Proximal vergence is sometimes also called voluntary vergence, which however more generally means vergence under voluntary control and is sometimes considered a fifth type of vergence.[4] Voluntary vergence is also required for viewing autostereograms as well as for voluntary crossing of the eyes. Voluntary convergence is normally accompanied by accommodation and miosis (constriction of the pupil); often however, with extended practice, individuals can learn to dissociate accommodation and vergence.[5]