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:In a follow-up experiment Pascalis 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…
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