Oh, I believe humans can think alright, but they also have the ability to order their minds to disregard anything potentially nasty because it appears too difficult and scary to deal with it.

As my flight instructor once said to me,: "If you are flying one day and you see that your instruments are showing wrong indications, don't look at them again, because it is too scary. Just make sure, when you hit the ground, you make a big enough hole, so we don't have to clean up the mess."

It would appear, humanity will make a big hole.
I just hope animals will not be sucked into it as well.