Anyway, the basic finding is summed up nicely in the study text:
The results suggest that viewers who orient to The Daily Show as news, or as a mix of news and entertainment, activate greater mental resources than those who orient to The Daily Show as purely entertainment.So, to put it another way, it depends on how you approach the program. This is not unlike a small body of work I've cited myself that argues one reason many people don't learn all that much from TV news is that they approach the medium as "easy" and relaxing, while they approach print as "hard" and requiring more mental effort. The result is obvious. Greater mental effort, greater learning. As an aside, the less educated or interested do tend to learn something from TV news, in part because of the way stories there are structured as opposed to traditional print articles.
Here, this study published in Mass Communication & Society suggests much the same effect for late-night comedies. It all depends on why you watch.