Facebook insiders have admitted that it is. Mike Allen, Facebook's first president, said this in an interview:
“The thought process was all about, ‘How do we consume as much of your time and conscious attention as possible?’,” he said. “And that means that we need to sort of give you a little dopamine hit every once in a while, because someone liked or commented on a photo or a post or whatever, and that’s going to get you to contribute more content, and that’s going to get you more likes and comments. It’s a social validation feedback loop. … You’re exploiting a vulnerabilty in human psychology.”
So that underscores their general attitude towards user behavior. The 'every once in a while' piece applies to the newsfeed too - it's designed to keep you searching for things you care about, and they carefully mix in things you don't, so that you're never too satisfied or unsatisfied, just constantly craving more.