Volume of signing isn&#x27;t totally unrelated - even if you presume 4 hours of signing time per day, most people don&#x27;t speak&#x2F;sign for that long an amount of time. It&#x27;s more than a typical deaf person, any way you slice it.<p>But, you&#x27;re right - the manner of signing has something to do with it as well, and I&#x27;ve amended my comment to reflect that. :)