Visual illusions proper should be distinguished from some related phenomena.

They are a related phenomenon to the dead dog parties common at the end of science fiction conventions.

A related and more general phenomenon is that of subjective validation.

The answer may be that since 1981, when most of the fraud has occurred, we have witnessed two related ideological phenomena.

A related phenomenon is exceptional isomorphism, when two series are in general different, but agree for some small values.

Nationalism, a related though distinct phenomenon, has perhaps fared even worse.

Bubble talk now tends to deal with two related but separate phenomena.

Probably the seasonality and the number of species are related phenomena.

In psychology, a related phenomenon to the false dilemma is black-and-white thinking.

Mainly dedicated to the apparent motions of the Sun and to related phenomena.