A multiple case study was conducted in order to assess three leading theories of developmental dyslexia: (i) the phonological theory, (ii) the magnocellular (auditory and visual) theory and (iii) the cerebellar theory. Sixteen dyslexic and 16 control university students were administered a full battery of psychometric, phonological, auditory, visual and cerebellar tests. Individual data reveal that all 16 dyslexics suffer from a phonological deficit, 10 from an auditory deficit, four from a motor deficit and two from a visual magnocellular deficit. Results suggest that a phonological deficit can appear in the absence of any other sensory or motor disorder, and is sufficient to cause a literacy impairment, as demonstrated by five of the dyslexics. Auditory disorders, when present, aggravate the phonological deficit, hence the literacy impairment. However, auditory deficits cannot be characterized simply as rapid auditory processing problems, as would be predicted by the magnocellular theory. Nor are they restricted to speech. Contrary to the cerebellar theory, we find little support for the notion that motor impairments, when found, have a cerebellar origin or reflect an automaticity deficit. Overall, the present data support the phonological theory of dyslexia, while acknowledging the presence of additional sensory and motor disorders in certain individuals.

Spoken languages have been classified by linguists according to their rhythmic properties, and psycholinguists have relied on this classification to account for infants' capacity to discriminate languages. Although researchers have measured many speech signal properties, they have failed to identify reliable acoustic characteristics for language classes. This paper presents instrumental measurements based on a consonant/vowel segmentation for eight languages. The measurements suggest that intuitive rhythm types reflect specific phonological properties, which in turn are signaled by the acoustic/phonetic properties of speech. The data support the notion of rhythm classes and also allow the simulation of infant language discrimination, consistent with the hypothesis that newborns rely on a coarse segmentation of speech. A hypothesis is proposed regarding the role of rhythm perception in language acquisition.

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We review a series of experiments aimed at understanding the nature of the phonological deficit in developmental dyslexia. These experiments investigate input and output phonological representations, phonological grammar, foreign speech perception and production, and unconscious speech processing and lexical access. Our results converge on the observation that the phonological representations of people with dyslexia may be intact, and that the phonological deficit surfaces only as a function of certain task requirements, notably short-term memory, conscious awareness, and time constraints. In an attempt to reformulate those task requirements more economically, we propose that individuals with dyslexia have a deficit in access to phonological representations. We discuss the explanatory power of this concept and we speculate that a similar notion might also adequately describe the nature of other associated cognitive deficits when present.

14Centre référent pour le diagnostic des troubles du langage et des apprentissages, Département de pédiatrie, CHU Nord, Grenoble, France; Background: The relationship between phoneme awareness, rapid automatized naming (RAN), verbal short-term/working memory (ST/WM) and diagnostic category is investigated in control and dyslexic children, and the extent to which this depends on orthographic complexity. Methods: General cognitive, phonological and literacy skills were tested in 1,138 control and 1,114 dyslexic children speaking six different languages spanning a large range of orthographic complexity (Finnish, Hungarian, German, Dutch, French, English). Results: Phoneme deletion and RAN were strong concurrent predictors of developmental dyslexia, while verbal ST/WM and general verbal abilities played a comparatively minor role. In logistic regression models, more participants were classified correctly when orthography was more complex. The impact of phoneme deletion and RAN-digits was stronger in complex than in less complex orthographies. Conclusions: Findings are largely consistent with the literature on predictors of dyslexia and literacy skills, while uniquely demonstrating how orthographic complexity exacerbates some symptoms of dyslexia.

An on-going debate surrounds the relationship between specific language impairment and developmental dyslexia, in particular with respect to their phonological abilities. Are these distinct disorders? To what extent do they overlap? Which cognitive and linguistic profiles correspond to specific language impairment, dyslexia and comorbid cases? At least three different models have been proposed: the severity model, the additional deficit model and the component model. We address this issue by comparing children with specific language impairment only, those with dyslexia-only, those with specific language impairment and dyslexia and those with no impairment, using a broad test battery of language skills. We find that specific language impairment and dyslexia do not always co-occur, and that some children with specific language impairment do not have a phonological deficit. Using factor analysis, we find that language abilities across the four groups of children have at least three independent sources of variance: one for non-phonological language skills and two for distinct sets of phonological abilities (which we term phonological skills versus phonological representations). Furthermore, children with specific language impairment and dyslexia show partly distinct profiles of phonological deficit along these two dimensions. We conclude that a multiple-component model of language abilities best explains the relationship between specific language impairment and dyslexia and the different profiles of impairment that are observed.

Spoken languages have been classified by linguists according to their rhythmic properties, and psycholinguists have relied on this classification to account for infants' capacity to discriminate languages. Although researchers have measured many speech signal properties, they have failed to identify reliable acoustic characteristics for language classes. This paper presents instrumental measurements based on a consonant/vowel segmentation for eight languages. The measurements suggest that intuitive rhythm types reflect specific phonological properties, which in turn are signaled by the acoustic/phonetic properties of speech. The data support the notion of rhythm classes and also allow the simulation of infant language discrimination, consistent with the hypothesis that newborns rely on a coarse segmentation of speech. A hypothesis is proposed regarding the role of rhythm perception in language acquisition.

Humans, but no other animal, make meaningful use of spoken language. What is unclear, however, is whether this capacity depends on a unique constellation of perceptual and neurobiological mechanisms, or whether a subset of such mechanisms are shared with other organisms. To explore this problem, we conducted parallel experiments on human newborns and cotton-top tamarin monkeys to assess their ability to discriminate unfamiliar languages. Using a habituation-dishabituation procedure, we show that human newborns and tamarins can discriminate sentences from Dutch and Japanese, but not if the sentences are played backwards. Moreover, the cues for discrimination are not present in backward speech. This suggests that the human newborns' tuning to certain properties of speech relies on general processes of the primate auditory system.A fundamental question in the study of language evolution and acquisition is the extent to which humans are innately endowed with specialized capacities to comprehend and produce speech. Theoretical arguments have been used to argue that language acquisition must be based on an innately specified language faculty (1, 2), but the precise nature and extent of this "language organ" is mainly an empirical matter, which notably requires studies of human newborns as well as non-human animals (3-5). With respect to studies of humans, we already know that newborns as young as four days old have the capacity to discriminate phonemes categorically (6) and perceive well-formed syllables as units (7-9); they are sensitive to the rhythm of speech, as shown in experiments where newborns distinguish sentences from languages that have different rhythmic properties, but not from languages that share the same rhythmic structure (10, 11); however newborns don't discriminate languages when speech is played backwards (10), and neurophysiological studies suggest that both infants and adults process natural speech differently from backwards speech (12, 13). All of these studies indicate that humans are born with capacities that facilitate language acquisition, and that seem well attuned to the properties of speech. Studies of non-human animals, however, show that some of these capacities may predate our hominid origins. For example, insects, birds, non-primate mammals, and primates process their own, species-typical Correspondence should be addressed to Franck Ramus. E-mail: f.ramus@ucl.ac.uk. Present address: Institute of Cognitive Neuroscience, 17 Queen Square, London WC1N 3AR, GB. sounds in a categorical manner, and some of these species perceive speech categorically (14-18).Our aim in this paper is to extend the comparative study of speech perception in three directions. First, we have conducted joint experiments on human newborns and on monkeys using the same design and the same material. Second, whereas most studies of non-human animal speech perception involve extensive training prior to testing on a generalization task, our experimental approach -the habituationdishabituation paradigm -involves no traini...