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:Distractor suppression has previously been shown to strongly affect performance and capacity in both attentional (Bettencourt & Somers, 2009; Pylyshyn, 2006) and VSTM tasks (Vogel et al., 2005; Zanto & Gazzaley, 2009), making it an ideal process to examine the role of resource use across both types of tasks.
Category: