<i>It doesn&#x27;t slow anything down.</i><p>That depends.<p>Some readers do what is known as &quot;subvocalization&quot;[1], where they literally speak the words they&#x27;re reading, but silently, actuating the muscles in their tongue and throat as if they were speaking aloud. If you&#x27;re doing that then it <i>does</i> slow you down.<p>[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Subvocalization" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Subvocalization</a>