Look closely now the two figures are shown on the right. Could you tell us which of the two central orange circles is larger, the one on the right or the one on the left?
If you have answered that the older one is the one on the left, you have failed. The two circles are exactly the same, what makes us make a false interpretation are the surrounding circles, since we compare the red inner circle with its more adjacent ones, so that we see them large or small in relation to the latter.
You can find more information about this optical illusion on Wikipedia.