According to www.merriam-webster.com hip means "having or showing awareness of or involvement in the newest developments or styles". Or "very fashionable". It seems to me too, the word is more associated with dynamic movement than other words.

If you look at the pictures, in all of them the black people have either a more unique hair style or more dynamically composed picture framing and pose.

I would like to see the results when controlling for such factors as hairstyle, pose, and framing.

Interesting little research project though. Here's the link to it: http://jasoncomely.com/hip/NaturallyHip-Psy-AS1.pdf

I loved "the kid on the left is me".