Humans can, too, though not very well. Stare at a bright white LCD—you should see orthogonal double-fan shapes, one bluish, one yellowish.

I personally see it more readily from red LED digits on my alarm clock at night. IDK if it's generally better conditions or biological difference.

LEDs don't produce polarized light. You might be seeing the matrix scanning.

Don't know why I said LED. Alarm clocks are almost never LED. It's a backlit LCD.

They can see 6 different types of polarization though.