Extensional models represent each stimulus only once, meaning conflicting perceptual data about the same moment t yields contradictory experiences (the spot being perceived as both stationary and in motion simultaneously).

Coming from a very different direction, Grush has argued (2005b, 2006, 2007, 2016) that Retentional models have a distinct advantage over Extensional models when it comes to accommodating certain ‘temporal illusions’. The relevant category of cases are those where a stimuli occurring later than a time t affects the character of what is perceived as occurring at t itself; the so-called flash-lag effect and the phi-phenomenon fall into this category. These instances of (apparent) retro-active caus