Selective adaptation patterns of simple contours and geometrical illusions under monocular stimulation were studied with five subjects. A strict property analyzer model predicted that adaptation patterns would mirror figural contours of both types of forms. The results supported this hypothesis: the geometrical illusions generated adaptation patterns reflecting their physical stimulus properties rather than the illusory percept resulting from contextual juxtaposition. The results are discussed with respect to a model of feature extraction which assumes that property analyzers possess a sensitivity bandwidth.