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:We employed the same design as Dohmen et al. (2010) to measure the mothers‚Äô risk preferences.5
 At the daycare centers, we conducted experiments with the children to obtain behavioral
 measures of their willingness to compete and, as a control variable, their risk attitudes.
Category: