Seven plus or minus two has been a staple of Cognitive Psychology since Miller published a paper on the limitations of short-term memory in the fifties, which led to the naive theory (not endorsed by Miller himself!) that human short-term memory consists of seven (plus or minus two) slots in which items can be stored. But even though cognitive psychologists have abandoned this theory for decades, it still floats around in the applied domain as a serious limitation of human cognition.
To get back to the original topic, I always find ToDo lists quite useful. From a multitasking perspective they perform a very useful service, helping you keeping track of your uncompleted goals. So now this blog claims that these lists do not work, because your brain can only handle seven uncompleted goals.
The cited research for this claim is a set of studies that show that people want choices, but not too many of them. Being able to choose between 3 brands of detergent is nice, but choosing between 20 brands is ridiculous. So, what's the threshold? Seven. Really seven? In many situations I'd rather not choose at all, that is why I like house brands in supermarkets. Maybe in a restaurant I prefer some more choices on the menu than just seven.
But even if this were all true, the generalization from choosing between similar candidates for a purchase and which item to do next on a ToDo list is pretty far-fetched. And the idea that your brain will overheat if the length of your ToDo lists exceeds the threshold is pretty ludicrous.
To conclude: I think ToDo lists are pretty useful as a memory aid. But maybe the lesson is to be really, really suspicious about any type of psychological advice that involves the number Seven. Plus or Minus Two.