I recall that your confounder was used as an explanation to wave away the air reproducibility of the marshmallow test, but I do not recall anyone actually ever

I recall that your confounder was used as an explanation to wave away the air reproducibility of the marshmallow test, but I do not recall anyone actually ever testing that. This recent article seems to indicate that it's all just horse feathers and so you can make up any confounder you want to explain it away...