In this way, dyslexia as a term becomes related to intelligence. This means that reading difficulties combined with normal intelligence is termed dyslexia, while reading difficulties with low intelligence is not termed dyslexia. From this understanding, we get different definitions of dyslexia, such as this one for instance:
A disorder manifested by a difficulty in learning to read despite conventional instruction, adequate intelligence and socio-cultural opportunity. It is dependent upon fundamental cognitive difficulties which are frequently of a constitutional character. (World Federation of Neurology, 1968).
Such definitions have been criticised. That’s because problems with word decoding / reading words have appeared to be the primary problem in dyslexia, and that these difficulties do not necessarily correlate with intelligence. Several researchers have pointed out that intelligence is a factor which is unsuitable for predicting reading development.