Lighting and recognition of emotion conveyed by facial expressions

A recent study examined how luminance and spectral power distribution affect recognition of facial expression, a proxy for pedestrians' judgements concerning the apparent intent of other people. This paper describes a repeat study which included a greater number of test luminances, a third type of lamp, and an additional, shorter duration of observation (500 ms). Luminance and distance had significant effects on expression recognition; the effect of lamp was not significant and the effect of duration was suggested to be significant only within the escarpment region of the performance versus luminance relationship. The results were used to estimate appropriate light levels for outdoor lighting. A luminance of 1.0 cd/m2 permits facial expressions to be identified with a 50% probability of correct identification at a distance of 15 m.