Does brain training make you smarter?
Ever since research first demonstrated that mental training can influence brain structure, the brain has frequently been compared to a muscle; exercise makes it stronger, while inactivity makes it weaker. As a result, the commercial brain-training industry is booming. But does brain training really make you smarter?

The possibility that mental training may improve any abilities beyond the skills that are practiced is frequently discussed among neuroscientists. On the one hand, some studies indicate that undertaking one type of training may enhance performance on other types of tasks; [1,2,3] this is known as transfer of training effects. Based on such findings, it has been suggested that the same neural brain networks may be involved in performance across many different mental tasks.[4] In this way, practicing one specific skill may lead to more general performance improvements.
On the other hand, a number of studies show little or no evidence of such transfer effects, indicating that most types of mental training mainly improve the specific skill being practiced. [5,6,7,8.9] For example, if you practice a memory strategy, it is likely that you will improve your performance on tests where you can apply that strategy. You will not necessarily perform better on any type of intelligence test, nor will your general ability to encode, store and recall memories automatically improve. However, as you have learned a new way to make use of your memory, you may manage to apply this strategy to a number of situations. If so, you could say that you are now able to memorise things more effectively in general, as a consequence of the training.

Mental training can help you improve specific skills, but it does not necessarily make you smarter in general. Transfer effects are not yet fully understood, and many researchers are skeptical of how brain-training games are marketed (see for example a Consensus on the Brain Training Industry from the Scientific Community). However, brain-training games do often introduce learning techniques that can be highly efficient, and may thus provide clever ways for you to use your abilities. Read more about memory-strategy training here!
References
4. Klingberg, T. (2010). Training and plasticity of working memory. Trends Cogn Sci, 14(7), 317-324.