The effect of redundant stimulus elements on visual discrimination as a function of element heterogeneity,equal discriminability,and position uncertainty

Garner and Lee (1962) showed no gain in visual discrimination accuracy with addition of redundant stimulus elements. Eriksen and Lappin (1965) showed a substantial gain. One experiment reported here indicates that the discrepancy is not due to the fact that the earlier experiment used heterogeneous stimulus elements. A second experiment indicated that the gain in discrimination accuracy does occur when the additional stimulus elements have the same discriminability as the original elements. It also showed that position uncertainty itself has no effect on the gain with redundant elements, but is a convenient procedural device for maintaining fixation and thus equal element discriminability. Three models of perceptual independence fit the data.