Body Language
Defaults: Detect Lies-4 or Psychology-4.
This is the ability to interpret a person's facial expressions and body posture in order to gauge his feelings. You can use it like the Empathy advantage or Detect Lies skill, but only on a subject you can see. You can also use it to get a rough idea of what a party member is doing or about to do in a situation where he cannot communicate with you directly (for instance, when using Stealth). You can only observe one subject at a time.
The ability to read body language in combat is a standard part of any Melee Weapon or unarmed combat skill; see Feint.
Modifiers: All Vision modifiers; physiology modifiers (below); +4 if your subject is Easy to Read. Anything that makes the subject harder to "read" gives a penalty: baggy clothing gives -1, a shield or a voluminous cloak gives from -2 to -4, and a mask gives -5 (and makes it impossible to use this skill if you cannot see the rest of the body!).
Physiology Modifiers
The following skills deal with the health, function, or vital points of living beings: Body Language, Diagnosis, First Aid, Physician, Pressure Points, Pressure Secrets, and Surgery. These skills work as written when working with members of your species. When dealing with a member of another species, apply the following modifiers:
Species with similar physiology: -2 (human vs. Elf) to -4 (human vs. troll).
Species with very different physiology, but still from your world: -5. This includes all normal animals.
Utterly alien species: -6 or worse (GM's option).
Machine: No roll possible! These skills do not work at all on creatures with the Machine meta-trait.
A successful roll against a suitable skill lets you avoid these penalties. This roll is usually against the relevant racial specialty of Physiology, although Biology-4 suffices for common animals.