This is a passive skill

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
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!