If simulations are being compared to reaction time data from a perceptual experiment (e.g. lexical decision), then typically an activation threshold is used.
A more plausible theory to explain motion perception (at least on a descriptive level) are two distinct perceptual illusions: phi phenomenon and beta movement.
According to the fluency account, this is because infants share perceptual equipment that make them process consonance in music more easily than dissonance.
Moreover, these experiences exhibit an intense, active perceptual involvement that he calls aesthetic engagement, which belies the traditional claim of aesthetic disinterestedness.