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:Our results are also consistent with those of recent studies of how experimentally conditioned aversive stimuli inhibit instrumental approach behavior (Geurts et al., 2013; Huys et al., 2011), which have been modeled as competing valuation systems in RL models (Dayan et al., 2006; Guitart-Masip et al., 2012, 2014; Huys et al., 2011).
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