According a report published on Monday's Daily Telegraph, Facebook, video games and Sudoku enhance user's intelligence, whereas Twitter, texting and YouTube actually reduce it.
Dr. Tracy Alloway, a psychologist from the University of Stirling in Scotland, said that Facebook and its expansive networks help humans hone their "working memory," which helps people retain and manipulate information.
The study found Facebook enhances intelligence because the mind has to work in keeping up with friends. It's also extremely diverse: Users can play games, chat with friends, view photos and videos and take tests.
Video games that involve planning and strategy, such as those from the Total War series, may also train working memory, Dr Alloway believes.
"I'm not saying they're good for your socialization skills, but they do make you use your working memory," she said. "You're keeping track of past actions and mapping the actions you're going to take."
Sudoku also stretched the working memory, as did keeping up with friends on Facebook, she said.
But text messaging, micro-blogging on Twitter and watching YouTube were all likely to weaken "working memory."
"On Twitter you receive an endless stream of information, but it's also very succinct," said Dr Alloway. "You don't have to process that information ... Your attention span is being reduced and you're not engaging your brain and improving nerve connections."
Working memory involves the ability both to remember information and to use it. At a job interview, a candidate will employ working memory to match answers to questions in the most impressive way.
Dr. Alloway has developed a working memory training program for slow-learning children aged 11 to 14 at a school in Durham, and she found out that Facebook did wonders for working memory, improving the kids' IQ scores, while YouTube's and Twitter's steady stream of information was not healthy for working memory.
Also, playing video games, especially those that involve planning and strategy, can also be beneficial.
After eight weeks of memory training, the children saw 10 point improvements in IQ, literacy and numerical tests. A number that started off close to the bottom of the class ended up near the top.
"It was a massive effect," said Dr. Alloway, who today gave a talk on working memory at the start of the British Science Festival at the University of Surrey in Guildford.
However, Dr. Alloway also says that if you mix Twitter up with other online activities, there probably won't be any negative effects.
