We often speak colloquially about how cognitive (working memory) training is like a workout for your brain.  I think this analogy can be somewhat usefully pushed to illustrate underlying principles.

For example, if one were to go to the gym and train on an upper body exercise (e.g., bench press), the muscle gains will be specific to the exercise — that is, you don’t get much transfer to lower leg muscles.  Similarly, we expect a primary effect of cognitive training to largely improve the trained task, just as normally training gains are specific to practice.

But that’s not all that happens with exercise.  Regular and reasonably intense exercise provides a cardio-vascular improvement that appears to broadly benefit health, including cognitively healthy aging.  This is essentially a secondary effect of the primary muscle exercise and also a smaller effect, which is harder to measure.

Our goal in cognitive training is to try to trigger some sort of global improvement analogous to cardio training.  This might show up as increased cognitive reserve (protection from loss due to aging/dementia) or a general increase in processing speed (which declines during aging across a range of domains).  But it’s a secondary effect to the training task, so we expect it might be smaller and harder to measure.

The current idea is that working memory training may be a good cognitive analog to cardio training in physical exercise.  We use our transfer battery in an attempt to pick up the global improvement in reserve or processing speed.  The specific working memory “muscle” is reasonably likely to be a good one to strengthen since WM capacity is important for problem solving, reading comprehension and long-term memory.  But the core question is if there is a brain analog to cardio training such that a training intervention can provide some of the benefit we know arises from lifetime eduction or occupational complexity.

It seems that sometimes our reviewers are surprised by the non-specificity of our transfer predictions or the lack of a precise description of why our particular training task is best.  To us, different training tasks are like the difference between running, biking or zumba — whatever works best to get you to do your cardio is more important than the specific exercise.  Maybe the physical exercise analogy will help communicate this framing better to keep the research on this moving forward.