Abstract
The phenomenology of the Thatcher illusion is often used as a demonstration of configural processing. Thatcherised faces are created by inverting the eyes and mouth within the context of the face. When faces are upright, this produces a grotesque appearance. However, when faces are inverted, perceived grotesqueness disappears. The Thatcher illusion is traditionally thought to arise because participants compute configural relations when faces are upright, but rely on featural processing when faces are inverted. This study investigated whether evidence of configural processing of Thatcher faces could be found using constructs defined by general recognition theory (Ashby & Townsend, 1986). Churches were used as control stimuli. Participants were presented with upright and inverted faces and churches that had the eyes (windows) inverted, the mouth (door) inverted or both the eyes (windows) and the mouth (door) inverted, and observers responded with judgments about both features. The results showed violations of informational independence, informational separability and decisional separability suggesting that the Thatcher illusion is underpinned by a strong form of configural processing.