You can tell how smart a person is by how fast their iris contracts to light!

About thirty years ago, someone found that the speed with which the iris contracts in response to a flash of light corresponds very closely to the I.Q. Measured by a psychologist using a standard intelligence test.

The devices used to measure reaction time in drivers' education courses also give a good indication of a person's intelligence, but so does measuring their heart rate, or taking their temperature.

Colleges would probably be embarrassed to admit students on the basis of their temperature.

In other words; your body can tell others around you how smart you really are by using it's biological/physiological functions through certain times. So if it takes your iris a long time to contract be proud of yourself! You might be pretty smart!

(Source)