Sleep is a mysterious thing. For a long time, we weren’t sure why we do it. Now we know that sleep has evolved for multiple reasons – to allow the body to heal and to clean our brains of toxins, for example.
We also know that animals sleep for the same reasons. But why exactly do we dream, and do animals dream, too?
- What is sleep and why do animals need to sleep?
- Researchers spent 455 days and nights watching orangutans sleep – what they observed was very human
Dreams help to strengthen memory. The more we dream, the better our memories are. But it is also thought that dreams ‘train’ us how to respond to different situations – not just situations we’ve already been exposed to, but also those that we might one day face.
By experiencing new situations in our dreams, we apply what we’ve learnt in our everyday lives to new contexts, and this may make us better able to respond well.
We know we dream because we can talk about our mysterious night-time adventures. Figuring out whether animals dream requires a bit more creativity.
Most of us have watched a dog, cat, rat or bird twitching in their sleep, and these movements are likely to indicate dreaming.
But the absence of movement does not mean the absence of dreams. Many wild animals may have evolved not to move too much in their sleep in case it attracts predators.
How do we know if animals are dreaming?
Scientists have started looking at brain activity. When sleeping animals have brain activity that mirrors wakeful brain activity, this indicates they are dreaming.
This hasn’t been studied in a huge number of animals, but dream-like brain activity has been detected in quite a few species, including rats, monkeys and octopuses.
By looking in detail at brain activity during sleep, scientists can figure out exactly what animals are dreaming of. Neuronal activity in dreaming rats suggests they dream about specific places – for example, mazes they’ve explored while awake.
And not only that, they might even walk those routes in reverse and imagine new routes in their dreams, too.
We still have a lot to learn about dreaming, but some dream scientists think that dreaming in animals is a sign of sentience. This suggests that many species have rich inner lives that we are only just beginning to understand.
