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New Scientist TV:

Friday Illusion: Deceptive motion in Super Mario land

Caitlin Stier, video intern

In this video game clip, it looks like Mario is jumping vertically while an enemy tortoise slides by underneath him. But keep watching when the background stops moving and you'll see that their movement is not quite what it seems.

The animation, developed by cognitive psychologist Sebastiaan Mathôt from VU University in Amsterdam, is a variation of a common illusion where our perception of an object's motion is affected by a moving background. In a previous Friday Illusion post, we shared a video that exploits the same brain trick. Can you identify it?

Let us know your choice by posting the headline in the Comments section below and the first correct answer will receive a New Scientist goodie bag. Good luck!

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Stop a spinning object with your mind


I'm going with: Rotating rings create phantom spiral


Stop a spinning object with your mind :-)


I don't see that as an illusion at all -- it's just relative motion. Relative to the background they're moving up/down or left/right. When the background stops moving their motion become relative to the entire computer screen, not just the area inside the videoplayer. For it to be a true illusion there would have to be something apparently happening that is not actually happening. They are actually moving in circles depending on your frame of reference.


Both Super Mario and the tortoise are individually moving in counter clockwise circular motion in the foreground (as we see when the background stands still). They are however not synchronized in timing but opposed to each other. It is not the background that is moving. The camera is moving clockwise.


mario and the shell move in the same motion on the computer screen, in opposing circles. Moving the background in a clockwise circle makes it appear that the camera is the source of the circular motion, as mario and the shell appear to move in a linear direction relative to the background


All three: Mario, the tortoise and the background(with the camera synchronized on it) move in the same direction, counterclockwise, in circles of the same radius. Mario and the tortoise are out of phase by 180° while the background and camera are moving in between them, out by 90° from each, so this motion cancels the vertical component on the tortoises circle and the horizontal component of Mario.


yep, what I said, only the camera I guess is not moving at all now that I look at it :P


Coriolis effect


Media spin


The straight-no-chaser effect?


it took me a while to get this illusion, I thought I was suppose to see mario jumping on the tutle when the background stopped


An excellent example of the Duncker Illusion.


The background and foreground are rotating concentrically. When the background stops moving, you notice Mario and the shell moving in a concentric way.


This is the same effect as the 'Stop a spinning object with your mind' illusion

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