A peripheral target displayed with close flankers appears scrambled and is more difficult to identify than when it is displayed on its own. This phenomenon, known as visual crowding, has been extensively studied in the last two decades. Crowding is thought to be a major limiting factor of reading (Pelli et al.,
2007) and of spatial vision although the precise nature of its underlying mechanisms is still strongly debated (He, Cavanagh, & Intriligator,
1996; Herzog, Sayim, Chicherov, & Manassi,
2015; Intriligator & Cavanagh,
2001; Pelli, Palomares, & Majaj,
2004; Pelli & Tillman,
2008; Saarela, Sayim, Westheimer, & Herzog,
2009; Strasburger, Harvey, & Rentschler,
1991; Strasburger & Malania,
2013; Tyler & Likova,
2007; Wolford,
1975; Yeshurun & Rashal,
2010; Yeshurun, Rashal, & Tkacz-Domb,
2015). Some recent reviews show the difficulty of providing a clear-cut understanding of crowding (Levi,
2008; Strasburger, Rentschler, & Jüttner,
2011). Crowding has also been invoked to account for reading deficits either in amblyopia (Levi, Song, & Pelli,
2007), in low vision (Wallace, Chiu, Nandy, & Tjan,
2013; Wallace, Chung, & Tjan,
2017), or in developmental dyslexia (Martelli, Filippo, Spinelli, & Zoccolotti,
2009) although this remains a controversial issue both in low vision (Bernard, Scherlen, & Castet,
2007; Calabrèse et al.,
2010; Chung,
2004; Scherlen, Bernard, Calabrèse, & Castet,
2008) and dyslexia (Doron, Manassi, Herzog, & Ahissar,
2015; Ramus & Ahissar,
2012).