Representations and Computations in the Lexical System
In this project cognitive neuropsychological studies of brain-damaged patients reveal properties of the computational architecture and orthographic representations that underlie reading and spelling performance.
Representation of Letter Position in Spelling
The graphemic representations that underlie spelling performance must encode not only the identities of the letters in a word, but also the positions of the letters. In a recent study Simon Fischer-Baum, Brenda Rapp, and I investigated how letter position information is represented (Fischer-Baum, McCloskey, & Rapp, 2010). We presented evidence from two dysgraphic individuals, CM and LSS, who perseverate letters when spelling: that is, letters from previous spelling responses intrude into subsequent responses. The perseverated letters appear more often than expected by chance in the same position in the previous and subsequent responses. We used these errors to address the question of how letter position is represented in spelling. In a series of analyses we determined how often the perseveration errors produced maintain position as defined by a number of alternative theories of letter position encoding proposed in the literature. The analyses provide strong evidence that the grapheme representations used in spelling encode letter position such that position is represented in a graded manner based on distance from both edges of the word.
In current studies Simon Fischer-Baum and I are exploring position representations in reading, spoken word production, verbal short-term memory, and spatial short-term memory.
McCloskey, M., Macaruso, P., & Rapp, B. (2006). Grapheme-to-lexeme feedback in the spelling system: Evidence from a dysgraphic patient. Cognitive Neuropsychology, 23, 278-307.
Fischer-Baum, S., McCloskey, M., & Rapp, B. (2010). Representation of letter position in spelling: Evidence from acquired dysgraphia. Cognition, 115, 466-490.