Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:The capacity to monitor error performance, as reflected in ERN/Ne amplitude, is thought to rely predominantly on intact ACC functioning (Botvinick et al., 2001; Carter et al., 1998; Gehring and Knight, 2000; Holroyd and Coles, 2002; Luu et al., 2000; Ullsperger and Von Cramon, 2003).
Category: