“…Perceptual learning occurs for different kinds of tasks at different levels of visual analysis (figure 1). It improves detection or discrimination for single features such as orientation (Dosher & Lu 1998, Dosher & Lu 1999, Schoups et al 1995, Vogels & Orban 1985), spatial frequency (Bennett & Westheimer 1991, Fiorentini & Berardi 1981), phase (Dosher et al 2010, Fiorentini & Berardi 1980), contrast (Adini et al 2004, Dorais & Sagi 1997, Sowden et al 2002), color (Casey & Sowden 2012, Özgen & Davies 2002, Thurston & Dobkins 2007), acuity (Bennett & Westheimer 1991, Westheimer 2001), and hyper-acuity (Crist et al 1997, McKee & Westheimer 1978, Poggio et al 1992). It improves pattern discrimination in tasks involving compound stimuli (Fiorentini & Berardi 1980, Fiorentini & Berardi 1981), textures (Ahissar & Hochstein 1993, Karni & Sagi 1991), depth (Fendick & Westheimer 1983, Ramachandran & Braddick 1973), and motion (Ball & Sekuler 1982, Lu et al 2006, Lu et al 2005, Matthews & Welch 1997, Watanabe et al 2002).…”