ABSTRACT
This chapter describes a distance aftereffect model in which slow fusional vergence is accompanied by tonic innervation, the resulting phoria represents a lag in the vergence posture from its previous position and results in a distortion in distance perception. It discusses induction and adaptation experimental paradigms. The chapter represents an exploration of the effects on distance perception of factors that condition hysteresis effects in the vergence control system. Phoria represents the degree to which the ocular axes verge in front of, at, or beyond a given target in the absence of fusional stimuli. Two methods were used to investigate hysteresis effects in the form of an induced phoria and to examine their effects on distance perception. They are adaptation paradigm and induction paradigm. An examination of the relation between hysteresis effects in the vergence system and distance aftereffects is provided by a comparison of binocular and monocular exposure conditions in the adaptation paradigm.
