Scratch the cat's back gently. Why does the cat shake its head and stick out its tongue?

There may be several explanations for the cat's behavior of shaking its head and sticking out its tongue. First of all, cats may feel very comfortable and relaxed while enjoying scratching, so they will show slight reactions, such as shaking their heads and sticking out their tongues. This is a normal physiological reaction, similar to the sound that humans make when they feel comfortable.

Secondly, cats may shake their heads to balance their bodies. The cat's inner ear has a set of structures called vestibular organs, which are responsible for controlling the body balance. Scratching will stimulate these organs, and cats may shake their heads to adjust their balance.

Finally, the cat's tongue plays an important role in licking fur and cleaning the body. Scratching the cat's back gently may cause reflex movement of the cat's tongue, resulting in the tongue sticking out. This is also a natural reaction to help cats lick and scratch.