Different behavioral and eye movement patterns of dyslexic readers with and without attentional deficits during single word reading.

Comorbidity of learning disabilities is a very common phenomenon which is intensively studied in genetics, neuropsychology, prevalence studies and causal deficit research. In studies on the behavioral manifestation of learning disabilities, however, comorbidity is often neglected. In the present study, we systematically examined the reading behavior of German-speaking children with dyslexia, of children with attentional problems, of children with comorbid dyslexia and attentional problems and of normally developing children by measuring their reading accuracy, naming latencies and eye movement patterns during single word reading. We manipulated word difficulty by contrasting (1) short vs. long words with (2) either low or high sublexical complexity (indexed by consonant cluster density). Children with dyslexia only (DYS) showed the expected reading fluency impairment of poor readers in regular orthographies but no accuracy problem. In contrast, comorbid children (DYS+AD) had significantly higher error rates than all other groups, but less of a problem with reading fluency than DYS. Concurrently recorded eye movement measures revealed that DYS made the highest number of fixations, but exhibited shorter mean single fixations than DYS+AD. Word length had the strongest effect on dyslexic children, whereas consonant cluster density affected all groups equally. Theoretical implications of these behavioral and eye movement patterns are discussed and the necessity for controlling for comorbid attentional deficits in children with reading deficits is highlighted.

Welcome to the real world: validating fixation-related brain potentials for ecologically valid settings.

Exploration of the real world usually expresses itself through a perceptual behaviour that is complex and adaptive -- an interplay between external visual and internal cognitive states. However, up to now, the measurement of electrophysiological correlates of cognitive processes has been limited to situations, in which the experimental setting confined visual exploration to the mere reception of a strict serial order of events. Here we show -- exemplified by the well known old/new effect in the domain of visual word recognition -- that an alternative approach that utilizes brain potentials corresponding to eye fixations during free exploration reveals effects as reliable as conventional event-related brain potentials.