When you create your character in The Outer Worlds, you will be given a choice between 15 different aptitudes, which can be a bit of a daunting thing to choose from when you first boot up the game. The choices are very minor, but can make a small different in the way your character responds to certain situations, so it's nice to choose an aptitude that suits your play style.
But what can you do if you chose the "wrong" aptitude? How can you change your aptitude in The Outer Worlds? The unfortunate answer is that it is currently impossible to change your aptitude, no matter what you do. Not even a visit to the Vocational Competence Respecification Machine to reset your Skill and Perks will allow you to change your aptitude.
So, the only method to actually changing your aptitude is to create a completely new character. It's not a good solution at all, but it's the only way. Other than that, just learn to live with the "wrong" aptitude. They don't really have a big effect anyway.