[Experimental study of response latency of visual search processes and premotor decision latency in dyslexic and non-dyslexic children. Model of linear regression: derived parametric estimates].

BACKGROUND

For some time the question of a visual impairment in dyslexic children has been a source of controversy in the literature. Depending on the method used, the findings point either to receptor or neural impairment or to a visual deficit in information processing. The question remains of whether these findings mask retardation in the motor planning and execution of a response.

METHOD

In this investigation 61 children (15 dyslexic boys and 15 dyslexic girls aged 8 years 0 months to 10 years 8 months and 16 non-dyslexic boys and 15 non-dyslexic girls aged 8 years 0 months to 10 years 10 months) were tested using a computer-assisted visual display method (visual scan procedure). The results were included into a linear regression model.

RESULTS

Compared to the non-dyslexic children the dyslexic children had a significant retardation in the speed of motor response (MANCOVA, Mann-Whitney U-test). For the "pure" visual process no differences in time course were found. Another important findings is the surprisingly wide range of results obtained for individual dyslexic children. In some instances there were deviations as great as 3.6 sigma (SEM). These findings indicate that we may be dealing with an individual partial impairment. It should be noted that the calculation of the linear regression model cannot be detailed for the group of dyslexic children. The prerequisites for a linear regression model are not satisfied. The comparability of the results is therefore limited.

CONCLUSIONS

We cannot assume there will be a manifest visuomotor impairment in all dyslexic children when the stimulus is presented at the center and periphery of the field of vision. However, if such an impairment is present it is highly likely that the findings contain a mixture of retardation of pre-motor and visual decision latency. This would have substantial consequences for therapy, as visuomotor perception training would not be indicated in all instances. Some dyslexic children, both boys and girls, achieve completely "normal" results.