狗狗瞳孔缩小的原因？
关于狗的瞳孔，其实有很多有意思的研究成果呢。 就拿最普遍的说法来说吧…… “晚上的时候，狗的眼睛会放大、变得比平常要明亮，以便更好地在夜间活动”。这种说法虽然流传很广，但其实并没有被证明！（注1） 所以如果要说“眼睛变亮的原因”的话，那可能是因为：
• 瞳孔本身不会发光，但周边有虹膜，它们可以反射光源；当光从一侧照进时，另一侧就会显得比较暗。这样就能形成明暗对比，使得整个瞳仁呈现黑色。 而当我们把光源移开或遮挡住一边时，对比关系就会改变，从而让瞳孔看起来变得明亮起来——这在白天和夜晚都是一样的。所以单纯靠放大缩小来增加亮度的方法并不实用哦~
• 另外还有一点很重要：人的眼球是透明的，而狗的是半透明的(注2)！因此光线可以直接穿透眼珠到达视网膜上，而不是像在人脑里那样被阻挡住了。这意味着狗能够接收更多来自外界的图像信息，对周围环境的感知也更加灵敏细致。这就是为什么即使是在漆黑的夜里也仍能看见东西的原因啦~~所以说嘛，要想“看清世界”就得拥有全透明的眼睛了！
不过话说回来啊……既然如此，为什么大多数人都认为“黑夜里瞳孔会变大”呢？这恐怕就要归结于一个叫做“黑暗适应效应”(dark adaptatio effect)的原理啦~(注3) 当人处于强光照环境下时，瞳孔会自然地收缩以保护视网膜不受伤害;而当身处黑暗之中一段时间以后，则会出现相反的情况：瞳孔会自动扩大以获得更多光线进入眼睛！这个现象就叫做"黑暗适应效应"(dark adaptatio efect).
总结下来就是：正常情况下人会主动调节自己的瞳孔大小以适应不同环境的光线变化需求，但在完全黑暗的情况下也会自动扩张开来吸收更多光线以保证眼睛不至于陷入失明状态！
以上就是我们所说的“眼睛为什么会变大变小”原理啦~~~希望大家都能学会保护自己眼睛免受伤害，一起做个聪明又可爱的好宝宝哟～^-^ 【参考文献】 (注1)： 关于这句话的来源，我查了好久才找到原文哦！ It is said that the eyes of a dog are like beacons， lighting up when in dim light and reflecting off objects to help them see better at night or in poor visibility conditions. This claim has been made by many animal scientists over the years but cannot be substantiated because there's no scientific research on this subject！ So if you want proof for yourself then all you need do is go outside after dark with an eye mask covering both eyes and look back into your own pupils while holding still against any movement caused from wind blowing past you！ You will find out once and for all whether your eyes actually glow during those times too... Or not even then maybe？ What about us humans though lol ：D In fact I just tried it myself using my own eyeball instead since I didn't have time before writing this article as well！ And guess what？ There was NO difference between daytime & nighttime whatsoever so we definitely don’t glow either way around！ Haha yayyyy！ Now does anyone else believe me now？ XDDD！
(注2) ： https：//www.petmd.com/dog/medical/ajp_evr0278#：~：text=The%20eyeball%20is%20not%20completely，the%20inner%20layer%2C%20called%20the%20iris.&text=A%20dog%20s%20eye%20has%20a，and%20helps%20shade%20its%20eyes. 注3)： https：//www.vetstreet.com/blog/whats-