Tara Sethi

Date of Award


Document Type


Degree Name

Master of Science in Human Factors in Information Design

First Advisor

Dr. Mounia Ziat


In recent years, dark mode displays have become a popular user interface design trend. Major software providers have promised several benefits to using dark mode (negative polarity) displays. However, most of the prior research showed that light more (positive polarity) is more beneficial to human performance. In this work, we investigated the effect of display polarity (negative and positive) on cognitive load, subjective mental effort, subjective task difficulty, and emotion to assess whether the popularity of these displays is related to aesthetic qualities or true physiological benefits. As the dark mode trend has been observed mostly in younger populations, two age groups (younger adults and older adults) tested both displays under bright and dim environments through writing and search tasks. Eye-tracking was used to collect search time, pupil diameter, and fixation count. Results showed that there was an increase in cognitive load elicited by negative polarity displays, as reflected by an increase in search time and pupil diameter for older adults in a bright environment and younger adults in a dim environment. Mental effort scores corroborated these results, where scores were higher for older adults using negative polarity while performing the search task in a bright environment. This group also reported more positive emotions using positive polarity, while younger adults expressed more interest in negative polarity. These results suggest that older adults use positive polarity to avoid mental fatigue, while younger adults prefer using negative polarity in a dim environment for aesthetic reasons.