More and more evidence is pointing in the direction that bilingualism is good for the Brain. What this means is that understanding and acting on both verbal and nonverbal clues as we age becomes increasingly difficult. Hence, learning a new language increases mental flexibility by exercising the part of the brain that manages Flow in the Words of Mihaily Csikszentmihalyi.
For another perspective, tune into the Los Angeles Times!
Try also the Flow-Evolution game on Cognitive Labs game page...