Averaging, not internal noise, limits the development of coherent motion processing.
Bottom Line: 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.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).
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: email@example.com.Show MeSH
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Mentions: Levels of internal noise reduced with age, with 5-year-olds having mean levels of 9.62° and 9.69° in the slow and fast conditions, respectively, which reduced to 6.72° and 4.80° in the adult group. To characterise the rate of developmental changes in estimated internal noise, log internal noise values were plotted as a function of log age and fit with a straight line (Fig. 3A). We then compared the developmental trajectories for slow and fast speeds using the ANCOVA method outlined by Thomas et al. (2009). In this method, within-subjects effects are initially examined using an ANOVA before assessing age-related changes by adding a covariate (as within-subjects effects are masked when a between-subjects covariate is added; Delaney and Maxwell, 1981; Thomas et al., 2009). An initial ANOVA with speed condition (slow, fast) as a within-subjects factor revealed that significantly higher levels of log internal noise were found in the slow (M = .87, SD = .24) than the fast condition (M = .79, SD = .25), F(1,122) = 12.24, p < .01, . Next, an ANCOVA was conducted by adding log age into the model as a covariate. Overall, log internal noise reduced significantly with age, F(1,121) = 13.42, p < .01, . Also, there was a significant interaction between log age and speed condition, F(1,121) = 4.76, p = .03, , indicating a significantly steeper rate of development in the fast condition than the slow condition.
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: firstname.lastname@example.org.