Can working memory actually be improved? I'm skeptical of the claim that brain training (dual-n back) can improve working memory; the improvement seems to be task-specific rather than generalize.

The average human being can only keep 7 things in his or her mind at one time. Brain training claims to be able to increase this capacity, but as said above, I am skeptical. Are there any studies that have have shown that the 7-limit short term memory capacity can be increased? Of course, we can abstract and have an mnemonic stand for seven things, but we are still only holding one thing (the mnemonic) in our minds..
No program has been definitively proven to increase working memory in any generalizable way. 


  The authors conclude that memory training programs appear to produce short-term, specific training effects that do not generalize. Possible limitations of the review (including age differences in the samples and the variety of different clinical conditions included) are noted.However, current findings cast doubt on both the clinical relevance of working memory training programs and their utility as methods of enhancing cognitive functioning in typically developing children and healthy adults.


-Is working memory training effective? A meta-analytic review.