Figure 1.

Classic illusions demonstrating holistic face coding and its specificity to the upright orientation. (A) Thatcher illusion. Flipping the eyes and mouth in the face makes the face appear bizarre in the upright orientation, but does not produce bizarreness in the inverted orientation, and indeed is usually not noticed at all when the inverted version is seen first. (B) Composite illusion. In the upright orientation, aligning the top-half of one individual with the bottom-half of another creates the illusion of a new person. This makes each half look less like the target individual than when the whole face structure is broken by misaligning the two halves (making the illusion disappear); for example, the top-half of Barack Obama looks less like Barack Obama than does the identical top-half image in the misaligned version. Note the illusion alters perception of both halves: that is, both Barack Obama (top-half) and Will Smith (bottom-half) seem to change in appearance in the aligned composite and become difficult to identify compared to the misaligned (no illusion) condition. In the inverted orientation, the composite illusion disappears, and the identity of a given half becomes equally easy to perceive in the aligned and misaligned versions. (C) Part-whole illusion. The only difference between the two images in a given orientation is the mouth. In the upright version, altering the mouth creates illusions of alteration in regions of the rest of the face (e.g., makes the nose appear shorter on left and longer on right, makes the eyes appear more interested on left and less interested on right). In the inverted version, the difference in the mouth shape can be easily seen but the illusory changes in the rest of the face are not apparent.