Importance of global information in vernier acuity

Noisy vernier configurations were generated by normally distributing the lateral displacements of dot elements forming vertical dotted lines. Observations with noisy configurations were compared with thresholds obtained with noise-free lines. In configurations with gap, we have found, through independent perturbation of the end regions adjacent to the gap, that the entire length of the line was actively processed. In an experiment with noisy abutting lines, the threshold as a function of line length exhibited only a slight upward shift relative to the curve obtained with noise-free configurations. Since it is not possible to interpret all the results through a comparison of local positional information extracted from the stimulus configuration, we conclude that global information is also involved in the processing.