In my cold reading experiment, I (likely correctly) guessed that you, my reader, are closest to your maternal grandmother out of all your grandparents.
This was a gimme. Studies have consistently shown that people are closest to their maternal grandmother.
Why?
There are three logical reasons.
First, since women live longer than men, people are likely to have more time on earth with their grandmothers than their grandfathers.
Second, women stay in more frequent contact with their parents, especially their mothers, than men do with theirs, and are likely to live closer to their parents throughout life. This gives maternal grandparents an edge in seeing their grandchildren more often.
Third: Cuckoldry. The maternal grandmother knows absolutely 100% that her daughter is hers, and knows absolutely 100% that her grandchild is her daughters. None of the other grandparents have this luxury. The maternal grandfather may have been cuckolded by his wife. The paternal grandmother knows her son is hers, but her son may have been cuckolded by his wife. The paternal grandfather has it particularly bad. He may been cuckolded and/or his son may have been cuckolded. Grandparents instinctively adjust their bonds towards grandchildren based on cuckoldry risk. This isn’t a choice, it just happens.
Both of my grandfathers were dead before I was born, my paternal grandmother died when I was less than 5, so maternal grandma won by default. She taught me my first swear word (by accident) and for that I am fucking grateful.