Speech perception engages at least two linguistic systems: the phonetic system, which extracts discrete sound units from acoustic input, and the phonological system, which combines these units to form individual words. Previously, researchers generally believed that dyslexia was caused by phonological impairment, but results from the current study, led by Iris Berent of Northeastern University in Boston, suggest that the phonetic system may actually be the cause.
"Our findings confirm that dyslexia indeed compromises the language system, but the locus of the deficit is in the phonetic, not the phonological system, as had been previously assumed", says Berent.
In the study, Hebrew-speaking college students had difficulty discriminating between similar speech sounds, but had no problem tracking abstract phonological patterns, even for novel words, suggesting that the phonological system is intact but the phonetic system is compromised.
"Our research demonstrates that a closer analysis of the language system can radically alter our understanding of the disorder, and ultimately, its treatment," says Berent.