See anything unusual about these two faces? They are certainly similar. The face on the left could belong to the sister of the man whose face is seen on the right. Well, look more closely. The two images are identical, but one is reproduced with lower brightness than the other. The lower the brightness, the more "male" the face looks.

This illusion is actually quite frightening, and if you are easily disturbed you probably should not try to view it. What happens: this is just an album of photos of celebrities, and they are all better looking than the average human, but if you fix your eyes on the faint + at the center of the image, as the photos are rapidly sorted through, you will see the faces distort into visages of utter monstrosity! Of course the images are not distorted in any way, they just switch rapidly from one normal face to another.

One more somewhat disturbing illusion, usually called the "Thatcher Illusion" because it was first demonstrated using a photo of former British Prime Minister Margaret Thatcher. What we see here is a version of a photo on an album cover by singer Adele, with a more normal photo included for comparison. Do you see anything strange about the black and white photo?

When we look at people's faces, we tend to look at the eyes first. If the rest of the face is turned upside down, but the eyes remain in their normal orientation, we tend not to notice. But of course when the whole image is turned right-side up, and we can compare to the inverted version, the problem with the eyes is instantly noticed!