Interesting article. It does not say but I bet the big difference is in how Portal 2 stimulates dopamine. The enjoyment/success with a accomplishing a task causes the dopamine response. This reward stimulates dopamine. When dopamine is stimulated, learning is faster and 'locks' in better. The study was too short to determine if Lumosity would catch up or if it has a broader range of improvements. This dopamine reaction is the same system that causes addiction. The pleasure of the chemical or activity causes the brain to want to repeat that activity (sex is one such activity) or chemical (drugs or alcohol) experience

Something that I have never seen discussed is where the line is between healing or neurogenesis oriented improvements and improvements due to strengthening/improving under-developed skills. Same goes for cognitive therapy. After an injury, the brain develops lazy or stagnant pathways or skills. Therapy can exercise these pathways/skills to strengthen them.