Visual Stress and Cognition: An investigation of the impacts of visual stress on lexical decision making Joshua Gietzen, Yu-Chi Tai, PhD, John R. Hayes, PhD, James E. Sheedy, OD, PhD Vision Ergonomics Research Lab Pacific University College of Optometry 4 June 2009

Background Visual Stress produces specific physical symptoms (Sheedy et al., 2003) Certain stressors yield predictable symptoms Cognitive tasks under visual stress are performed with equal accuracy to controls (Garzia et al., 1989) Yet completion time is longer

Study Design Measured “comprehension” in terms of response time to lexical decision task Decide if a word is a noun or not 360 trials - 50% nouns & 50% non-nouns Manipulated viewing conditions Control ( 12-point font) Small font ( 5-point) Glare (white screen) Blurry images (smashed images by adding a cross-hatch background, see image to right) * Not to scale

How to measure cognitive processing time? Priming Scheme Manipulated prime types Visual vs. Semantic vs. Neutral Target word: CLASS Semantic - CATEGORY Visual - GLASS Neutral - BOOKS 100 ms glass 50 ms XXXXX Lexical Decision through voice key (times out: 1500ms) class

Results – RT for correct trials

Results – RT for incorrect trials

Results – Overall Accuracy

Conclusions Small Font condition degrades the visual presentation. Increases use of cognitive resources to integrate visual information, leading to an increase in comprehension time. Small Font condition is more difficult to process, leads to a decrease in correctness of responses. Small Font can create more cognitively stressful conditions.

Acknowledgement This study was supported by Microsoft Corporation.