Search

This study explores a proposition that individuals with dyslexia develop enhanced peripheral vision to process visual-spatial information holistically. Participants included 18 individuals diagnosed with dyslexia and 18 who were not. The experiment used a comparative visual search design consisting of two blocks of 72 trials. Each trial presented two halves of the display each comprising three kinds of shapes in three colours to be compared side-by-side. Participants performed a conjunctive search to ascertain whether the two halves were identical. In the first block, participants were provided no instruction regarding the visual-spatial processing strategy they were to employ. In the second block, participants were instructed to use a holistic processing strategy-to defocus their attention and perform the comparison by examining the whole screen at once. The results did not support the hypothesis associating dyslexia with talents for holistic visual processing. Using holistic processing strategy, both groups scored lower in accuracy and reacted faster, compared to the first block. Impaired readers consistently reacted more slowly and did not exhibit enhanced accuracy. Given the extant evidence of strengths for holistic visual processing in impaired readers, these findings are important because they suggest such strengths may be task dependent. Copyright © 2016 John Wiley & Sons, Ltd., (Copyright © 2016 John Wiley & Sons, Ltd.)

An observer's pupil dilates and constricts in response to variables such as ambient and focal luminance, cognitive effort, the emotional stimulus content, and working memory load. The pupil's memory load response is of particular interest, as it might be used for estimating observers' memory load while they are performing a complex task, without adding an interruptive and confounding memory test to the protocol. One important task in which working memory's involvement is still being debated is visual search, and indeed a previous experiment by Porter, Troscianko, and Gilchrist (Quarterly Journal of Experimental Psychology, 60, 211-229, 2007) analyzed observers' pupil sizes during search to study this issue. These authors found that pupil size increased over the course of the search, and they attributed this finding to accumulating working memory load. However, since the pupil response is slow and does not depend on memory load alone, this conclusion is rather speculative. In the present study, we estimated working memory load in visual search during the presentation of intermittent fixation screens, thought to induce a low, stable level of arousal and cognitive effort. Using standard visual search and control tasks, we showed that this paradigm reduces the influence of non-memory-related factors on pupil size. Furthermore, we found an early increase in working memory load to be associated with more efficient search, indicating a significant role of working memory in the search process.

A previous study (Vision Research 51 (2011) 1192-1205) found evidence for semantic guidance of visual attention during the inspection of real-world scenes, i.e., an influence of semantic relationships among scene objects on overt shifts of attention. In particular, the results revealed an observer bias toward gaze transitions between semantically similar objects. However, this effect is not necessarily indicative of semantic processing of individual objects but may be mediated by knowledge of the scene gist, which does not require object recognition, or by known spatial dependency among objects. To examine the mechanisms underlying semantic guidance, in the present study, participants were asked to view a series of displays with the scene gist excluded and spatial dependency varied. Our results show that spatial dependency among objects seems to be sufficient to induce semantic guidance. Scene gist, on the other hand, does not seem to affect how observers use semantic information to guide attention while viewing natural scenes. Extracting semantic information mainly based on spatial dependency may be an efficient strategy of the visual system that only adds little cognitive load to the viewing task., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Highlights: [•] Focus of peri-saccadic mislocalization follows salient stimuli, not necessarily the saccade goal. [•] Attracting effect of salient stimuli is not diminished by visible background. [•] Absence of salient stimulus including saccade target results in less compression. [•] A strong visual reference can influence perceived location of peri-saccadic flashes. [ABSTRACT FROM AUTHOR]