Teaching children to read using traditional picture books could set them up for dyslexia in later life.

That's the warning from a linguistics graduate who has published a doctorate into early learning techniques.

Pamela Protheroe said the use of picture books stunted imagination and left children over-dependent on associating images with words.

When the images were removed, children struggled to understand the meaning of the words.

Protheroe said children who only learned words with associated pictures ended up reading the words meaninglessly and used the picture to get the definition.

"Some children never grasp capturing the meaning in their head, they can only do it by looking at a picture."

Boys were more at risk from the use of picture books, and girls in New Zealand consistently outperformed boys in any test that involved language and literacy, she said.

"Literacy, more than any other area of learning, shows the biggest gender gap, and this gap is continuing to grow with boys falling further behind."

Boys have been identified as performing particularly poorly in literacy in New Zealand.

"When little boys are looking at pictures all the blood rushes to the visual centres rather than the linguistics centres."

A report in 2009 from the Organisation for Economic Co-operation and Development (OECD) confirmed that in 30 countries boys were lagging behind girls at secondary school with the gap greater in New Zealand than any other developed country, she said.

The majority of children were only moderately held back in their reading progress by the use of picture books, but children who were drawn to the pictures bore the brunt of the effects.

But children's bookseller, reviewer and book awards judge John McIntyre said Protheroe's theory was "arrant nonsense dressed in the cloak of academic research - and another case of boy-bashing".

McIntyre said boys were different to girls in many ways - and read differently. "Boys read for information, they read to work out their worlds, and they are expert at reading visually to discover what they need to know. Pictures lead them to the text, and to random discoveries that leads them to read more widely and deeply," he said.

Tests measuring literacy were mainly text-based and did not reflect the ability of boys to use visual literacy to access language.

Suggesting parents removed picture books from their children's bookshelves would be hugely damaging to national literacy, McIntyre said.

The Ministry of Education said it was not convinced that picture books were contributing to poor literacy rates for New Zealand children.

"In fact, research confirms the opposite. The importance of picture books and the development of visual language are critical to children's literacy skills and understanding in their early years," acting deputy secretary of student achievement Lesley Hoskin said.

"Children who have had high exposure to picture books are more likely to have wider and richer vocabulary, good understanding and comprehension of stories, and more developed alphabetic knowledge than children who have not had this exposure."