I am passing this along without endorsing it (travel prevents me from going through the research):
The n-back task involves presenting a series of visual and/or auditory cues to a subject and asking the subject to respond if that cue has occurred, to start with, one time back. If the subject scores well, the number of times back is increased each round. The task can be done with dual auditory and visual cues, or with just one or the other.
A few years ago, Jonides and his colleagues Martin Buschkuehl, Susanne Jaeggi, and Walter Perrig demonstrated that dual n-back training increased performance on tests of fluid intelligence. But the current work extends that finding in several ways.
“These new studies demonstrate that the more training people have on the dual n-back task, the greater the improvement in fluid intelligence,” Jonides said. “It’s actually a dose-response effect. And we also demonstrate that the much simpler single n-back training using spatial cues has the same positive effect.”
In the so-called real world, who actually gets this kind of training?:
According to Jonides, the n-back task taps into a crucial brain function known as working memory—the ability to maintain information in an active, easily retrieved state, especially under conditions of distraction or interference. Working memory goes beyond mere storage to include processing information.
For the pointer I thank MR commentator JamieNYC.