Since the discovery of the Ternus illusion there has been an abundance of research into how and why it occurs. As can be deemed from research above, one of the most critical factors appears to be the length of the ISI, as it seems to be a heavy determinant in which percept becomes apparent to the observer however there are many other factors implicated. A reasonable amount of the research in this area appears to be well empirically supported, such as the idea that lower level (short range processes) and higher level (long range processes) are involved in determining which illusion is perceived.