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:To assess whether distractor size manipulations also affected hand transport control, the maximum tangential velocity of the wrist marker in the plane of the work surface, a conventional and sensitive index of hand transport was also calculated (Gentilucci et al. 1991; Jakobson and Goodale 1991).
Category: