Date of Award

8-2023

Document Type

Campus Access Thesis

Degree Name

Master of Science (MS)

Department

Developmental and Brain Sciences

First Advisor

Vivian Ciaramitaro

Second Advisor

Tashauna Blankenship

Third Advisor

Susan Zup

Abstract

The Bouba-Kiki (BK) effect is a crossmodal correspondence between abstract shapes and pseudowords in which round and sharp features of sounds are matched with round and sharp features of shapes, respectively. Previous research has found developmental changes in the BK effect, with weaker associations in 6-8 year-olds compared to older children and adults. We investigated two possible explanations for this developmental difference using 6-8, 9-11, and 18-65 year-olds. In a series of studies, we compared (1) changes in visual processing strategy and (2) changes in linguistic processing to the strength of the BK association, measured by the likelihood a participant matched a round or sharp shape with a round or sharp sound, respectively. First, we studied the potential influence of visual processing differences. Previous research suggests a shift from a local visual bias in children, in which they focus on the smaller elements that make up a larger image, to a global visual bias in adults, in which they focus on the image as a whole. Because adults may benefit from global processing to categorize the BK shapes as “sharp” or “round,” we hypothesized that a local to global shift could be driving the increasing strength of the BK association with age.

In the next study, to investigate sensitivity to phonological (speech sound) or orthographic (written letter) elements, we created pseudowords that differed on key phonological and orthographic features. We hypothesized that as we age and learn to read, orthographic knowledge bolsters sound-shape correspondences because orthographic curvature adds to the perceived “roundness” or “sharpness” of speech sounds.

While we did not find evidence supporting that changes in local and global visual processing are driving any changes in the strength of the BK association, we did find evidence that increasing sensitivity to certain linguistic elements is correlated with increasing BK association strength. We found that with age, participants have increases in sensitivity to orthographic and phonological differences. There was a significant increase in BK associations due to different consonants with age. There was no corresponding increase in BK associations based on different vowels, indicating that participants rely more on consonants than vowels to categorize a given sound as round or sharp. Furthermore, adults and older children showed a significant effect of consistency within a pseudoword. Internally consistent pseudowords, such as /mama/, (round consonant and round vowel), elicited stronger BK associations than inconsistent pseudowords, such as /mimi/, (round consonant and angular vowel). This suggests that younger children do not consider consonant-vowel consistency when choosing which shape best matches a sound, whereas adults and older children were more sensitive to congruency within a pseudoword. This increased sensitivity to phonological and orthographic elements may be driving by increasing literacy skills; we found that literacy is positively correlated with BK association strength independent of age. Our future work will examine if another visual processing skill may be related to the BK effect, such as visual attention development, and will explore the possibility that multilingualism may mediate the relationship between literacy and the BK effect.

Comments

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