Lies Of P adds 8 new gestures for you to learn during the Overture DLC, and getting all of them unlocks the To Be Human achievement, one of the 11 new achievements introduced. These gestures get unlocked as part of NPC side quests and general exploration, and we have put up here a complete guide to help you out with getting this trophy.
Gesture #1: Play Dead

Just behind the Hall of Adventure Stargazer is a Mammoth exhibit. Behind the exhibit is the Discover Wildlife: Bears! collectible. Read this to unlock the Play Dead gesture.
Gestures #2: Tap Dance, and #3: Cheer

You unlock Tap Dance & Cheer gestures as you complete collecting 4 Carnival Coins in the Carnival Garden area of Lies Of P Overture.
Gesture #4: Doubt
You get the Doubt gesture on interacting with the 3rd Crusher Puppet near the Ergo Mining Site Stargazer as part of the Brain in a Vat sidequest in Lies Of P Overture.
Gesture #5: Heart

The Heart gesture is unlocked on giving Ergo to Rosaura when you meet her at the Pistris Harbor Stargazer in Chapter 3.
Gesture #6: Deep Bow
Start from the Archon Fleet Shipwrecks Stargazer, you will progress in the area going through, well, various shipwrecks. After you exit the 1st Shipwreck, pass the fish suddenly jumping out of the sea, and take the plank into the 2nd Shipwreck.

Once you enter here, before taking the steps to the lower level, take the other route which gets you into an open area, and just before a ladder, will be the ‘Correspondence Beyond the Sea’ collectible. Open this from your inventory, and the Deep Bow gesture gets unlocked.
Gesture #7: Shiver
This is a neat one, you get the Shiver gesture if you die with the Freeze debuff. It can be either from enemies in areas like the Shipwrecks; or from the vents in the platforming section near the Security Area Stargazer.
Gesture #8: Peer Into The Distance
Climb to the very top of the Krat Lighthouse, and when you step outside, a cutscene automatically triggers, getting you the Peer Into The Distance gesture.