Dr. Alloway has developed a working memory training programme 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 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.
As with any such study, one needs to take the results with a grain of salt. Without going into the benefits of training working memory for improving your IQ results, it's obvious that Facebook and Twitter are hard to compare. Facebook is extremely versatile: you can play games there, chat with your friends, view photos and videos; you can even take IQ tests.
Twitter is a much simpler, more streamlined service. Does that fact alone makes it detrimental to your working memory? Dr. Alloway claims: "On Twitter you receive an endless stream of information, but it's also very succinct. 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.'' That may be true, and while looking at Twitter like a zombie for the better part of the day is probably bad for you, if you mix it up with other online activities - such as Facebook - I doubt you'll see any negative effects.