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:Previous studies have demonstrated that shorter exposures can disrupt recall performance due to incomplete encoding of the memory array, resulting in increases in both swap errors and guessing (Bays et al., 2009, 2011; Emrich & Ferber, 2012).
Category: