Is it something to do with the idiom of putting a thumb on the scale, meaning using your power to influence the outcome of something?
he's stepping on the scale making the guy seem heavier than he is
Furthermore the man on the scale is faced the other way and wouldn’t know someone is stepping on the scale. There’s an element of theory of mind there. You would have to understand that the man on the scale is unaware of Obama’s action.
The article points this out and several things we all instantly recognize.
Thanks. I was looking at the picture on my phone and it was difficult to see what was going on in the picture.
Luckily the article explains it right below the caption ;-)
But you understand why people might find it funny, and what people in the image are thinking, you have a mental model of them. That's the point.
That’s because it’s very posed so it’s not that funny.