Recent research reveals certain types of brain training can increase brain size. The hippocampus volume can affect mood, hedonic setpoints, some forms of memory. A smaller hippocampus has been linked to depression and dysthymia. Certain activities and environmental factors can reset the hedonic setpoint and also grow the hippocampus to an extent. London taxi drivers' hippocampi grow on the job, and the drivers have a better memory than those who didn't become taxi drivers. In particular, the posterior hippocampus seemed to be the most important for enhanced mood and memory.