Smaller pupil size and better proofreading performance with positive than with negative polarity displays

Abstract

The ‘positive polarity advantage’ describes the fact that reading performance is better for dark text on light background (positive polarity) than for light text on dark background (negative polarity). We investigated the underlying mechanism by assessing pupil size and proofreading performance when reading positive and negative polarity texts. In particular, we tested the display luminance hypothesis which postulates that the typically greater brightness of positive compared to negative polarity displays leads to smaller pupil sizes and, hence, a sharper retinal image and better perception of detail. Indeed, pupil sizes were smaller and proofreading performance was better with positive than with negative polarity displays. The results are compatible with the hypothesis that the positive polarity advantage is an effect of display luminance. Limitations of the study are being discussed.

Abstract

Practitioner Summary: Digital displays are ubiquitous. Understanding of the mechanisms underlying the perception of text is important for good display design. The hypothesis that bright positive polarity displays lead to small pupils and a sharp retinal image that improves reading cannot be rejected and is thus maintained. Positive polarity displays are recommended.

Keywords::

• display polarity
• pupil size
• eye tracking
• display design
• screen luminance

Acknowledgements

We thank Anne-Kristin Elsner von Gronow and Christian Hoverath for their assistance with data collection. We also thank Frederik Aust for his support with data analysis.

Notes

^1. Different explanations for the function of the pupillary light reflex have been discussed, such as optimising visual resolution under differing lighting conditions, increasing sensitivity through the change in area of the pupil during dark adaptation, maintaining a constant retinal illumination, protecting the retina from dangerously bright lights and preparing the eye in bright light for a subsequent return to the dark (Laughlin 1992; Woodhouse 1975; Woodhouse and Campbell 1975).