Almost! The "-" symbol, when appearing as a singular symbol, is a hyphen and connects word elements. To be used as in the example, it should be used as "--", which is called a dash. Capitalization is not required for the phrase directly following the dash.

"Imagine that we are in a world where humans never developed the ability to speak -- how would society look?"
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence