Artificial light at night also makes guppies more courageous during the day, according to a behavioural study led by researchers from IGB and the Max Planck Institute for Human Development. Exposing fish to artificial light at night, not only made fish more active during the night, but also made them emerge quicker from hiding places during the day, which could increase their exposure to predators. Nocturnal lighting, however, did not affect their swimming speed or social behaviour during the day.