Dark vs light stimuli in psychophysical tasks: a search for possible moderators of the contrast polarity effect M Gerdes, C Meinecke |
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Institute of Psychology, University of Erlangen-Nuremberg, Germany
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| The goal of studying contrast polarity is to determine if information for display users should be presented in dark print on a lighter background or vice versa. The existence of a contrast polarity effect, i.e. the superiority of dark stimuli compared to light ones, is controversial in the literature [e.g. Chan and Lee, 2005, Behaviour & Information Technology, 24(2), 81-91; Buchner et al, 2009, Ergonomics, 52(7), 882-886], yet the reasons for why the effect is so unstable have not been looked into. We conducted a series of psychophysical experiments involving basic, non-semantic stimuli like lines or arrows, in order to keep top-down influences at a minimum. Absolute contrast of dark vs light stimuli was equalized according to Michelson and Weber contrast measures, so that results can be compared to a variety of previous studies. Basic variables such as stimulus duration or background luminance were then systematically varied to test for their influence on the size/direction of the polarity effect. Our results confirm the general impression that the effect is rather unstable and occurs only in very specific experimental setups. This leads us to question the practical relevance of contrast polarity in applied settings. |
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