Have you noticed how on Mac OS menus, when you click an item, the selection blinks a couple times? You probably haven't, because it's very subtle. We probably perceive it unconsciously.
But this pattern serves a purpose: it directly highlights the item we clicked. For that split second, you get a visual confirmation that your click registered, and that an action was triggered.
I'm surprised this pattern is not predominant on the web. Google's Material design gets us half-way there, with the implementation of a radial action. This is a visual ripple of ink spreading outward from the point of input.
For fun, I re-created the blink animation on a plain dropdown, and I plan on using this in future projects and menus.