“…Rather, most stimuli do not contain such features (i.e., response-unrelated stimuli). Previous studies have demonstrated NCEs with response-unrelated stimuli, including simple nondirectional stimuli (e.g., horizontal and vertical lines, squares and diamonds, and bidirectional arrows; Boy & Sumner, 2010; Eimer, 1999; Schlaghecken et al, 2007) and more complex, realistic stimuli (e.g., pictures of different emotional faces or hands; Bennett, Lleras, Oriet, & Enns, 2007; Vainio, 2011; Vainio et al, 2013). The occurrence of NCEs with response-unrelated stimuli might be due to the strengthening of their S-R associations through practice.…”