Reading and Writing: An Interdisciplinary Journal 11: 213–237, 1999.
© 1999 Kluwer Academic Publishers. Printed in the Netherlands.
Biological constraints on literacy acquisition
Servizio di Neuropsichiatria Infantile, University of Parma, Italy
Abstract. This paper investigates some of the biological constraints that shape the process of
literacy acquisition. It explores the possibility of isolating processing components of reading
which correspond to computational units of equivalent size in the neural architecture. After
reviewing and evaluating the current approaches to the biology of literacy acquisition, the
paper considers three interconnected topics: (a) developmental dissociations, (b) early stages
of literacy acquisition (in a transparent orthography), and (c) effects of remedial interven-
tion for children with reading disorders. Developmental dissociations between reading and
severe mental retardation, motor impairment, congenital anarthria and inaccuracy in phonemic
awareness tasks reveal the functional independence of the reading processes. The early stages
of literacy acquisition in a transparent orthography show a very steep increase in word and non-
word reading accuracy; a speed that could hardly be accounted for by unconstrained learning.
Finally, rehabilitation treatments of reading disorders either produce no speciﬁc effects, or
marginal improvements in reading accuracy, which fade away in the long term. Concurrently,
these data suggest that the process of literacy acquisition is largely constrained by a spe-
ciﬁc biological architecture which mimics the functional properties of a modular system. It
is speculated that the core component of reading is a metaphonological parser, designed to
perform automatic cross-modal associations between visual and sublexical units, according
to the paradigms set up by any orthographic system. The phylogenetic implications of the
‘speciﬁcity hypothesis’ are discussed.
Keywords: Literacy acquisition, Dyslexia, Brain and reading, Modularity
In November 1896, Pringle Morgan published a brief note in the British Med-
ical Journal, documenting the ﬁrst case of developmental dyslexia (in one
sense of that multiply ambiguous term). A 14-year-old boy, intelligent and
quick at games, had failed to acquire even the rudimentary skills of reading,
in spite of seven years’ effort, at school and with special tutoring. Morgan’s
account of the developmental disorders of reading was straightforward: the
young boy was affected by ‘word blindness, evidently congenital and due
most probably to defective development of that region of the brain, disease
of which in adults produces practically the same symptom, that is, the left
angular gyrus’ (Morgan 1896).