Date of Award

5-16-2025

Document Type

Thesis

First Advisor

Ilaria Berteletti

Second Advisor

James Waller

Abstract

This capstone project investigated the prevalence and manifestation of synesthesia—a perceptual condition where stimulation in one sensory pathway triggers automatic, involuntary experiences in another—within d/Deaf, hard-of-hearing (DHH), and sign language user populations. Despite an estimated prevalence of over 4% in the general population and findings that many synesthetic experiences are language-based, little is known about how synesthesia presents across different language modalities, including signed languages. This project explored the phenomenon in two phases: an initial online survey assessing the prevalence and characteristics of synesthesia among DHH and signing individuals and follow-up interviews with self-reported synesthetes along with a test-retest procedure to examine the reliability of their reported associations. The goal was to determine whether synesthesia is tied specifically to spoken language or can also emerge through visual-spatial languages like ASL. The project also considered how sign language structure may influence synesthetic experiences. Results show that the two experimental participants did not demonstrate consistent language-color associations, while one control participant did for written letters. Survey data estimated a 3.26% prevalence among the signing population—slightly below the general population. Interview findings suggested that for signers, emotion, context, and meaning may play a more significant role in triggering synesthetic experiences than phonological or graphemic form, raising methodological questions for future research.

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