Social evaluative implications of sensory adaptation to human voices.

People form social evaluations of others following brief exposure to their voices, and these impressions are calibrated based on recent perceptual experience. Participants adapted to voices with fundamental frequency (f o; the acoustic correlate of perceptual pitch) manipulated to be gender-typical (i.e. masculine men and feminine women) or gender-atypical (i.e. feminine men and masculine women) before evaluating unaltered test voices within the same sex. Adaptation resulted in contrastive aftereffects. Listening to gender-atypical voices caused female voices to sound more feminine and attractive (Study 1) and male voices to sound more masculine and attractive (Study 2). Studies 3a and 3b tested whether adaptation occurred on a conceptual or perceptual level, respectively. In Study 3a, perceivers adapted to gender-typical or gender-atypical voices for both men and women (i.e. adaptors pitch manipulated in opposite directions for men and women) before evaluating unaltered test voices. Findings showed weak evidence that evaluations differed between conditions. In Study 3b, perceivers adapted to masculinized or feminized voices for both men and women (i.e. adaptors pitch manipulated in the same direction for men and women) before evaluating unaltered test voices. In the feminized condition, participants rated male targets as more masculine and attractive. Conversely, in the masculinized condition, participants rated female targets as more feminine and attractive. Voices appear to be evaluated according to gender norms that are updated based on perceptual experience as well as conceptual knowledge.

The role of loudness in vocal intimidation.

Across many species, a major function of vocal communication is to convey formidability, with low voice frequencies traditionally considered the main vehicle for projecting large size and aggression. Vocal loudness is often ignored, yet it might explain some puzzling exceptions to this frequency code. Here we demonstrate, through acoustic analyses of over 3,000 human vocalizations and four perceptual experiments, that vocalizers produce low frequencies when attempting to sound large, but loudness is prioritized for displays of strength and aggression. Our results show that, although being loud is effective for signaling strength and aggression, it poses a physiological trade-off with low frequencies because a loud voice is achieved by elevating pitch and opening the mouth wide into a-like vowels. This may explain why aggressive vocalizations are often high-pitched and why open vowels are considered "large" in sound symbolism despite their high first formant. Callers often compensate by adding vocal harshness (nonlinear vocal phenomena) to undesirably high-pitched loud vocalizations, but a combination of low and loud remains an honest predictor of both perceived and actual physical formidability. The proposed notion of a loudness-frequency trade-off thus adds a new dimension to the widely accepted frequency code and requires a fundamental rethinking of the evolutionary forces shaping the form of acoustic signals. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Laughter and culture.

Like most human non-verbal vocalizations, laughter is produced by speakers of all languages, across all known societies. But despite this obvious fact (or perhaps because of it), there is little comparative research examining the structural and functional similarity of laughter across speakers from different cultures. Here, we describe existing research examining (i) the perception of laughter across disparate cultures, (ii) conversation analysis examining how laughter manifests itself during discourse across different languages, and (iii) computational methods developed for automatically detecting laughter in spoken language databases. Together, these three areas of investigation provide clues regarding universals and cultural variations in laughter production and perception, and offer methodological tools that can be useful for future large-scale cross-cultural studies. We conclude by providing suggestions for areas of research and predictions of what we should expect to discover. Overall, we highlight how important questions regarding human vocal communication across cultures can be addressed through the examination of spontaneous and volitional laughter. This article is part of the theme issue 'Cracking the laugh code: laughter through the lens of biology, psychology and neuroscience'.

Signals and cues of social groups.

A crucial factor in how we perceive social groups involves the signals and cues emitted by them. Groups signal various properties of their constitution through coordinated behaviors across sensory modalities, influencing receivers' judgments of the group and subsequent interactions. We argue that group communication is a necessary component of a comprehensive computational theory of social groups.

Vocal communication across cultures: theoretical and methodological issues.

The study of human vocal communication has been conducted primarily in Western, educated, industrialized, rich, democratic (WEIRD) societies. Recently, cross-cultural investigations in several domains of voice research have been expanding into more diverse populations. Theoretically, it is important to understand how universals and cultural variations interact in vocal production and perception, but cross-cultural voice research presents many methodological challenges. Experimental methods typically used in WEIRD societies are often not possible to implement in many populations such as rural, small-scale societies. Moreover, theoretical and methodological issues are often unnecessarily intertwined. Here, I focus on three areas of cross-cultural voice modulation research: (i) vocal signalling of formidability and dominance, (ii) vocal emotions, and (iii) production and perception of infant-directed speech. Research in these specific areas illustrates challenges that apply more generally across the human behavioural sciences but also reveals promise as we develop our understanding of the evolution of human communication. This article is part of the theme issue 'Voice modulation: from origin and mechanism to social impact (Part II)'.

Toward a productive evolutionary understanding of music.

We discuss approaches to the study of the evolution of music (sect. R1); challenges to each of the two theories of the origins of music presented in the companion target articles (sect. R2); future directions for testing them (sect. R3); and priorities for better understanding the nature of music (sect. R4).

Recognizing affiliation in colaughter and cospeech.

Theories of vocal signalling in humans typically only consider communication within the interactive group and ignore intergroup dynamics. Recent work has found that colaughter generated between pairs of people in conversation can afford accurate judgements of affiliation across widely disparate cultures, and the acoustic features that listeners use to make these judgements are linked to speaker arousal. But to what extent does colaughter inform third party listeners beyond other dynamic information between interlocutors such as overlapping talk? We presented listeners with short segments (1-3 s) of colaughter and simultaneous speech (i.e. cospeech) taken from natural conversations between established friends and newly acquainted strangers. Participants judged whether the pairs of interactants in the segments were friends or strangers. Colaughter afforded more accurate judgements of affiliation than did cospeech, despite cospeech being over twice in duration relative to colaughter on average. Sped-up versions of colaughter and cospeech (proxies of speaker arousal) did not improve accuracy for either identifying friends or strangers, but faster versions of both modes increased the likelihood of tokens being judged as being between friends. Overall, results are consistent with research showing that laughter is well suited to transmit rich information about social relationships to third party overhearers-a signal that works between, and not just within conversational groups.

Body synchrony in triadic interaction.

Humans subtly synchronize body movement during face-to-face conversation. In this context, bodily synchrony has been linked to affiliation and social bonding, task success and comprehension, and potential conflict. Almost all studies of conversational synchrony involve dyads, and relatively less is known about the structure of synchrony in groups larger than two. We conducted an optic flow analysis of body movement in triads engaged in face-to-face conversation, and explored a common measure of synchrony: time-aligned bodily covariation. We correlated this measure of synchrony with a diverse set of covariates related to the outcome of interactions. Triads showed higher maximum cross-correlation relative to a surrogate baseline, and 'meta-synchrony', in that composite dyads in a triad tended to show correlated structure. A windowed analysis also revealed that synchrony varies widely across an interaction. As in prior studies, average synchrony was low but statistically reliable in just a few minutes of interaction. In an exploratory analysis, we investigated the potential function of body synchrony by predicting it from various covariates, such as linguistic style matching, liking, laughter and cooperative play in a behavioural economic game. Exploratory results do not reveal a clear function for synchrony, though colaughter within triads was associated with greater body synchrony, and is consistent with an earlier analysis showing a positive connection between colaughter and cooperation. We end by discussing the importance of expanding and codifying analyses of synchrony and assessing its function.

Origins of music in credible signaling.

Music comprises a diverse category of cognitive phenomena that likely represent both the effects of psychological adaptations that are specific to music (e.g., rhythmic entrainment) and the effects of adaptations for non-musical functions (e.g., auditory scene analysis). How did music evolve? Here, we show that prevailing views on the evolution of music - that music is a byproduct of other evolved faculties, evolved for social bonding, or evolved to signal mate quality - are incomplete or wrong. We argue instead that music evolved as a credible signal in at least two contexts: coalitional interactions and infant care. Specifically, we propose that (1) the production and reception of coordinated, entrained rhythmic displays is a co-evolved system for credibly signaling coalition strength, size, and coordination ability; and (2) the production and reception of infant-directed song is a co-evolved system for credibly signaling parental attention to secondarily altricial infants. These proposals, supported by interdisciplinary evidence, suggest that basic features of music, such as melody and rhythm, result from adaptations in the proper domain of human music. The adaptations provide a foundation for the cultural evolution of music in its actual domain, yielding the diversity of musical forms and musical behaviors found worldwide.

Sound context modulates perceived vocal emotion.

Many animal vocalizations contain nonlinear acoustic phenomena as a consequence of physiological arousal. In humans, nonlinear features are processed early in the auditory system, and are used to efficiently detect alarm calls and other urgent signals. Yet, high-level emotional and semantic contextual factors likely guide the perception and evaluation of roughness features in vocal sounds. Here we examined the relationship between perceived vocal arousal and auditory context. We presented listeners with nonverbal vocalizations (yells of a single vowel) at varying levels of portrayed vocal arousal, in two musical contexts (clean guitar, distorted guitar) and one non-musical context (modulated noise). As predicted, vocalizations with higher levels of portrayed vocal arousal were judged as more negative and more emotionally aroused than the same voices produced with low vocal arousal. Moreover, both the perceived valence and emotional arousal of vocalizations were significantly affected by both musical and non-musical contexts. These results show the importance of auditory context in judging emotional arousal and valence in voices and music, and suggest that nonlinear features in music are processed similarly to communicative vocal signals.

Publisher Correction: Five-month-old infants detect affiliation in colaughter.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Five-month-old infants detect affiliation in colaughter.

Colaughter-simultaneous laughter between two or more individuals-allows listeners across different cultures and languages to quickly evaluate affiliation within a social group. We examined whether infants are sensitive to acoustic information in colaughter that indicates affiliation, specifically whether they can differentiate colaughter between friends and colaughter between strangers. In the first experiment, infants who heard alternating trials of colaughter between friends and strangers listened longer to colaughter between friends. In the second experiment, we examined whether infants were sensitive to the social context that was appropriate for each type of colaughter. Infants heard colaughter between friends and colaughter between strangers preceded by a silent visual scene depicting one of two different social contexts: either two people affiliating or turning away from each other. Infants looked longer when the social scene was incongruent with the type of colaughter. By 5 months, infants preferentially listen to colaughter between friends and detect when colaughter does not match the valence of a social interaction. The ability to rapidly evaluate acoustic features in colaughter that reveal social relationships between novel individuals appears early in human infancy and might be the product of an adaptive affiliation detection system that uses vocal cues.

The Perception of Spontaneous and Volitional Laughter Across 21 Societies.

Laughter is a nonverbal vocalization occurring in every known culture, ubiquitous across all forms of human social interaction. Here, we examined whether listeners around the world, irrespective of their own native language and culture, can distinguish between spontaneous laughter and volitional laughter-laugh types likely generated by different vocal-production systems. Using a set of 36 recorded laughs produced by female English speakers in tests involving 884 participants from 21 societies across six regions of the world, we asked listeners to determine whether each laugh was real or fake, and listeners differentiated between the two laugh types with an accuracy of 56% to 69%. Acoustic analysis revealed that sound features associated with arousal in vocal production predicted listeners' judgments fairly uniformly across societies. These results demonstrate high consistency across cultures in laughter judgments, underscoring the potential importance of nonverbal vocal communicative phenomena in human affiliation and cooperation.

General trust impedes perception of self-reported primary psychopathy in thin slices of social interaction.

Little is known about people's ability to detect subclinical psychopathy from others' quotidian social behavior, or about the correlates of variation in this ability. This study sought to address these questions using a thin slice personality judgment paradigm. We presented 108 undergraduate judges (70.4% female) with 1.5 minute video thin slices of zero-acquaintance triadic conversations among other undergraduates (targets: n = 105, 57.1% female). Judges completed self-report measures of general trust, caution, and empathy. Target individuals had completed the Levenson Self-Report Psychopathy (LSRP) scale. Judges viewed the videos in one of three conditions: complete audio, silent, or audio from which semantic content had been removed using low-pass filtering. Using a novel other-rating version of the LSRP, judges' ratings of targets' primary psychopathy levels were significantly positively associated with targets' self-reports, but only in the complete audio condition. Judge general trust and target LSRP interacted, such that judges higher in general trust made less accurate judgments with respect to targets higher in primary and total psychopathy. Results are consistent with a scenario in which psychopathic traits are maintained in human populations by negative frequency dependent selection operating through the costs of detecting psychopathy in others.

Fathers' Infant-Directed Speech in a Small-Scale Society.

When speaking to infants, mothers often alter their speech compared to how they speak to adults, but findings for fathers are mixed. This study examined interactions (N = 30) between fathers and infants (Mage  ± SD = 7.8 ± 4.3 months) in a small-scale society in Vanuatu and two urban societies in North America. Fundamental frequency (F0 ) and speech rate were measured in infant-directed and adult-directed speech. When speaking to infants, fathers in both groups increased their F0 range, yet only Vanuatu fathers increased their average F0 . Conversely, North American fathers slowed down their speech rate to infants, whereas Vanuatu fathers did not. Behavioral traits can vary across distant cultures while still potentially solving similar communicative problems.

Three-month-old human infants use vocal cues of body size.

Differences in vocal fundamental (F0) and average formant (Fn) frequencies covary with body size in most terrestrial mammals, such that larger organisms tend to produce lower frequency sounds than smaller organisms, both between species and also across different sex and life-stage morphs within species. Here we examined whether three-month-old human infants are sensitive to the relationship between body size and sound frequencies. Using a violation-of-expectation paradigm, we found that infants looked longer at stimuli inconsistent with the relationship-that is, a smaller organism producing lower frequency sounds, and a larger organism producing higher frequency sounds-than at stimuli that were consistent with it. This effect was stronger for fundamental frequency than it was for average formant frequency. These results suggest that by three months of age, human infants are already sensitive to the biologically relevant covariation between vocalization frequencies and visual cues to body size. This ability may be a consequence of developmental adaptations for building a phenotype capable of identifying and representing an organism's size, sex and life-stage.

Detecting affiliation in colaughter across 24 societies.

Laughter is a nonverbal vocal expression that often communicates positive affect and cooperative intent in humans. Temporally coincident laughter occurring within groups is a potentially rich cue of affiliation to overhearers. We examined listeners' judgments of affiliation based on brief, decontextualized instances of colaughter between either established friends or recently acquainted strangers. In a sample of 966 participants from 24 societies, people reliably distinguished friends from strangers with an accuracy of 53-67%. Acoustic analyses of the individual laughter segments revealed that, across cultures, listeners' judgments were consistently predicted by voicing dynamics, suggesting perceptual sensitivity to emotionally triggered spontaneous production. Colaughter affords rapid and accurate appraisals of affiliation that transcend cultural and linguistic boundaries, and may constitute a universal means of signaling cooperative relationships.

The evolution of coordinated vocalizations before language.

Ackermann et al. briefly point out the potential significance of coordinated vocal behavior in the dual pathway model of acoustic communication. Rhythmically entrained and articulated pre-linguistic vocal activity in early hominins might have set the evolutionary stage for later refinements that manifest in modern humans as language-based conversational turn-taking, joint music-making, and other behaviors associated with prosociality.

If looks could kill: anger attributions are intensified by affordances for doing harm.

Emotion perception is necessarily imprecise, leading to possible overperception or underperception of a given emotion extant in a target individual. When the costs of these two types of errors are recurrently asymmetrical, categorization mechanisms can be expected to be biased to commit the less costly error. Contextual factors can influence this asymmetry, resulting in a concomitant increase in biases in the perception of a given emotion. Anger motivates aggression, hence an important contextual factor in anger perception is the capacity of the perceived individual to inflict harm. The greater the capacity to harm, the more costly it is to underestimate the extent to which the target is angry, and therefore the more that perception should be biased in favor of overestimation. Consonant with this prediction, in two studies, U.S. adults perceived greater anger when models were holding household objects having affordances as weapons (e.g., garden shears) than when they were holding objects lacking such affordances (e.g., a watering can) or were empty-handed. Consistent with the unique relationship between anger and aggression, this positive bias did not appear in judgments of other negative emotions.