Abteilung Allgemeine Psychologie, Giessen University, 35394 Giessen, Germany.
Curr Biol. 2017 Jun 19;27(12):R586-R588. doi: 10.1016/j.cub.2017.05.008.
From intense sunlight in bright snow down to a moonless night in a dark forest, we can use light to recognize objects and guide our actions. This remarkable range mainly rests on having two different types of photoreceptors, the rods and the cones. The cones are active under daylight conditions, allowing high acuity and color vision. Rods are mainly active under very dim illumination conditions and have an exquisite sensitivity to light [1]. There are obvious detriments to visual perception in near darkness, such as a central scotoma, reduced motion perception [2], and most of all a lack of color [3]. There is only one type of rod, and thus intensity and wavelength differences cannot be disentangled when only the rods are active. This is captured well by the old saying "at night all cats are gray", meaning that different colors inevitably get mapped onto different shades of gray. Here we show that the perception of lightness is also different for night vision: our results indicate that surfaces that appear to be white under daylight conditions, at best, appear medium gray under night vision, suggesting that activation of the cones is necessary for the perception of white.
从强烈的阳光到白雪皑皑的明亮雪地，再到没有月光的黑暗森林，我们可以利用光线来识别物体并指导我们的行动。这种显著的范围主要依赖于两种不同类型的光感受器，即视杆细胞和视锥细胞。视锥细胞在日光条件下活跃，可实现高清晰度和色觉。视杆细胞主要在非常昏暗的光照条件下活跃，对光具有极高的灵敏度[1]。在几乎黑暗的环境中，视觉感知会有明显的损害，例如中央暗点、运动感知降低[2]，最重要的是缺乏颜色[3]。只有一种类型的视杆细胞，因此当只有视杆细胞活跃时，强度和波长的差异无法区分。这很好地解释了一句古老的谚语“在黑暗中所有猫都是灰色的”，意思是不同的颜色不可避免地会映射到不同的灰度上。在这里，我们表明对光亮度的感知在夜视中也不同：我们的结果表明，在白天看起来是白色的表面，在夜视条件下，最多呈现中等灰色，这表明视锥细胞的激活对于白色的感知是必要的。
