Resumen de Sensitivity to temporal synchrony and selective attention in audiovisual speech in infants at risk for autism: A longitudinal study
The detection of temporal synchrony is thought to play a fundamental role in the development of socio-communicative skills, with special emphasis in language acquisition. In typical development, this perceptual ability develops in the first year of life, tightly coupled with developmental changes in infants’ ability to selectively attend to different parts of a talker’s face.
Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder primarily defined on the basis of socio-communicative deficit, frequently entailing language impairments. Given the high heritability of the disorder, these atypicalities are present not only in individuals with ASD but usually extend to some first-degree relatives, such as infants at risk for autism by virtue of having an older diagnosed sibling. According to some current theoretical approaches of the emergency of ASD, primary early perceptual and attentional atypicalities would underlie later impairments in higher-order socio-communicative abilities associated to the disorder. On the basis of one very specific theoretical hypothesis (namely, the Intersensory Impairment Hypothesis), in this thesis it is predicted that infants at high-risk for ASD would show early atypicalities in both the detection of temporal synchrony and the pattern of selective attention when processing audiovisual speaking faces.
Thus, this dissertation addresses two research questions. First, it aims to explore if infants at high-risk for autism spectrum disorder (ASD) show a reduced sensitivity to temporal synchrony in the context of audiovisual speaking faces in the first year of life when compared to low-risk infants. Secondly, it aims to examine whether, across this same period of development, high-risk infants differ from low-risk controls in the pattern of changes in selective attention to facial features when they explore talking faces. To tackle these two questions, a longitudinal study was conducted to follow the trajectories of the two groups in these two skills at 4, 8 and 12 months of age. By using a preferential looking task, we presented high-risk and low-risk infants with two audiovisual speaking faces uttering a story, one in synchrony an one temporarily misaligned. Selective attention was also measured during the task in the two groups by recording infants’ eye‐gaze to the talker's eyes and mouth.
The results of this preliminary study showed that, contrary to what was expected, high-risk infants succeeded in detecting temporal synchrony in a comparable way to low-risk controls. By contrast, groups followed different patterns of shifts in the selective attention to facial features across time. Whereas low-risk infants shifted their pattern of preference to the eyes and the mouth across the first year of life and selectively focused on the mouth from the second half of the first year of life onwards, high-risk infants did not vary their pattern of preference across time, thus finding the audiovisual redundancy available in this part face equally salient across this period. Furthermore, group differences in the allocation of attention were observed at the end of the first year of life. At this time, groups showed opposed patterns of selective attention. Whereas low-risk infants preferred to rely on the talker’s mouth, high-risk infants preferred to look at the eyes.
Altogether, the results of this thesis suggest that high-risk infants show atypical shifts in selective attention from the second half of the first year of life and differ from their typical peers in this mechanism at the end of this period. This finding constitutes an important step forward in the study of siblings at genetic risk for ASD, since a deficit in this attentional mechanism may compromise the fidelity with which these infants process the audiovisual speech embedded in their communicative experiences, thus constituting an early expression of the linguistic difficulties usually observed in them. The implications of these results are discussed in light of domain-general theoretical approaches for the emergency of ASD, with special emphasis in the Neuroconstructivist approach.
