Asked by: Lorely Maskell, High Wycombe
People who are born blind, or become blind early in life (before around five or seven years of age), do not experience visual imagery when they dream. People who became blind later typically do retain some visual imagery when they dream – but less so than in sighted individuals.
A study by Danish researchers found that the longer someone has been blind, the less likely they are to dream visually. And while those who were born blind may not see in their sleep, they are more likely than those with sight to experience auditory, olfactory, gustatory and tactile components to their dreams.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.