The coordinate systems that the human brain uses to represent objects in space are still under debate. They can be studied by analyzing patients with a lesion in the parietal lobe, since these patients fail to respond to stimuli that are presented contralateral to the brain lesion: a lesion in the right hemisphere leads the subject to ignore the left side of the space. But what is left? We analyze an experiment where neglect patients perform visually guided saccades under different experimental conditions. Determining where neglect patients have longer reaction time and higher probability of errors helps to identify the dominant coordinate system that the brain uses.