What can "to scratch the itch" in different meanings?

Question

Having a song, tune, or commercial jingle stuck in one's head is a phenomenon known as having an earworm. Most people have had an earworm at one time. The experience is harmless and unrelated to both obsessive-compulsive disorder and endomusia, the hearing of music that is not really there. Certain songs – simple, repetitive, or oddly incongruous – have properties that act as mental mosquito bites in that they produce a cognitive "itch." The condition also arises when people struggle to remember forgotten lyrics or how a song ends.

What does the next phrase (in bold) mean in other words?

To scratch a cognitive itch, the brain repeats the song, which then traps the hapless victim in a repeated cycle of itching and scratching. Everyone has his or her own list of demon tunes that haunt.

_{Source: Discover Magazine}

Answer 1

Anyone who has had a rash or mosquito bite knows what it's like to have a strong urge to scratch it. Even when you're told that scratching it will only make it worse (such as with a scabbing wound), it can still be hard to keep your fingernails away.

The word itch, though, can refer to a figurative itch as well as a literal one. The word itch can be defined in several ways, but a few notable ones include:

• (n.) An irritating skin sensation causing a desire to scratch
• (n.) A restless desire or craving for something: an itch to travel
• (n.) An uneasy longing or propensity; a teasing or tingling desire: an itch for praise
• (v.) To have a persistent, restless craving.

The words itching and scratching often go hand-in-hand. For example, a musician might have a sudden itch to play some music; sitting down at the piano or picking up a guitar could "scratch that itch" by soothing or fulfilling the desire.

In the case of a cognitive itch – the phrase used in your article – that would be a figurative itch inside the mind. The author is suggesting that the person with the earworm has a strong urge to hear the song (or at least play it in their mind). Succumbing to that itch and "scratching it" (in the case of the earworm, that would mean singing or humming the song) would bring it back to the forefront of your mind, which gives to the desire to hear it again, thus producing a vicious cycle and keeping the earworm stuck in place.

Answer 2

As Jeff Morrow mentioned, the phrase is being used as a pure metaphor here, and it's even explained. The song gets stuck in your head and metaphorically "itches." You mentally "scratch" it by replaying it, which means it is still stuck in your head, so you are in a cycle.

The expression is often used idiomatically to mean "satisfy a craving." For example if I said "I have a craving for chocolate, so I'm going to scratch the itch," it would mean I'm going to eat some chocolate.