title: Averaging, not internal noise, limits the development of coherent motion processing.
abstract: The development of motion processing is a critical part of visual development, allowing children to interact with moving objects and navigate within a dynamic environment. However, global motion processing, which requires pooling motion information across space, develops late, reaching adult-like levels only by mid-to-late childhood. The reasons underlying this protracted development are not yet fully understood. In this study, we sought to determine whether the development of motion coherence sensitivity is limited by internal noise (i.e., imprecision in estimating the directions of individual elements) and/or global pooling across local estimates. To this end, we presented equivalent noise direction discrimination tasks and motion coherence tasks at both slow (1.5°/s) and fast (6°/s) speeds to children aged 5, 7, 9 and 11 years, and adults. We show that, as children get older, their levels of internal noise reduce, and they are able to average across more local motion estimates. Regression analyses indicated, however, that age-related improvements in coherent motion perception are driven solely by improvements in averaging and not by reductions in internal noise. Our results suggest that the development of coherent motion sensitivity is primarily limited by developmental changes within brain regions involved in integrating motion signals (e.g., MT/V5).
authors.affiliation: Centre for Research in Autism and Education (CRAE), Institute of Education, University of London, 55-59 Gordon Square, Institute of Education, London WC1H 0NU, UK. Electronic address: c.manning@ioe.ac.uk.
authors.forename: Catherine
authors.initials: C
authors.lastname: Manning
authors.affiliation: UCL Institute of Ophthalmology, University College London, Bath Street, London EC 1V9, UK; NIHR Biomedical Research Centre at Moorfields Eye Hospital, 162 City Road, London EC 1V 2PD, UK.
authors.forename: Steven C
authors.initials: SC
authors.lastname: Dakin
authors.affiliation: UCL Institute of Ophthalmology, University College London, Bath Street, London EC 1V9, UK.
authors.forename: Marc S
authors.initials: MS
authors.lastname: Tibber
authors.affiliation: Centre for Research in Autism and Education (CRAE), Institute of Education, University of London, 55-59 Gordon Square, Institute of Education, London WC1H 0NU, UK.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Pellicano
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D010775:Photic Stimulation; D013997:Time Factors
keywords: Direction discrimination; Motion processing; Visual development