Curious Kids: why does reading in the back seat make you feel sick?

Why does reading in the back seat make you feel sick? – Jane, aged 10, from Coburg North, Australia.

Hi Jane, your question about why reading in the back seat makes you feel sick is a very good one. The answer has to do with our eyes, our ears and our brain.

Reading in the back seat can make you feel sick because your eyes and ears are having an argument that your brain is trying to settle!

Read more: Curious Kids: Why do our ears pop?

When you’re reading in the back seat, your eyes see that your book is still. Your eyes then tell your brain you are still.

But your ears feel the car is moving. Your ears then tell your brain you’re moving.

How can your ears tell you’re moving?

Your ears don’t just hear, they help with your balance too.

Your ear has three main parts:

• the outer ear is the bit you can see on the side of someone’s head
• the middle ear is your eardrum and some tiny bones and muscles
• the inner ear is the part of your ear that can help with your balance.

Your inner ear contains cells that have hairs sticking out the top. Scientists call these “hair cells”.

Some of these hair cells help us to hear. When sound hits those hair cells, the hairs move and the cells send signals to the brain. Our brains use those signals to hear.

Other hair cells help us to keep our balance. When the car we’re sitting in moves, that movement makes the hairs on those hair cells move too, and they send different signals to the brain. Our brain uses those different signals to tell we’re moving.

Why doesn’t the brain like this?

Some people’s brains don’t like it when their eyes say they’re still but their ears say they’re moving.

When eyes and ears argue like this, the brain can think that something dangerous might be about to happen.

If this happens, the brain can get the body ready to fight or run away (scientists call this the “fight or flight” response).

One of the things the brain can do is take blood away from the stomach to give to the muscles.

Giving blood to the muscles can help us to fight or run away. But taking blood away from the stomach can make us feel sick.

What can you do about it?

If reading in the back seat makes you feel sick, you might need to settle the argument between your eyes and your ears.

One way to do this is to stop reading and to look out the car window. This could help your eyes to tell your brain that you’re moving as you see the world whizz by, and your ears to tell your brain that you are moving as you feel the car moving.

Read more: Curious Kids: Do astronauts get space sick when they travel from Earth to the International Space Station?

But this suggestion won’t work for everyone. Some people will still feel sick when they ride in a car, even if they aren’t reading.

This is because while our eyes and our ears help us to balance, so do our skin and our muscles. This creates many opportunities for arguments that our brain has to settle!

Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.au

Wayne Wilson receives research funding from organisations including the Australian Research Council, the Autism Co-operative Research Centre, Sonova Pty Ltd, and others.