“…The associative nature of GCS has led researchers to posit the involvement of a learning component in the development of synaesthetic associations (for review see Rothen and Meier (2014)). This has prompted a number of studies to investigate whether it is possible to train non-synaesthetic individuals to develop synaesthesia-like experiences (Arend, Yuen, Ashkenazi, & Henik, 2022;Bor, Rothen, Schwartzman, Clayton, & Seth, 2014;Colizoli, Murre, & Rouw, 2012;Colizoli, Murre, Scholte, & Rouw, 2017;Colizoli et al, 2016;Meier & Rothen, 2009;Rothen, Schwartzman, Bor, & Seth, 2018;Rothen, Wantz, & Meier, 2011). Two previous studies of this kind revealed dramatic plasticity in human visual perception by showing that the majority of participants in the first study (Bor et al, 2014), and all participants in the second study (Rothen et al, 2018) reported phenomenology suggestive of GCS.…”