When you first start learning to read, you read aloud. This helps make the text easier to understand.
After that, you start mumbling, whispering, or just moving your lips as you read. But as reading skills improve, all of this disappears. Eventually you start reading silently to yourself.
And the so-called inner voice arises when you read to yourself. When a person thinks to himself rather than out loud, it is called inner speech.
If reading skills are well developed, it will be much easier and faster for you to read to yourself rather than aloud. You’re going to hear your inner voice right now, and that’s pretty common. One study found that 4 out of 5 people reported hearing an inner voice often or always while reading to themselves.
Another study showed that this inner voice can change depending on what you read. Experts also believe that there are many types of inner voices: the voice can be your own or have a completely different timbre.
Source: Ferra

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