Research from the Brain Imaging Centre at Goethe University has revealed that we see better at dawn and dusk – times when our distant ancestors would have been most at risk from predators in the shadows.

In a study, 14 men were asked to spot a dim flashing light at different times of day. The results at 8am and 8pm were far better than any other time of day. By scanning their brains around the 8pm test time, neuroscientists found that the brain is able to shut down background visual “noise” in the visual cortex at this time – exactly when cavemen would have needed to be able to spot predators in reduced light.

Conversely, the study also revealed that human eyesight is worst at 2pm. The researchers point out that the difference is not in what the men saw through their eyes, but in their visual perception, which is controlled by the brain.

Sources:

1. Science Daily:
   Optimized perception in the twilight zone.