Perceptive

I think this could be balanced by granting a +1 to Wisdom, Expertise in perception checks, and advantage on checks to read expressions. 

As is, it's too powerful.

Yah, always being able to tell if a creature is lying is stupidly strong, and also somewhat hilarious. The Great Wizard Torqual, master of illusion and enchantment magics, weaver of grand tales, can be caught out by a variant human looking at his eyes.

Also there's already a feat called Observant, which is literally a synonym of perceptive.

Here's my attempt to fix this feat:

Shrewd (better fits the description anyway)

Skilled at noticing small details during conversation, you gain the following benefits:

• Increase your Wisdom score by 1, to a maximum of 20.
• You gain proficiency in the Insight skill. If you already have proficiency, your proficiency bonus is doubled for any Insight check you make.
• You have advantage on any check you make to discern whether a creature is telling the truth.