As the monkey looked at the face, blood vessels supplying nerve cells in the visual part of the monkey's brain transiently swelled in exactly the same pattern.

The picture is actually a miracle in its own right: the high-speed video camera that shot it was trained on the exposed brain of a monkey staring at a yellow smiley face.

Just then, suddenly, there appeared on the window-sill a large monkey, grey, with a black face and bushy hair over the forehead.