Caffeine is an everyday drug which can disturb the human circadian timing system. We investigate whether this effect can be traced back to a change in the circadian processing of light-dark information. In a placebo controlled design, we specifically test if caffeine intake changes pupil size and sensitivity of intrinsically photosensitive ganglion cells. For our research project we are looking for a highly motivated master student with a strong interest in biological psychology, chronobiology and/or sleep research. The master project involves recruitment of participants, data collection (mainly in the evening hours), analyses as well as interpretation of results. Please do not hesitate to contact us in case of any questions. ***Please note that no positions are available at the moment***. PIs: Carolin Reichert and Manuel Spitschan.