Analyzing the influence of deafness on serial position function for letters.

Previous research has shown that letter and digit identification typically follows a W-shaped serial position function, whereas symbol identification exhibits an inverted U-shaped pattern. Given that reading outcomes vary widely among deaf populations, the present study investigated whether deaf adults display serial position functions similar to hearing adults. Using the Target-in-String Identification paradigm, we compared letter, digit, and symbol recognition across five target positions in matched groups of deaf and hearing participants. Both groups demonstrated a pronounced first-letter advantage, consistent with specialized position-tuned letter detectors. However, only the hearing group showed the canonical W-shaped function for letters. Deaf participants exhibited a more linear and quadratic profile, with reduced accuracy at central positions, which may be consistent with a potentially greater influence of visual crowding, even within foveal vision. No reliable position effects emerged for symbols, and both groups displayed similar linear position effects for digits. These findings indicate that while initial-letter prioritization is preserved in deaf readers, spatial tuning for other positions may be influenced, partially supporting the MRF theory and underscoring the need for models that account for variability in orthographic processing across populations.