The starting point
A memory or reasoning exercise should be judged against the task you actually want to perform. Keep a concrete example outside the training exercise so you can distinguish learning the game from becoming more capable in daily life.
Brain-Training Apps
A brain-training game can provide structured practice in its own tasks. Improved scores may reflect familiarity with those tasks. Evidence from a particular training program, population, or research trial should not be generalized to every commercial app or to prevention of dementia.
If you enjoy a cognitive game, treat it as a chosen activity and track the skill it asks you to practice. To test everyday usefulness, also try an independent task that matters to you, such as remembering the main points of a conversation. Do not infer a clinical benefit from a streak or score.
Keep the claim specific
Improvement on a practiced task does not by itself establish a general increase in intelligence or prevention of cognitive decline. Check the skill that matters in daily life, and keep written support available when remembering accurately is important.
Apply the idea with care
Write two separate reasons for using a game: what you enjoy about it and what you hope it will help you do elsewhere. The first reason may be sufficient on its own. For the second, choose an independent example and check it after a reasonable period of practice. Avoid evaluating benefit only through the score the app controls. If the game becomes expensive, frustrating, or time-consuming, compare it with other activities that serve the same purpose. Choosing enjoyable practice is different from purchasing a promise of general protection against decline.