To sound smart, avoid umming, aahing and filler words

In this video from The Package Boy, he explains (and demonstrates) how avoiding using filler words and umming noises will make you appear smarter to others.

Counterpoint: talking to someone slowly, conspicuously avoiding filler noise is uncanny. If they're watching what they say, they're on the record, and if they're on the record, you're on the record. It's like haggling over customer service, or being talked to by a cop.

Tip! if you are confident of your intelligence, use filler words and umming noises and uptalk to take advantage of people's prejudices about stupidity.