Pupil sizes can therefore be used to read people because it gives us a reliable tool for measuring interest and arousal even if in a subtle way. Subconsciously we are all aware of other’s pupil sizes as indicated by the research. Paying at least some conscious attention to the pupil sizes of others can give us information about the overall state the people around us are in. One of the reasons pupil size is so powerful is because we are not able to consciously control the size of our pupils which means that pupils will always naturally react to stimuli we find attractive. Wearing sunglasses by professional poker players is partially explained with these findings since dilated pupils might provide a ‘tell’ to their opponents.