Step 1

First you need an image of a well known person, I chose Phoney Blair, the once Prime Minister of Great Britain

The Eyes

Using a lasoo tool, sometimes called a cloning tool, select an area around the eyes. Note how I have selected a small figure of 8. Make the selection hard edged and not feathered or tapered.

We will be using a blur tool later but as the image has many skin tones it is best not to taper the cloned eyes

Step 2

Offsetting the eyes

Drag the selection from Step 1 down, this can be done by trial and error but I found that half the height of the eyeball was about right

Step 3

Now the mouth

Just like I did in Step 1, select the mouth using your lasoo/clone tool. I roughly made a border of 1 mouth height around it.

Step 4

Drag the mouth

As in Step 3, drag the mouth downwardsso that the edge of the selection touches the bottom of the lower lip

Save your work

The finished product

I have had reports that you can either see this or you cannot. I do not know the reason why some people cannot but this illusion is generally caused when our brains visualise a face with 2 eyes and a mouth and "sees" the ratio and relationship to the distances but when alternative feature appear it gets confused and there is confusion in our perception.

I have found by trial and error that this illusion only really works well when the person's face has blue or green eyes and they are quite prominent, as is Tony Blair's

This is a fun little animation I did, using the method above but animating each step. Again, you can see the example (Hugh Grant) has quite striking eyes and this assists in the illusion.

When I showed this to a colleague originally, they felt quite queasy:-)

Enjoy