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:…et al. (2005) examined the plasticity of infants’ discrimination of monkey faces by providing 6-month-olds with folders containing pictures of six unfamiliar monkey faces where parents were asked to show these pictures to their infant for 1–2 min each day (see Pascalis et al., 2005, p. 5298).
Category: