> They even point this out as a specific point in the abstract: You can't compare kids doing enrichment activities to kids not doing enrichment activities while controlling for every other variable to be the same, because it is manifestly true that time spent on enrichment activities can not be spent on other activities, such as sleep or socializing, which also have benefits.
Please double-check my reading comprehension of your comment. Are you saying that it is not possible to analyze the benefits of enrichment activities as opposed to what normal kids do, because there is no way to have a group of kids who do exactly what normal kids do + enrichment activities, because taking the time to do enrichment activities necessarily knocks out at least one activity normal kids do, thereby making control impossible?
Please double-check my reading comprehension of your comment. Are you saying that it is not possible to analyze the benefits of enrichment activities as opposed to what normal kids do, because there is no way to have a group of kids who do exactly what normal kids do + enrichment activities, because taking the time to do enrichment activities necessarily knocks out at least one activity normal kids do, thereby making control impossible?