Brains
'Brains' is a Stat that represents your intelligence and book-smarts. It can help you feint and avoid feints in combat.
Medic, Hack, Repair, Science, Linguist, Chemistry, and Teach are all skills that rely solely on Brains, checking no other stat.
The Brains stat is also used feint in combat.
When your Brains stat falls below a certain point you will get a filter which can impair your speech.
Where to train
Read wikipedia in the matrix. Or find a certain computer deep below slagtown.
Skills that depend on Brains
Appraise
Bombs
Chemistry
Craft
Hack
Linguist
Locksmith
Medic
Persuade
Pilot
Repair
Science
Teach