuroscience; Neuroscience; Psychological Evolution.

Graphical abstract

Figure 1

Relative Strength Ratings as a Function of Actual Strength Differences Percentage of listeners judging vocalizers as relatively weaker (black), of similar strength (dark gray), or as relatively stronger (light gray) than themselves, as a function of the actual difference in strength between the listener and vocalizer. Separate graphs are reported for (A) male listeners rating male vocalizers, (B) female listeners rating male vocalizers, (C) male listeners rating female vocalizers, and (D) female listeners rating female vocalizers. Within each panel, for each actual strength difference category, separate bars are reported for listeners rating aggressive speech (left) and aggressive roars (right).

Figure 2

Relative Height Ratings as a Function of Actual Height Differences Percentage of listeners judging vocalizers as relatively shorter (black), of similar height (dark gray), or as relatively taller (light gray) than themselves, as a function of the actual difference in height between the listener and vocalizer. Separate graphs are reported for (A) male listeners rating male vocalizers, (B) female listeners rating male vocalizers, (C) male listeners rating female vocalizers, and (D) female listeners rating female vocalizers. Within each panel, for each actual height difference category, separate bars are reported for listeners rating aggressive speech (left) and aggressive roars (right).