Amodal completion and localization

In a three-line vernier acuity task, a central line was localized between two aligned line segments. Accuracy did not improve when the segments formed a unified amodally completed percept. In a two-line vernier acuity task, a line was localized below a target line placed next to a physically segmented flank stimulus. Shifts in mean points of subjective equality suggested that amodally completed segments influenced localization. Previous conflicting findings are explained by a representation that is available early to influence perceived alignment. However, position tuning is poor. This representation may be realized physiologically by interpolation responses between amodally completed segments.