I am not familiar with the marshmallow test? :) I only ate my first marshmallow when I came to American at 20ish years old. Hence it's been  about a couple decades since... But have not eaten many marshmallows since.  

 https://www.simplypsychology.org/marshmallow-test.html 

 Cool. Thx. Now I remember reading up or hearing of this briefly somewhere at some point. Yep... Delayed gratification is at play.