On the scaling of visual space from motion--in response to Pizlo and Salach-Golyska.

Pizlo and Salach-Golyska (1994) have raised an important question about the validity of the interpretation of experiments reported by Lappin and Love (1992)--based on the fact that alternative cues in the image plane might have supported the shape discriminations in those experiments. The meaning of the hypothesis that visual space may be scaled by congruence under motion is clarified, pertinent evidence is reviewed, and new experimental evidence is reported. We conclude that visual space can be metrically scaled by congruence of moving shapes.