Styles_IMRF2014_Psychoacoustic121_mini.pdf (426.41 kB)
Psychoacoustic correlates of speech-sound/shape/size mapping in a 121-alternative forced-choice task (Conference Poster)
Styles, SJ (2014). Psychoacoustic correlates of speech-sound/shape/size mapping in a 121-alternative forced-choice task. Poster presented at IMRF in June 2014, Amsterdam. (Full Poster).
Summary. While the ‘bouba/kiki’ effect (e.g., Ramachandran & Hubbard, 2011) is well known in the literature on sound/shape matching, there is limited systematic evidence about relationships between particular aspects of a shape’s outline and particular psychoacoustic features of spoken language. This study investigates the shape and size determinants of vowel matching, for four vowels tested across 121 different visual shapes, systematically controlled for size, and degree of edge curvature. Stimuli were presented in a grid where the vertical axis represented size, and the horizontal axis represented 11-steps of curvature (from a circle to a highly-curved shape, somewhat like an asterisk). Four vowels, representing the extremities of vowel space: /i/ /a/ /u/ and /y/ were tested in the 121AFC task.
Results. Consistent with findings since Sapir (1929), /a/ was matched to the largest shapes (p>.01). Consistent with findings since Köhler (1929), /u/ was matched to the roundest shapes (p>.01). By contrast, /i/ was matched to the smallest ‘pointiest’ shape (p>.01). These results demonstrate that size and roundness are mapped independently: size increases /i/>/u/>/a/, while roundness increases /i/>/a/>/u/. The fourth vowel /y/ is an interesting case: it shares articulatory features of height and frontness with /i/, but height and lip rounding with /u/. The response to /y/ fell close to /i/ and differed significantly from /u/ (p>.05). Thus, among the high vowels, vowel backness (correlated with F2) has more influence over speech-sound/roundness matching than does lip rounding (correlated with F3). The low vowel /a/ demonstrates that vowel height (correlated with F1) influences speech-sound/size matching.
Summary. While the ‘bouba/kiki’ effect (e.g., Ramachandran & Hubbard, 2011) is well known in the literature on sound/shape matching, there is limited systematic evidence about relationships between particular aspects of a shape’s outline and particular psychoacoustic features of spoken language. This study investigates the shape and size determinants of vowel matching, for four vowels tested across 121 different visual shapes, systematically controlled for size, and degree of edge curvature. Stimuli were presented in a grid where the vertical axis represented size, and the horizontal axis represented 11-steps of curvature (from a circle to a highly-curved shape, somewhat like an asterisk). Four vowels, representing the extremities of vowel space: /i/ /a/ /u/ and /y/ were tested in the 121AFC task.
Results. Consistent with findings since Sapir (1929), /a/ was matched to the largest shapes (p>.01). Consistent with findings since Köhler (1929), /u/ was matched to the roundest shapes (p>.01). By contrast, /i/ was matched to the smallest ‘pointiest’ shape (p>.01). These results demonstrate that size and roundness are mapped independently: size increases /i/>/u/>/a/, while roundness increases /i/>/a/>/u/. The fourth vowel /y/ is an interesting case: it shares articulatory features of height and frontness with /i/, but height and lip rounding with /u/. The response to /y/ fell close to /i/ and differed significantly from /u/ (p>.05). Thus, among the high vowels, vowel backness (correlated with F2) has more influence over speech-sound/roundness matching than does lip rounding (correlated with F3). The low vowel /a/ demonstrates that vowel height (correlated with F1) influences speech-sound/size matching.
