1. They're highly self-aware.

Intelligent people are constantly aware of how they're being perceived by the world around them. They're always thinking about how other people are seeing them, if they're blending into a crowd, or if they're standing out. This is also a common feature of socially anxious behavior.

2. They have high sentinel intelligence.

Sudden loud noises can send socially anxious people into an immediate panic. If they hear a loud noise, while others are simply still processing the noise, they're already thinking about what the noise was. It may seem excessively nervous but it's actually a great survival technique.