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:Because numerous reports have demonstrated impaired sensory filtering in schizophrenics (Adler et al., 1982; Freedman et al., 1987; Snyder, 1973; Solomon et al., 1981; Sorensen et al., 1993), the results of the present study suggest that activation of 5-HT2 receptors could improve sensory filtering in these individuals.
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