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Vocal-tract resonances as indexical cues in rhesus monkeys.

Ghazanfar AA, Turesson HK, Maier JX, van Dinther R, Patterson RD, Logothetis NK - Curr. Biol. (2007)

Bottom Line: Formants play an important role in human communication, helping us not only to distinguish several different speech sounds [1], but also to extract important information related to the physical characteristics of the speaker, so-called indexical cues.How did formants come to play such an important role in human vocal communication?One hypothesis suggests that the ancestral role of formant perception--a role that might be present in extant nonhuman primates--was to provide indexical cues [2-5].

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany. asifg@princeton.edu

ABSTRACT
Vocal-tract resonances (or formants) are acoustic signatures in the voice and are related to the shape and length of the vocal tract. Formants play an important role in human communication, helping us not only to distinguish several different speech sounds [1], but also to extract important information related to the physical characteristics of the speaker, so-called indexical cues. How did formants come to play such an important role in human vocal communication? One hypothesis suggests that the ancestral role of formant perception--a role that might be present in extant nonhuman primates--was to provide indexical cues [2-5]. Although formants are present in the acoustic structure of vowel-like calls of monkeys [3-8] and implicated in the discrimination of call types [8-10], it is not known whether they use this feature to extract indexical cues. Here, we investigate whether rhesus monkeys can use the formant structure in their "coo" calls to assess the age-related body size of conspecifics. Using a preferential-looking paradigm [11, 12] and synthetic coo calls in which formant structure simulated an adult/large- or juvenile/small-sounding individual, we demonstrate that untrained monkeys attend to formant cues and link large-sounding coos to large faces and small-sounding coos to small faces-in essence, they can, like humans [13], use formants as indicators of age-related body size.

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Monkeys Match the Acoustic Size Extracted from Formant Frequencies to the Matching Face(A) The mean percentage of total looking time spent looking at the matching video display; the dotted line indicates chance expectation (n = 24). Error bars represent the standard error of the mean.(B) A significant proportion of subjects looked longer at the match than the nonmatch screen.
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fig2: Monkeys Match the Acoustic Size Extracted from Formant Frequencies to the Matching Face(A) The mean percentage of total looking time spent looking at the matching video display; the dotted line indicates chance expectation (n = 24). Error bars represent the standard error of the mean.(B) A significant proportion of subjects looked longer at the match than the nonmatch screen.

Mentions: Monkeys looked at the matching screen for 58.4% of the total time they spent looking at either screen (match: 13.08 ± 1.45 s; nonmatch: 10.26 ± 1.49 s); this proportion differed significantly from chance [one-sample t test, t(23) = 2.67, p = 0.014] (Figure 2A). This ∼3 s difference, although seemingly small, is robust in the context of the preferential-looking method and is similar to differences reported for similar experiments in both humans [31, 32] and monkeys [11, 12]. With the percentage of total looking time to the match screen used as a dependent variable, an ANOVA was conducted to explore any possible interactions among four primary variables (side of screen [left versus right], vocalizer [acoustic signal of monkey 1 versus monkey 2], face [visual signal of monkey 1 versus monkey 2], and vocal tract length [long versus short]). All main effects or interactions were nonsignificant. Thus, there were no response biases toward the left or right screen, the stimulus exemplars (the calls or the faces used), or the size of the monkey on the matching screen (e.g., monkeys did not look longer overall when the matching screen showed a large monkey). Nineteen out of twenty-four monkeys in the present experiment preferentially attended to the dynamic face that best matched the body size simulated by the coo vocalization played through the speaker (Figure 2B, sign test, p = 0.003). These results demonstrate that rhesus monkeys can, without any training whatsoever, use formant structure to assess the age-related body size of conspecific individuals.


Vocal-tract resonances as indexical cues in rhesus monkeys.

Ghazanfar AA, Turesson HK, Maier JX, van Dinther R, Patterson RD, Logothetis NK - Curr. Biol. (2007)

Monkeys Match the Acoustic Size Extracted from Formant Frequencies to the Matching Face(A) The mean percentage of total looking time spent looking at the matching video display; the dotted line indicates chance expectation (n = 24). Error bars represent the standard error of the mean.(B) A significant proportion of subjects looked longer at the match than the nonmatch screen.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2361420&req=5

fig2: Monkeys Match the Acoustic Size Extracted from Formant Frequencies to the Matching Face(A) The mean percentage of total looking time spent looking at the matching video display; the dotted line indicates chance expectation (n = 24). Error bars represent the standard error of the mean.(B) A significant proportion of subjects looked longer at the match than the nonmatch screen.
Mentions: Monkeys looked at the matching screen for 58.4% of the total time they spent looking at either screen (match: 13.08 ± 1.45 s; nonmatch: 10.26 ± 1.49 s); this proportion differed significantly from chance [one-sample t test, t(23) = 2.67, p = 0.014] (Figure 2A). This ∼3 s difference, although seemingly small, is robust in the context of the preferential-looking method and is similar to differences reported for similar experiments in both humans [31, 32] and monkeys [11, 12]. With the percentage of total looking time to the match screen used as a dependent variable, an ANOVA was conducted to explore any possible interactions among four primary variables (side of screen [left versus right], vocalizer [acoustic signal of monkey 1 versus monkey 2], face [visual signal of monkey 1 versus monkey 2], and vocal tract length [long versus short]). All main effects or interactions were nonsignificant. Thus, there were no response biases toward the left or right screen, the stimulus exemplars (the calls or the faces used), or the size of the monkey on the matching screen (e.g., monkeys did not look longer overall when the matching screen showed a large monkey). Nineteen out of twenty-four monkeys in the present experiment preferentially attended to the dynamic face that best matched the body size simulated by the coo vocalization played through the speaker (Figure 2B, sign test, p = 0.003). These results demonstrate that rhesus monkeys can, without any training whatsoever, use formant structure to assess the age-related body size of conspecific individuals.

Bottom Line: Formants play an important role in human communication, helping us not only to distinguish several different speech sounds [1], but also to extract important information related to the physical characteristics of the speaker, so-called indexical cues.How did formants come to play such an important role in human vocal communication?One hypothesis suggests that the ancestral role of formant perception--a role that might be present in extant nonhuman primates--was to provide indexical cues [2-5].

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany. asifg@princeton.edu

ABSTRACT
Vocal-tract resonances (or formants) are acoustic signatures in the voice and are related to the shape and length of the vocal tract. Formants play an important role in human communication, helping us not only to distinguish several different speech sounds [1], but also to extract important information related to the physical characteristics of the speaker, so-called indexical cues. How did formants come to play such an important role in human vocal communication? One hypothesis suggests that the ancestral role of formant perception--a role that might be present in extant nonhuman primates--was to provide indexical cues [2-5]. Although formants are present in the acoustic structure of vowel-like calls of monkeys [3-8] and implicated in the discrimination of call types [8-10], it is not known whether they use this feature to extract indexical cues. Here, we investigate whether rhesus monkeys can use the formant structure in their "coo" calls to assess the age-related body size of conspecifics. Using a preferential-looking paradigm [11, 12] and synthetic coo calls in which formant structure simulated an adult/large- or juvenile/small-sounding individual, we demonstrate that untrained monkeys attend to formant cues and link large-sounding coos to large faces and small-sounding coos to small faces-in essence, they can, like humans [13], use formants as indicators of age-related body size.

Show MeSH
Related in: MedlinePlus