Visual noise effect on reading in three developmental disorders: ASD, ADHD, and DD.

Background and aims: Developmental disorders such as Autism Spectrum Disorder (ASD), Attention Deficit Hyperactivity Disorder (ADHD), and Developmental Dyslexia (DD) are reported to have more visual problems, oral language difficulties, and diminished reading skills in addition to their different diagnostic features. Moreover, these conditions also have increased internal noise and probably an impaired ability of external noise filtering. The aim of the present study was to compare the reading performance of these groups in the presence of external visual noise which disrupts the automatic reading processes through the degradation of letters. Methods: Sixty-four children and adolescents in four groups, ASD, ADHD, DD, and TD, participated in the study. Two types of stimuli were used - unrelated words and pseudowords. The noise was generated by exchanging a fixed number of pixels between the black symbols and the white background distorting the letters. The task of the participants was to read aloud the words or pseudowords. The reading time for a single letter string, word or pseudoword, was calculated, and the proportion of errors was assessed in order to describe the reading performance. Results: The results obtained showed that the reading of unrelated words and pseudowords differs in the separate groups of participants and is affected differently by the added visual noise. In the no-noise condition, the group with TD had the shortest time for reading words and short pseudowords, followed by the group with ASD, while their reading of long pseudowords was slightly slower than that of the ASD group. The noise increase evoked variations in the reading of groups with ASD and ADHD, which differed from the no-noise condition and the control group with TD. The lowest proportion of errors was observed in readers with TD. The reading performance of the DD group was the worst at all noise levels, with the most prolonged reading time and the highest proportion of errors. At the highest noise level, the participants from all groups read the words and pseudowords with similar reading speed and accuracy. Conclusions: In reading words and pseudowords, the ASD, ADHD, and DD groups show difficulties specific for each disorder revealed in a prolonged reading time and a higher proportion of errors. The dissimilarity in reading abilities of the groups with different development is most evident when the accuracy and reading speed are linked together. Implications: The use of noise that degrades the letter structure in the present study allowed us to separate the groups with ASD, ADHD, and DD and disclose specifics in the reading process of each disorder. Error type analysis may provide a basis to improve the educational strategies by appropriately structuring the learning process of children with TD, ASD, ADHD, and DD.

Contextual modulation induced by contrast and speed on direction perception.

We examined the direction perception in centre-surround multielement configurations with varying contrast and velocity to better understand the consequences of surround interactions of orientation and motion direction perception. The stimuli consisted of Gabor elements moving either parallel or orthogonal to their orientation with two different speeds. The surround motion direction varied from 0° to 315° with a step of 45°. The relative contrast in the centre and periphery was varied. The subject's task was to discriminate whether the central motion was to the left or to the right from the vertical downward. The results suggest complex interactions between the speed, contrast, and the texture elements' orientation on both sensitivity and precision of motion direction estimation in the centre and different effects of the experimental factors on the bias and discriminability of motion direction. The potential contribution of different normalization circuits on motion direction estimation is discussed. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Global orientation estimation in noisy conditions.

The present paper studies the perceived orientation of line patterns with variable elongation, line length, orientation jitter, and presentation time. It evaluates whether the internal noise and sampling efficiency evaluated by equivalent noise paradigm (Pelli 1981) depend on the spatial configuration and temporal characteristics of the stimulation. The evaluated internal noise was compared to the results of double-pass noise estimation. In addition, the eye movements of the participants during active exploration of the line patterns were recorded and analyzed with respect to the stimulus characteristics. The results indicate the presence of late internal noise and show that the internal noise and sampling efficiency strongly depend on the elongation, duration and line length of the patterns. The response time increases with the orientation jitter and with the variability in line length of the patterns. It is longer also near the reference orientation for the low levels of added external noise. These results contradict some of the major assumptions of the variance-summation model and question its applicability in characterizing the perceived orientation of multi-element patterns.

Age-related changes in sensitivity to global speed.

We examined the effect of speed magnitude and range on the sensitivity to global speed in two different age groups. Stimuli consisted of band-pass dots whose speeds were perturbed by time-correlated or -uncorrelated random noise. The observer discriminated which of two sequentially presented stimuli moved faster. We found that the Weber fractions significantly diminished with increasing the speed of standard. The older observers had higher discrimination thresholds in all experimental conditions. The noise level did not significantly affect sensitivity to global speed differences, except for older observers' performance at the highest noise level. The temporal noise correlation differently impaired the performance of the younger and the older observers. The results are discussed in relation to speed-coding mechanisms and age-related changes in motion perception.