It is natural to expect that efficient representations would be maximally informative with respect to the actual inputs in the world. In particular, stimuli that are more likely to occur should be encoded more compactly. The primate visual system has long been known to utilize such perceptual regularities (DiCarlo & Cox,
2007; Wagemans, Elder et al.,
2012; Wagemans, Feldman et al.,
2012). For example, in natural scenes, elements tend to be cocircular, and the visual system appears to be sensitive to such regularity (Geisler, Perry, Super, & Gallogly,
2001; Sigman, Cecchi, Gilbert, & Magnasco,
2001). Another higher-level strategy, known as norm-based encoding (Leopold, O'Toole, Vetter, & Blanz,
2001; Op de Beeck, Wagemans, & Vogels,
2003; Rhodes & Jeffery,
2006), utilizes one particular regularity of the distribution of encountered exemplars from a given category, namely the center of this distribution. For example, Leopold and colleagues (
2001) demonstrated that adaptation to faces results in a perceptual shift toward the center (“norm”) in the face space and that single face-selective neurons in the macaque monkey are tuned to the average (Leopold, Bondar, & Giese,
2006), arguing that such strategy minimizes resources the system needs to learn and store stimuli.