The international longitudinal twin study has brought together researchers in Australia, the USA and Sweden to look at reading skills in 900 sets of twins.
Supplemented by pairs from the west Norwegian counties of Rogaland and Hordaland, these 1 800 children have been tested for reading and writing before and during their first three years in school.
The results show that the likelihood of developing early reading difficulties can often be explained by genetic rather than environmental factors.
That represents an important finding, according to Stefan Samuelsson, a Swedish adjunct professor at the University of Stavanger?s National Centre for Reading Education and Research.
His assessment is echoed by professors Brian Byrne at the University of New England in Australia and Richard Olson at the Colorado Learning Disabilities Research Centre in the USA.
- Earlier research has also shown that dyslexia and later reading difficulties among schoolchildren are influenced by genetic factors,? says Prof Samuelsson.
- Our idea was to involve twins before they started school to see how much of a role these hereditary factors play in learning to read and write.
The sets of twins who participated in the study were first tested for language and linguistic understanding when they were five. That was followed by tests at six, seven and eight.
This meant they were checked both before and after starting formal education in reading and writing at school.
- At the pre-school stage, we conducted psychological tests in addition to checks of vocabulary, word comprehension, rhyme and pronunciation, Prof Olson explains.
- As the twins got older, we extended this to cover reading, spelling, word groups and memory.
In addition, their parents were interviewed about the domestic environment, reports Prof Byrne, who launched the project in Sidney in 1999.
- We asked whether they had children?s books at home, visited the library, read to the children or were asked by the youngsters to read to them.
Finally, their teachers were questioned on how the twins performed in their lessons ? including whether they were attentive or hyperactive.
Using twins made it possible to compare children who came under different influences at home and in school with those who had identical backgrounds.
- Our findings show that children who get the same education and are influenced by the same environment don?t automatically become equally good at reading and writing, as one would wish, says Prof Samuelsson.
- The variation between good and poor readers after one year of school is still considerable. That?s not because the teachers do a poor job, but because hereditary plays a dominant role.
- Seventy per cent of this differential can be explained by genetic factors and 20 per cent by environmental influences.
He and his colleagues believe that the findings should not be interpreted to mean that being taught to read and write in schools is a waste of time.
- Instead, they indicate that such teaching is even more important than has previously been thought, observes Prof Olsen, who has worked with the Colorado reading project since 1979.
- Because genes play such a dominant role, good follow-up at school is crucial for children who have difficulties in reading and writing.
- To take another example, weight is influenced by genetics, but you can still eat healthily to avoid getting fat. Nurture plays an important role in encouraging people to stay slim.
A lot can be done for children with reading and writing problems, even though these usually reflect hereditary factors. But the earliest possible identification of sufferers is vital.
- The sooner you get started with learning to read and write, the better. At the same time, however, it?s never too late, says Prof Byrne.
- Parents can read aloud to their children at bedtime, and teachers can facilitate the reading of books at school, observes Prof Olsen.
- Much can be done if the adults simply take the time for it. These children read more slowly than others, so grown-ups must be more patient.
Focusing attention on reading and writing difficulties is also important from a social perspective, Prof Samuelsson notes.
- Literacy is a must in our modern society. To receive an education, you have to know the alphabet and understand words. This is the key that opens most of society?s doors.
A lot can be done for children who have problems learning to read and write, even though a study of twins has shown that such difficulties are usually due to hereditary factors.
Text: Silje Stangeland
Photo: Dag Magne Søyland