Cognitive Load and Website Usability: Effects of Contrast and Task Difficulty

Abstract

The contrast of a website doesn’t just affect its usability for low-vision individuals; it affects everyone. This study aims to evaluate the effects of contrast (low, medium, or high) on web browsing experience in normally-sighted individuals. Cognitive load associated with the task was assessed using the NASA task load index (NASA-TLX) and the usability of the website was assessed by the systems usability scale (SUS). We found that NASA-TLX scores significantly increased with the amount of time a task took, indicating an effect of task difficulty. The impact of contrast was reported during end-of-study interviews, but no significant difference was found between the three chosen contrast levels in NASA-TLX or SUS scores. This study is part 1 of a multi-part research project and future research will compare low-vision individuals to their typically-sighted peers. Together, the studies in this project aim to quantitatively determine the effects of contrast users’ web browsing experience to further accessibility research and web development guidelines.