“What you are seeing at the present moment is not a fresh snapshot of the world but rather an average of what you’ve seen in the past 10 to 15 seconds,” said study author Jason Fischer, a neuroscientist at the Massachusetts Institute of Technology.

He showed subjects an image of a black-and-white grating tilted at a random angle for half a second, then asked them to identify the orientation of the grating they just saw. Then a few seconds later, another grating popped up, and they were to identify its angle.

If the subjects saw the gratings completely accurately, their answers would have no dependence on past gratings, since the orientations were random. Instead, their answers showed a strong influence from the angles they saw previously, even up to 15 seconds earlier.