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:That is, experience can maintain an existing ability (Pascalis et al., 2005), but research is needed that examines whether, and under what conditions, experience leads to the ‘‘re-emergence’’ of perceptual discrimination of previously unfamiliar faces of another species once perceptual narrowing…
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