Patrick kelly¹, Jefferson Ortega¹, David Whitney¹; ¹University of California Berkeley

Many studies have found serial dependence in perceptual judgments of all kinds of features, objects, and abstract impressions. Fewer studies have investigated serial dependence for compound features and it remains less clear whether serial dependence can occur independently for different dimensions within a given stimulus. Here, we investigated this with combinatorial stimuli consisting of a skin lesion with a superimposed orientation texture. The two dimensions of the compound stimulus were orthogonal and randomly distributed. These stimuli were chosen because they are not configural objects like faces, are unfamiliar, can be approximately equated in terms of discriminability, and are translationally relevant to clinical settings. We first approximately equated discriminability of the two features. We then measured serial dependence in both domains using a 2 alternative forced choice task consisting of two separate feature judgments across two blocks of trials in which participants viewed the same set of stimuli. We found an overall significant level of serial dependence in both orientation (p < 0.001, permutation test) and malignancy (p = 0.036, permutation test) feature domains. However, there was not a clear relationship between the magnitude of serial dependence in the orientation dimension and that in the malignancy dimension at the level of individual observers (r = 0.113, p = 0.616). The results suggest that serial dependence can occur in different dimensions within the same object and that these effects may be independent of each other.