system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did we realise the mind is in the brain?
gpt
Most human cultures large enough to have major medical practices or dedicated healers were able to observe that injuries to the brain can cause changes or impairments to the mind. 

It took more studies to get a more precise understanding, but the connection between the mind and the brain is pretty intuitive from just what can be observed.