**2. Definition of brain training**

The wider cognitive intervention field abounds with multiple ill-defined terms that have hampered their development and validation, and can also explain mixed findings to date (Gates & Valenzuela, 2010). Clare and Woods divide this general area into 'cognitive rehabilitation', 'cognitive stimulation', or 'cognitive training' (CT) (Clare & Woods, 2004). We have proposed a specific operational definition for cognitive training (CT) to include cognitive interventions that meet the following four criteria: 1) involves repeated practice, 2) on tasks with an inherent problem, 3) using standardized exercises, and 4) that specifically target a cognitive domain (Gates & Valenzuela, 2010) . Here, the terms BT and CT are identical and are used interchangeably.
