Pink or brown? Humans struggle to identify snail shell shades

They’re neither white and gold or black and blue. But in an optical puzzle akin to The Dress, colourful snails are causing scientists at the University of Nottingham to turn to technology to definitively decide whether some snails’ shells are pink or brown.

The beautifully-hued Cepaea nemoralis - commonly known as grove snails - are found all over Europe in a range of colours, from yellow to pink to brown, with some also having ‘humbug’ style banding patterns.

But new research published in the academic journal Heredity, shows that differences in the way that the humans see and categorise colour, often makes it tricky to be sure about the colour of snail shells, leading to heated debate among scientists.