The complexity of English spelling makes it the most difficult European language for dyslexics, according to new research.
Dundee University's literacy research group found that children classed as dyslexic in some countries would be considered adequate readers in English.
The group is working with the Dyslexia Institute to investigate how dyslexia can be treated most effectively. It is also collaborating with European researchers, with the aid of a £250,000 grant from the Economic and Social Research Council and the Leverhulme Trust.
Its founder, Philip Seymour, said: "Initial comparisons of the reading and spelling problems suffered by dyslexics in these European countries show that dyslexics who learn to read in English have a particularly difficult time."
Most European languages have a "shallow orthography" in which letters correspond to sounds in a regular and consistent way. English was the most extreme in departing from this, Professor Seymour said.
His work suggests that children need to be able to follow two distinct processes when learning to read English. The first, the alphabetic, involves working out pronunciation on the basis of individual letters, making even a nonsense word such as "plind" perfectly readable. The second, lexical, pathway involves recognising words as entities, such as "yacht", which is very irregular.
The most popular theory was that dyslexia stemmed from the child having difficulty dividing words into phonemic components, but some had problems with the lexical process of recognising familiar words, Professor Seymour said.
The existence of the two pathways might give rise to different types of dyslexia in English. This is less obvious in other languages because the alphabetic and lexical pathways correspond.