All evidence indicates that the quality scientists refer to as intelligence, or g, is largely inherited, i.e. genetic. The remainder is usually attributed to early childhood environment and development. By the time you’re old enough to think about this and post on HN you’re probably too old to budge your IQ.
“Smart” can mean educated, wise, skilled, experienced, etc., qualities that generally come from effort, practice, and getting older.
Your brain is as a FPGA, it can be educated, trained, skilled, talented, opportunistic.
Intensive contemplation is scientifically proven to expand your capacity to contemplate.
Getting a PhD requires a minimal standard of such investment. Who are these scientists anyways?
It is scientifically proven that using your brain makes it useful.