This paper presents the results of an analysis of the activities during manual and robotised piece picking tasks to know and understand the impact of the robotisation. Here, this task is manually realized first and then partially automated with a robot. The activity is described with three indicators. These indicators are computed with image processing and a subdivision of the picking area. The robot has an impact on the activity because its introduction induces a convergence of the subjects to the same activity regardless without of their uses of technologies considering the interaction in this case.