: In the present work we observe two subjects interacting in a collaborative task on a shared environment. During the experiment we measured the task completion time under two different conditions: either one interactant is wearing dark glasses and hence his/her gaze is not visible by the other one or no interactant is wearing dark glasses. The results show that if one subject wears dark glasses while telling the other subject the position of a certain object, the other subject needs significantly more time to locate and move this object. Hence, eye gaze