In fact, this statement has no scientific basis. Being left-handed is just a habit, just like doing things with your right hand, but the result is the same.
It is precisely because left-handers are uncommon that people regard scarcity as the most precious thing and think that left-handers are smarter. Children don't always hold pens in their right hands when they pick them up. Many of them are left-handed, but they are forced by teachers and parents later.
Not everyone is born with a right hand. Children have no concept of right and left hands. They can use any convenient hand. This is only the use of the body, and it has nothing to do with cleverness.
People often say that left-handed people are smart, but left-handed people don't think so. Cong is not smart because of his brain development, not because of which hand he is used to, but because the flexible use of his hand will make his brain more active.
Whether left-handed or right-handed, the development and memory storage of the left and right brains have their own division of labor. You can't choose which one you want to use, at least scientifically.
The statements of the older generation are all passed on by word of mouth, and there is no basis to prove the authenticity of this sentence so far.