The most interesting people I know are curious people. They're also really smart people.
The correlation between curiosity and smartness may not be causal. But then again, it may.
Those curious-smart people always seem to have an interesting question in mind, and on their lips. Even regarding some of the most mundane subjects/issues, these curious-smart people seem to be searching for a deeper understanding of how things work and how they might be improved upon.
Another attribute of those curious-smart people is that they rarely cast themselves as "smart." They assume they don't yet know enough, and perhaps, could even be wrong in their current thinking/understanding.
I/You/We also know the opposite kinds of characters - the know-it-alls, the dogmatic, the condescending, the non-curious.
Hunger for new learning, and an openness to the possibility of being found to be wrong, seem to be antecedents for real growth. Curiously.