From Wikipedia, the criminal mastermind that never was:
At this time a myth was started that Ma Barker ruled the gang with an iron fist, but the facts do not seem to support these claims. It is highly unlikely that criminals as adept as Karpis, and even Ma's sons for that matter, would have listened to her. Karpis later wrote about this subject in his memoirs:
"Ma was always somebody in our lives. Love didn't enter into it really. She was somebody we looked after and took with us when we moved city to city, hideout to hideout. It is no insult to Ma's memory that she just didn't have the know-how to direct us on a robbery. It would not have occurred to her to get involved in our business, and we always made it a point of only discussing our scores when Ma wasn't around. We'd leave her at home when we were arranging a job, or we'd send her to a movie. Ma saw a lot of movies."
Harvey Bailey, another well-known bank robber of the era knew the Barker gang well, and in his autobiography published in the 1970's, he agreed with Karpis, observing that Ma Barker "couldn't plan breakfast", and was certainly no mastermind behind any gang activity. Ma Barker's entire reputation as a criminal mastermind was concoted by Hoover to protect the FBI's public image after federal agents discovered they had killed a 62 year old mother.