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 suggest that the interaction of two superimposed stimuli occurs during early sensory processing, while the interaction of two spots or separated patches of dots may occur later in sensory-motor integration or even in the motor pathways for pursuit (e.g., Kahlon and Lisberger 1999).
Category: