system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do we “hear” our voices in our heads?
gpt
Like many things to do with the mind, brain, and consciousness. We're not completely sure.  
MRI scans show that the area of the brain used for language and social interaction lights up when we do it, along with a bunch of other areas.  
So essentially it turns on the parts of the brain used for talking, without actually talking.  
Studies of deaf people who never learned a sign language shows that they have serious trouble learning.     
Which might suggest that the brain might be offloading processing steps to the areas used for talking to do additional thinking.  
But it's all still very speculative.