Evidence for the role of attentive fields in masking.

A masking task was employed to determine whether predictions derived from the attentive-field postulate of assimilation theory could be verified. The distance between masking and test lines was varied both towards and away from the center of the attentive field. As predicted, masking was greater when the mask was near the center of attention than when it was located at the periphery of the field. A variation of the mathematical formula developed previously to predict visual illusions was employed to fit the individual and group functions found in this study.