But was an extra photopigment all that was needed to evolve trichromatic vision? 但是是否另一种感光色素必须完全进化成三色视觉？
In this view, trichromatic color vision can be considered a hobby of the preexisting spatial vision system. 或许也没有这个必要，如果从这角度来看，我们可以把三色视觉看成既有空间视觉系统的次要活动。
A certification of colour vision shall be valid for a maximum period of six years. 色觉视力证书的最长有效期应为六年。
Our experiments provided evidence that birds use all four cones in their color vision. 我们的实验证明，鸟类的色觉使用了所有四种锥细胞。
