The polarity effect refers to a better performance in visual tasks when stimuli are presented dark on a light background (positive polarity) as compared with light on dark (negative polarity). Most studies examined polarity using conventional monitors for stimulus presentation. Only recently, research has been extended to virtual reality (VR). VR studies usually differ methodologically from traditional research, e.g. by using larger stimuli due to limited display resolutions, and focus on stimulus identifiability. Reaction times, which are crucial for VR applications that involve quick reactions to visual information, are understudied.
We therefore used a high-resolution VR headset to experimentally test the polarity effect in VR with tasks and stimuli similar to traditional research, measuring both identifiability and reaction times. Based on previous research, we expected faster and more accurate reactions with positive polarity. In a one-factorial within-subject design, 27 participants reacted to 96 increasingly smaller Landolt-C optotypes via key-presses, and verbally indicated spelling and grammar errors in 18 texts. Half of the stimuli were presented in positive and half in negative polarity. Afterwards, experienced difficulties were surveyed.
As assumed, in positive polarity, correct reactions to optotypes were faster, and significantly more words were read and more errors identified. No significant effect in optotype identifiability occurred. Participants reported more blur in negative, yet more glare in positive polarity presentation, overall preferring negative polarity. The results suggest superiority of positive polarity in VR, especially when tasks require fast reactions, and a need for further research on discrepancies between subjective preferences and performance.