As soon as a mom and her three kids arrived, two of her kids hurried to have the "Monkey face" painted on them while the mom selected the face of "Zhang Fei".

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.