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:…shown distractor suppression to have a much larger effect on capacity than target selection processes (Bettencourt & Somers, 2009; Pylyshyn, 2006; Vogel et al., 2005; Zanto & Gazzaley, 2009), and as the effect on capacity of increasing the number of distractors is correlated between VSTM and MOT…
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