In her book Radical Candour, on pp. 20-21, Kim Scott (linkedin.com/in/kimm4) relays the following vignette in an interaction with Sheryl Sandberg when Scott and Sandberg both worked for Google.
‘Sheryl laughed, “When you do that thing with you hand, I feel like you’re ignoring what I’m telling you. I can see I am going to have to be really direct to get to you. You are one of the smartest people I know but saying ‘um’ so much makes you sound stupid” ++
Scott’s response to Sandberg’s statement was: