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. 2019 Mar 4;14(3):e0213034.
doi: 10.1371/journal.pone.0213034. eCollection 2019.

Human Roars Communicate Upper-Body Strength More Effectively Than Do Screams or Aggressive and Distressed Speech

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Free PMC article

Human Roars Communicate Upper-Body Strength More Effectively Than Do Screams or Aggressive and Distressed Speech

Jordan Raine et al. PLoS One. .
Free PMC article

Abstract

Despite widespread evidence that nonverbal components of human speech (e.g., voice pitch) communicate information about physical attributes of vocalizers and that listeners can judge traits such as strength and body size from speech, few studies have examined the communicative functions of human nonverbal vocalizations (such as roars, screams, grunts and laughs). Critically, no previous study has yet to examine the acoustic correlates of strength in nonverbal vocalisations, including roars, nor identified reliable vocal cues to strength in human speech. In addition to being less acoustically constrained than articulated speech, agonistic nonverbal vocalizations function primarily to express motivation and emotion, such as threat, and may therefore communicate strength and body size more effectively than speech. Here, we investigated acoustic cues to strength and size in roars compared to screams and speech sentences produced in both aggressive and distress contexts. Using playback experiments, we then tested whether listeners can reliably infer a vocalizer's actual strength and height from roars, screams, and valenced speech equivalents, and which acoustic features predicted listeners' judgments. While there were no consistent acoustic cues to strength in any vocal stimuli, listeners accurately judged inter-individual differences in strength, and did so most effectively from aggressive voice stimuli (roars and aggressive speech). In addition, listeners more accurately judged strength from roars than from aggressive speech. In contrast, listeners' judgments of height were most accurate for speech stimuli. These results support the prediction that vocalizers maximize impressions of physical strength in aggressive compared to distress contexts, and that inter-individual variation in strength may only be honestly communicated in vocalizations that function to communicate threat, particularly roars. Thus, in continuity with nonhuman mammals, the acoustic structure of human aggressive roars may have been selected to communicate, and to some extent exaggerate, functional cues to physical formidability.

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1
Spectrograms illustrating the acoustic structure of a typical (a) male roar, (b) male scream, (c) female roar, and (d) female scream. Note the higher F0 and more chaotic spectral structure of roars than screams.
Fig 2
Fig 2
Discriminant function analysis illustrating acoustic separation of voice conditions, (a) for all vocalizers, (b) for male vocalizers only, and (c) for female vocalizers only. Each data point represents the centroid of a vocal stimulus as a function of the first two discriminant variables that maximize individual separation. Larger black circles represent mean group centroids for each voice condition. The radar plot on the bottom right of panel (a) represents the loadings of the acoustic variables on the first two discriminant functions. Mean amplitude, amplitude variability, and amplitude modulation were the main factors separating voice conditions on the first function (DF1, Table A in S1 Tables). The second function (DF2, Table A in S1 Tables) relied mostly on F0 and harmonics-to-noise ratio. The pattern of separation was similar in male (b) and female (c) vocalizers.
Fig 3
Fig 3
Attributed strength as a function of actual strength, when listeners rated (a) male speech stimuli, (b) male vocalizations, (c) female speech stimuli, and (d) female vocalizations. Each data point represents the mean strength rating averaged across listeners attributed to each vocalization. Blue circles represent distress stimuli, red circles represent aggressive stimuli. Open circles represent speech stimuli, closed circles represent vocalizations. R2 values for each regression line are reported in the graphs. Removing the strongest female vocalizer from our analyzes did not affect the significance of our results.
Fig 4
Fig 4
Attributed height as a function of actual height, when listeners rated (a) male speech stimuli, (b) male vocalizations, (c) female speech stimuli, and (d) female vocalizations. Each data point represents the mean height rating averaged across listeners attributed to each vocalization. Blue circles represent distress stimuli, red circles represent aggressive stimuli. Open circles represent speech stimuli, closed circles represent vocalizations. R2 values for each regression line are reported in the graphs.

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References

    1. Andersson MB. Sexual selection. Princeton, NJ: Princeton University Press; 1994.
    1. Charlton BD, Zhihe Z, Snyder RJ. Giant pandas perceive and attend to formant frequency variation in male bleats. Anim Behav. 2010;79: 1221–1227. 10.1016/j.anbehav.2010.02.018 - DOI
    1. Charrier I, Ahonen H, Harcourt RG. What makes an Australian sea lion (Neophoca cinerea) male’s bark threatening? J Comp Psychol. 2011;125: 385–392. 10.1037/a0024513 - DOI - PubMed
    1. Pitcher BJ, Briefer EF, McElligott AG. Intrasexual selection drives sensitivity to pitch, formants and duration in the competitive calls of fallow bucks. BMC Evol Biol. 2015;15: 149 10.1186/s12862-015-0429-7 - DOI - PMC - PubMed
    1. Reby D, McComb K, Cargnelutti B, Darwin C, Fitch WT, Clutton-Brock T. Red deer stags use formants as assessment cues during intrasexual agonistic interactions. Proc R Soc Lond B Biol Sci. 2005;272: 941–947. 10.1098/rspb.2004.2954 - DOI - PMC - PubMed

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Grant support

This work was supported by the University of Sussex through a scholarship to J.R. Author K.P. was supported by the University of Lyon IDEXLYON project as part of the "Programme Investissements d’Avenir” (ANR-16-IDEX-0005), and by the European Commission through a Marie Skłodowska-Curie individual fellowship (H2020-MSCA-IF-2014-655859). The funders played no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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