There are things the world doesn’t need. The banana slicer, for example, when a knife gets the job done just fine, or shoes for babies. For generations of linguists, filler words have fallen into the same category. The common belief is that they add little to a dialogue aside from making the speaker sound nervous (“uh”), juvenile (“like”) or insecure (“sort of”). Yet, verbal fillers are a major part of how we talk, featuring in virtually every spoken sentence. Humanity tends to bend toward efficiency, so why would we collectively persist in wasting our breath on “ums” and “ahs”? 

A recent strain of research has sought to prove that filler words can help hold a conversation. In 2017, dozens of language experts from this new school of thought challenged The New York...