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:…2653
Changes in an animal’s behavior measured in relearning sessions some time after initial learning may reflect effects on many processes, including performance as well as acquisition, consolidation, retention, and retrieval of memory (Abel and Lattal 2001; Cahill et al. 2001; Wang et al. 2006b).
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