Dyslexics' Visual Attention Field

Evaluation of the Visuo-attention Field of Symbols Versus Objects Visual Search in Dyslexic Subjects. DyslexiaSPOTLIGHT

dyslexia is often considered like a phonological deficit but some researches show that a visual attention (V-A) deficit can occur in dyslexia. The investigator want to show that some dyslexics have a reduced V-A field in visual search when the investigator use separable feature (letter-like). If the investigator demonstrate that, he will show that V-A deficit can be transpose to an ability acquired before reading, the visual search. Therefore, the V-A deficit can't be a consequence of reading problem but a cause of it for some dyslexics. The investigator could imagine an earlier diagnosis for children at risk to develop dyslexia and make reeducation more specific for the deficit observed.

Visual attention span : the subject see a 5 letters strings during 200 ms and he has to report it orally whatever the order Visual search : the subject has to find a target among distractors (24 or 48) in different conditions of stimuli (conjunction feature or separable feature) and different conditions of view (full view or reduced view with the moving window paradigm) Elementary visuo spatial perception: the subject passes 6 visuo spatial tests to judge his visuo spatial abilities. All of these tests will be made during an unique visit of 1h30.

Visual attention span : the subject see a 5 letters strings during 200 ms and he has to report it verbally whatever the order Visual search : the subject has to find a target among distractors (24 or 48) in different conditions of stimuli (conjunction feature or separable feature) and different conditions of view (full view or reduced view with the moving window paradigm) Elementary visuo spatial perception: the subject passes 6 visuo spatial test to judge his visuo spatial abilities. "test de l'alouette" : reading test during 3 minutes, we note the number of word read and the errors. We obtain lexical age. All of these tests will be made during an unique visit of 1h30.

Respond time in visual search in different condition of view (full view or reduced view) with separable feature.

The subject will have to find a target among distractors, when he will find it, he will have to push a button and we will have his respond time. We will compare the respond time in two view condition: the participant will see all the visual scene or he will have reduced visible window so he won't see all the scene, the periphery will be hide and he will have to move his sight to show it.

The subject will have to find a target among distractors, when he will find it, he will have to push a button and we will collect his respond time. We compare the respond time between two number of distractors (24 or 48)

with an eye tracker the investigator will analyze the ocular movements during visual search (saccades and fixations) and the equip will compare the visual behavior between the different groups and the different conditions.

the investigator will test with different exercises the elementary visuo spatial perception of the participant and he will compare between groups and also he will make correlation with the respond time in visual search.

the subject have to report orally a 5 letters' string presented during 200 ms, the investigator could see if a correlation exist between VAS and RT, VAS and visual exploration, VAS and visuo spatial perception.

Inclusion Criteria: normal or corrected to normal vision diagnosed dyslexics with a recent "alouette" test Exclusion Criteria: other developmental problem (dysphasia, dyspraxia, ADHD) strabismus, amblyopia, oculomotor paralysis