translation.en: Bats, I've even suggested, use perceived hues, such as red and blue, as labels, internal labels, for some useful aspect of echoes -- perhaps the acoustic texture of surfaces, furry or smooth and so on -- in the same way as swallows or indeed, we, use those perceived hues -- redness and blueness, etc. -- to label long and short wavelengths of light.
translation.zh: 我甚至猜测蝙蝠使用察觉到的色调，如红色和蓝色，作为标签 来对回声中一些有用的方面进行标注， 例如表面的声学质地是平滑的还是粗糙的等等， 同样的，燕子及我们人类使用 红色、蓝色等察觉出的色调 来对光线波长的长短进行标识。