Lifting the curtain on the Wizard of Oz: Biased voice-based impressions of speaker size.

Abstract

The consistent, but often wrong, impressions people form of the size of unseen speakers are not random but rather point to a consistent misattribution bias, one that the advertising, broadcasting, and entertainment industries also routinely exploit. The authors report 3 experiments examining the perceptual basis of this bias. The results indicate that, under controlled experimental conditions, listeners can make relative size distinctions between male speakers using reliable cues carried in voice formant frequencies (resonant frequencies, or timbre) but that this ability can be perturbed by discordant voice fundamental frequency (F-sub-0, or pitch) differences between speakers. The authors introduce 3 accounts for the perceptual pull that voice F-sub-0 can exert on our routine (mis)attributions of speaker size and consider the role that voice F-sub-0 plays in additional voice-based attributions that may or may not be reliable but that have clear size connotations.

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

“…Because pitch and formant differences correspond to different kinds of body size differences within and between organisms [7][8][9][10][11][12][13][14], it was also of theoretical interest to conduct an analysis broken up by the type of frequency manipulation infants were exposed to. This allowed us to verify that both types of manipulations produced a similar pattern to that found in the combined analysis, and to look for any differences in the magnitude of the looking time effects they produced ( particularly because the pitch stimuli differences were slightly larger than those in the formant conditions).…”

“…Because both pitch and formants independently predict body size across a variety of species, and in humans distinguish sex and age morphs [10,11], these results open up the interesting possibility that developmental adaptations are taking advantage of acoustic invariances, and do so in order to help infants learn about the attributes of conspecifics in the environment, including differences in their age, sex, and size [50]. This finding opens up three new directions for future research: (i) exploring the relative contributions of fundamental and formant frequencies in judgments of other differences between organisms, such as differences in dominance and formidability [4,16,22], (ii) more precisely determining if this size/sound expectation reflects expectations about different species, different age and sex morphs within a species, and/or expectations of size differences within these morphs, and (iii) assessing the ecological and taxonomic distribution of this competence by exploring if and when similar representations develop in non-human animal species, particularly in species that differ in the range of body size differences they encounter in their natural ecology.…”

“…For example, lowering of F n and/or F 0 in dog barks increases attributions of the dog's aggressiveness in human listeners [20]. Playback studies with male deer vocalizations also show that male deer perceive the experimental lowering of F n and F 0 as more threatening ( [21]; see also [9,11,16,22,23] for more extensive reviews). Adult domestic dogs also correctly match the growls of larger versus smaller dogs onto visual cues of dog body size [24].…”

“…Pitch negatively correlates with the thickness and length of the vocal folds, which is due primarily to exposure to male secondary sexual hormones at puberty, particularly testosterone [15]. Consequently, much of the variation in pitch and formants in mammalian vocalizations, including in humans, is due to size differences between sex and age body morphs, and to hormone-induced secondary sexual maturation divergence at puberty [10,11].…”

“…Previous experimental evidence demonstrates that human adults are sensitive to these relationships, even within age and sex morphs [11,[16][17][18]. For instance, experimentally lowering F 0 and formant dispersion in young men's voices increases the speaker's perceived masculinity, size and age [19].…”