Among the many challenges faced by children with dyslexia (and by their parents and teachers) is the nagging fear that their difficulties with reading are entirely hard-wired: predetermined by their genes and impossible to change. Recent research offers a balm for that fear. It suggests that experience plays a big role in dyslexia, both in exacerbating reading problems and, potentially, in easing them. Guinevere Eden, director of the Center for the Study of Learning at Georgetown University Medical Center, contends that dyslexia is not a problem of seeing, but a problem of processing language, of assembling individual sounds into words. Ms. Eden maintains that we should not be focusing on the visual system as we diagnose or treat dyslexia.