This is a passive skill wink When You go to your Skill-interface, the nummerals (0/5 or 1/5, ...) by the skills stays in two colours : the passive and the active, each in a different colour
(but I play on xbox, maybe there is an little different?). And in the "Manual" also are all active skills and next all passive skills written wink

When you have that Mindreading skill from Isobel(?) in Farglow, you can probebly "see" an icon in the dialogscreen to push on or something for mindreading a NPC.

Success!

On 7th of february 2015 : I start a new adventure in the Divinity world of Original Sin,
it's a Fantastic Freaking Fabulous Funny ... it's my All Time Favorite One !