Surprisingly, in studies to date, upright and inverted face aftereffects have been remarkably similar. All manipulations known to produce aftereffects for upright faces have, where tested, also been shown to produce aftereffects for inverted faces; these include global expansion–contraction (Rhodes et al.,
2004), vertical/horizontal expansion–contraction (Watson & Clifford,
2003; Webster & MacLin,
1999; Zhao & Chubb,
2001), gender (Rhodes et al.,
2004; Watson & Clifford,
2006), eye height (Robbins et al.,
2007), and individual identity (Leopold et al.,
2001; Rhodes, Evangelista, & Jeffery,
2009). Further, the size of inverted aftereffects is substantial, often as large as that of upright (Robbins et al.,
2007; Watson & Clifford,
2003; Webster & MacLin,
1999), and at times even larger (Rhodes et al.,
2004; Watson & Clifford,
2006; although see Rhodes et al.,
2009). The only result that might be considered, at first glance, to be evidence of a qualitative difference between upright and inverted face aftereffects is the finding that the aftereffects derive from partially separable sets of neurons (i.e., transfer of aftereffects between upright and inverted is less than 100%, and it is possible to induce simultaneous opposite aftereffects to upright and inverted faces; Guo, Oruc, & Barton,
2009; Robbins et al.,
2007; Watson & Clifford,
2003,
2006; Webster & MacLin,
1999; Rhodes et al.,
2004). However, this result does not demonstrate a qualitative difference because even upright faces are not all coded by one common set of neurons (e.g., see the “Jennifer Aniston neuron,” Quiroga, Reddy, Kreiman, Koch, & Fried,
2005; and simultaneous opposite aftereffects for gender, race, and individual identity in upright faces, Jaquet, Rhodes, & Hayward,
2007; Little, DeBruine, & Jones,
2005; Robbins & Heck,
2009; Yamashita, Hardy, DeValois, & Webster,
2005).