Differential sensitivity to vowel continua in Old World monkeys (Macaca) and humans

Abstract

Previous studies indicate that monkey pure tone frequency discrimination is quantitatively and qualitatively very different from that of humans: Monkey DLs at 1.0 and 2.0 kHz are up to 20 times larger than human DLs, and monkeys DLs increase as sensation level increases, in contrast to human DLs [Sinnott et al., J. Acoust. Soc. Am. 78, 1977-1985 (1985); Sinnott et al., J. Comp. Psychol. 101, 126-131 (1987)]. These results led to an hypothesis that monkey frequency discrimination is more dependent upon "rate" coding than is that of humans. The present study compared monkey and human DLs for formant frequency changes along three synthetic vowel continua /I-i/, /ae-epsilon/, and /a-v/. Here, monkey DLs for formants near 1.0 and 2.0 kHz (32-48 Hz) were only about two to three times larger than human DLs (11-21 Hz), and both monkeys and humans exhibited relatively similar, flat sensation level functions. Taken together, these data indicate that monkey and human frequency discrimination is more similar in the case of a complex vowel stimulus than in the case of a simple pure tone stimulus. Results are discussed in relation to "rate" versus "temporal" coding of tones and vowels in the auditory system.

Cues to body size in the formant spacing of male koala (Phascolarctos cinereus) bellows: honesty in an exaggerated trait

“…Indeed, numerous other non-human animals spontaneously respond to formant shifts in their own species-typical vocalisations (Fitch and Kelley, 2000;Reby et al, 2005;Fitch and Fritz, 2006;Charlton et al, 2007a;Charlton et al, 2008;Charlton et al, 2010; and are capable of perceiving formant shifts in human speech sounds with a high degree of accuracy (Baru, 1975;Burdick and Miller, 1975;Hienz et al, 1981;Hienz and Brady, 1988;Sinnott, 1989;Dooling and Brown, 1990;Sinnott and Kreiter, 1991;Sommers et al, 1992;Hienz et al, 1996). It is also noteworthy that the inter-individual variation in formant spacing we report is high: the minimum and maximum formant frequency spacing values for the exhalation, initial inhalation and later inhalation phases of bellows corresponded to a 16%, 25% and 31% variation around the mean values of 796, 708 and 354Hz, respectively (see Table1).…”

Spectral integration plasticity in cat auditory cortex induced by perceptual training

“…Psychophysical studies in humans and animals have investigated the spectral processing of broadband stimuli with parametrically varied spectral envelopes, especially formant position and modulation depth (e.g. Pick 1980;Festen & Plomp 1981;Yost 1982;van Veen & Houtgast, 1985;Shamma et al, 1992;Bernstein & Green 1987;Hillier and Miller, 1991;Sommer et al, 1992;Sinnott et al, 1976;Sinnott and Kreiter, 1991;Supin et al, 1994;Amagai et al, 1999;O'Connor et al, 2000). However, no attempt had been made to link psychophysical measurements with neurophysiological properties of cortical neurons.…”

Encoding of vowel-like sounds in the auditory nerve: Model predictions of discrimination performance

“…Estimating the ability of the auditory system to resolve changes in formant frequency is a first step in understanding speech processing in the auditory system. Psychophysical experiments have estimated formant-frequency discrimination ability (Flanagan, 1955;Mermelstein, 1978;Sinnott and Kreiter, 1991;KewleyPort and Watson, 1994); however, reported thresholds of the formant-frequency discrimination tasks have differed among studies because of the complexity of the stimuli and differences in experimental procedures. For example, Mermelstein (1978) found that the threshold for discriminating changes in the first formant at 350 Hz was 50 Hz, which is much higher than the result of Flanagan (1955), who reported discrimination thresholds for the first formant (at 300 Hz) of 12 to 17 Hz.…”