It's commonly used as a brain teaser to test pupils' logic skills at school, and children seem to be able to solve it in an instant.
But despite it being a breeze for youngsters, a puzzle which asks you to identify which direction a bus is travelling in often leaves adults scratching their heads.
National Geographic has created a version of the popular puzzle showing a yellow bus with identical windows at either end - giving no clue as to which is the front or back of the bus.
The correct answer is that - if you're in the UK - the bus is travelling to the right. And the key to solving the puzzle is the fact that you can't see the passenger doors.
This means they must be on the other side of the bus, and if you're in the UK where people drive on the left side of the road this means the bus is going right. The opposite applies in the US and other countries where people drive on the right - and the bus would be travelling on the left.
National Geographic featured the popular puzzle as part of their Brain Games TV series, and said that 80 per cent of children under 10 they tested got it right instantly.
Although the teaser is not new, it's recently cropped up again as people share it on social media.
There's no specific figures on how adults have fared, but they're said to find the puzzle a lot more difficult to answer than children.
It's thought that this is down to youngsters being better at using visual cues and past experience to interpret a picture or situation.
Research from University College London and Birkbeck, University of London has found that children under 12 perceive visual information differently from adults.
They tend to use the first visual cue their brain processes to form judgments, making them less accurate but much faster.
Adults, on the other hand, use different kinds of visual information in addition to sensory cues to form judgments.