subsequent contrast effect if one stares at the cross on the left side for about a minute and then shifts his glance on the cross at the right side, one will notice that the areas on grey background will appear slightly coloured, each in the corresponding
x![From the series "Edifying Thoughts of a Tobacco Smoker"](https://www.premioceleste.it/indi/_pics/0/5/2017-101128-422053_20504_6969_t.jpg?m=1498648926 "From the series "Edifying Thoughts of a Tobacco Smoker"")
