Why our eyesight is best at dusk and dawn: The brain evolved to be sharper at times of low light

  • People see best at 8pm, when twilight falls, and 8am, in the hours after dawn
  • This is when ancestral humans were most at risk of nocturnal predators
  • Brain shuts down activity in other regions to focus on identifying objects
  • There was up to 26% less activity in certain brain regions at dusk versus midday
  • Human eyesight is worst at 2pm, when it is less able to identify flashing objects  

It is the darkest time of the day, when it should be hardest to see properly.

But our eyesight is best at dusk, a study has found, because of human beings’ caveman roots.

We see best at 8pm, when twilight falls, and at 8am, in the hours after dawn, according to an experiment.

Before lightbulbs were invented, these were the times when humans were most at risk from nocturnal predators and needed to be able to keep a look-out.

Neuroscientists from Goethe University in Frankfurt found 14 men asked to spot a dim flashing orange cross against a black background, finding they were best able to do so at 8am and 8pm. Our eyesight is best at dusk, a study has found, due to human beings’ caveman roots.

Cavemen’s brains evolved to spot lions and other predators  

Scanning their brains, they discovered the brain improves vision at these times by shutting down background activity in the visual cortex, so it can process the weak signal from a dimly-lit object better.

The study’s co-author, Dr Christian Kell, from the Brain Imaging Center at Goethe University, said: ‘Driving at dusk and dawn may be easier than it should be because the brain has this mechanism to change our perception of light.

‘This makes sense because it would have helped us to survive as ancient humans by perceiving, for example, a lion in the Savannah.

Read more: http://www.dailymail.co.uk/health/article-5599775/Why-eyesight-best-dusk-dawn-brain-evolved-sharper-times-low-light.html#ixzz5CMvbH8kg

Source: Daily Mail

 

On