I'm aware of backlinking to your own work as a way to increase traffic, but recently came across the claim that hyperlinking to (related) professional sites also increases traffic by increasing SEO. Is this true? Any insight is appreciated.
From my understanding no. Essentially, linking to another article or website you are creating a backlink for them. Linking to an article supposedly adds credibility to your article. Or, is spam. I have no idea how Google knows the difference or how they measure links in an article. I have often wondered. It is apparent it is important because HP moderates them with snipping. And, with Your Money Your Life (YMYL) articles they are asking for supporting links at times.
You can help the HubPages community highlight top quality content by ranking this answer up or down.