system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we have reflexes of gag when brushing tongue with toothbrush?
gpt
The gag reflex is a involuntary reaction to having large objects in or near the back of your throat (note that large is a relative term, here). The body has this reflex to help keep you from choking when it senses something that it thinks would be too large to swallow. The gag reflex ideally expels the object from your throat, and you live to learn to chew your food better.

The gag reflex is unique from person to person. Some people don't have much of one, while others' is very sensitive to the point where eating something sticky like peanut butter will trigger it.