Left visual field bias during face perception aligns with individual differences in reading skills and is absent in dyslexia.

BACKGROUND: When looking at faces, we tend to attend more to the left visual field (corresponding to the right side of the person's face). This phenomenon is called the left visual field bias (LVF) and is presumed to reflect the brain's right-sided dominance for face processing. Whether alterations in hemispheric dominance are present in dyslexia, and are linked with individual differences in word reading development more generally, is still unclear, and no prior research has utilized gaze-based LVF bias to explore these topics. AIMS: The aim of the study was to examine whether the LVF bias differs in dyslexia and to examine the association with word-reading skills assessed dimensionally. SAMPLE: Forty-six 9-13 year-old children with dyslexia and community control children, matched on age and listening comprehension. METHODS: Participants were presented with a recorded face on a screen while their gaze patterns were collected with an eye tracker. Fixations to the left versus the right side of the face stimuli were compared. RESULTS: Results showed a clear LVF bias in community controls, while no such bias was seen in the dyslexic group. Moreover, the strength of the LVF bias was correlated with better word reading in the controls. CONCLUSIONS: Our results suggest a link between weakened hemispheric dominance for face processing in dyslexia and in poor word reading, at least to the extent that the LVF bias actually mirrors underlying physiology. We discuss the implications of these novel findings, highlighting the need for future research to determine the specificity and developmental sources of LVF bias alterations.

Face Processing in School Children with Dyslexia: Neuropsychological and Eye-tracking Findings.

Dyslexia is a neurodevelopmental difficulty affecting reading, but recent data in adults suggest that difficulties also extend to face processing. Here, we tested face processing in school children with and without dyslexia, using eye-tracking and neuropsychological tests. Children with dyslexia didn't differ significantly from controls in face gaze patterns, face memory, or face identification accuracy. However, they were slower and more heterogeneous, with larger within-group variance than controls. Increased gaze patterns toward the eyes were associated with better face memory in controls. We discuss the possible role of experiential factors in prior research linking dyslexia and face processing differences.

Facial speech processing in children with and without dyslexia.

What role does the presence of facial speech play for children with dyslexia? Current literature proposes two distinctive claims. One claim states that children with dyslexia make less use of visual information from the mouth during speech processing due to a deficit in recruitment of audiovisual areas. An opposing claim suggests that children with dyslexia are in fact reliant on such information in order to compensate for auditory/phonological impairments. The current paper aims at directly testing these contrasting hypotheses (here referred to as "mouth insensitivity" versus "mouth reliance") in school-age children with and without dyslexia, matched on age and listening comprehension. Using eye tracking, in Study 1, we examined how children look at the mouth across conditions varying in speech processing demands. The results did not indicate significant group differences in looking at the mouth. However, correlation analyses suggest potentially important distinctions within the dyslexia group: those children with dyslexia who are better readers attended more to the mouth while presented with a person's face in a phonologically demanding condition. In Study 2, we examined whether the presence of facial speech cues is functionally beneficial when a child is encoding written words. The results indicated lack of overall group differences on the task, although those with less severe reading problems in the dyslexia group were more accurate when reading words that were presented with articulatory facial speech cues. Collectively, our results suggest that children with dyslexia differ in their "mouth reliance" versus "mouth insensitivity," a profile that seems to be related to the severity of their reading problems.

Syllable Repetition vs. Finger Tapping: Aspects of Motor Timing in 100 Healthy Adults.

In this study we systematically compared syllable repetition and finger tapping in healthy adults, and explored possible impacts of tempi, metronome, musical experience, and age on motor timing ability. One hundred healthy adults used finger-tapping and syllable repetition to perform an isochronous pulse in three different tempi, with and without a metronome. Results showed that the motor timing was more accurate with finger tapping than with syllable repetition in the slowest tempo, and the motor timing ability was better with the metronome than without. Persons with musical experience showed better motor timing accuracy than persons without such experience, and the timing asynchrony increased with increasing age. The slowest tempo 90 bpm posed extra challenges to the participants. We speculate that this pattern reflects the fact that the slow tempo lies outside the 3-8 Hz syllable rate of natural speech, which in turn has been linked to theta-based oscillations in the brain.