[Jensson]

Answering quickly or thinking deeply first doesn't have much to do with intelligence, some smart people answer quickly and other thinks first. It mostly have to do with how much you care about being right, if you are deeply afraid of being wrong you will think a lot first before answering since you prefer spending all that energy over being wrong, while if you don't care you just answer now and think later.

Speaking before you think makes you look dumb, but it doesn't make you dumb. You see the difference? You might have met many such people who were smart, but that you identified as dumb since they weren't afraid of appearing dumb.