Our understanding of developmental dyslexia has progressed substantially in the past few decades. Once a contentious diagnosis, the understanding that dyslexia arises from a core phonological deﬁcit is now widely accepted. However, phonological awareness itself depends on cognitive processes such as sensory perception, short-term memory, long-term memory and executive function (Snowling, 2000). The associations between these skills and reading ability have been subject to intensive research, often fraught with debate. Most researched are sensory abilities. Proposed sensory causes of the phonological deﬁcit in developmental dyslexia include a magnocellular impairment in both the visual and auditory systems (e.g. Stein & Talcott, 1999); a general sensory processing deﬁcit (Ramus, 2003), a deﬁcit in cerebellar functioning (Nicolson et al., 1995) and deﬁcits in basic auditory temporal processing (Goswami et al., 2002; Tallal, 1980, 2004).1 Debate has been intensiﬁed by attempts to ﬁnd a ‘onedeﬁcit-ﬁts-all’ answer to reading difﬁculties. This is particularly true of research focusing on auditory perception and reading relationships: the focus of this chapter.
A ﬁrst hypothesis: the Rapid Auditory Processing Deﬁcit (RAPD)