The person speaking slowly may be trying to get something important right.

Pace and content are unrelated, though we tend to hear them as connected. A slow speaker gets read as uncertain or unprepared, when frequently the opposite is true and they are choosing words carefully because the subject deserves accuracy. Filling the pause, finishing the sentence, or nodding them along faster costs you exactly the part they were working hardest to get right.

Let the next silence run a few seconds longer than feels natural. When somebody speaks slowly, assume care rather than confusion, and wait for the end of the thought before offering yours.