Discussion: Yawning is designed to lower the "gear of the brain" to save energy and help metabolism.

The accepted explanation for yawns, which also exist in fetuses and the animal world, is that yawning is intended to cool the brain.

It was initially thought that yawning was intended to pump more oxygen into the lungs, but this theory was wrong. The explanation that yawning is intended to cool the brain indirectly is quite proper, but the answer is incomplete and does not provide a broad view.

If the explanation that yawning is intended to cool the brain were the full explanation, then when we have a high fever, we would yawn endlessly. However, yawning usually lasts a few seconds and cannot significantly cool the brain. Lowering the brain's gear takes loads off it and indirectly cools it down, but the original explanation, accepted in the literature, is incomplete.

Our brain is constantly occupied with a subconscious activity that consumes many resources. (Not just calories)
The need to "lower a gear" exists when the brain detects a situation in which it is not working effectively.

Yawning happens, especially when we are bored or tired. A completely different mechanism explains its contagious nature. We tend to imitate others to save valuable brain resources. If you see someone yawning and feel bored, you will probably imitate the action without activating a thought mechanism, an energy grabber.

Link: Yawning is meant to slow down the brain to free up energy for metabolic activity.
https://www.sf-healing.com/blog/post/207 (Copy & Paste)