A number of factors can cause reading difficulties:

• immature oral language knowledge or 'psycholinguistic knowledge'. This can occur in a range of areas such as
• specific delay in the development of language,
• difficulty in learning knowledge about the sound properties of language, that is, phonological or phonemic processing,
• a difficulty due to the recall of knowledge from memory, and in particular, the names of items, that is rapid automatised naming or RAN,
• grammatical knowledge
• short term auditory memory and
• vocabulary
• a difficulty learning and storing alphanumeric and other visual symbolic codes, the types of symbolic codes that constitute written language.
• thinking, reasoning (that is, 'cognitive') and information processing factors such as
  • using an analytic-sequential thinking or learning preference,
  • memory abilities,
  • the amount of information person can handle,
  • the types of relationships individuals can see between ideas.
• sensory, perceptual processing impairment, and in particular
  • visual sensory abilities and
  • auditory sensory abilities.
• emotional factors such as
  • a lack of self concept,
  • anxiety when reading and
  • depression in learning context.
  This factor is measured initially by analysing attitudes to reading.

These explanations are shown in the following diagram:

It is usually not possible to infer these causes directly from reading patterns.