People and gestures
Signs on different cultures can coincide under the form, but differ under the contents.
In Ancient Rome, deciding destiny of the won gladiator, spectators expressed the will gestures. The thumb, downy downwards, meant death won, and lifted upwards - mercy.
This gesture - a finger upwards - was saved in many cultures, and in ours including, but it means other - perfectly!
The Nod a head instead of the answer to a question is used by the different people, including relatives on language Bulgarians and Russian. When the Russian person nods, it means "yes" when shakes a head - "is not present". At Bulgarians all on the contrary: they slightly throw back a head back as a sign of negation, and shake a head when agree. Imagine that to you there has on a visit arrived the Bulgarian who is perfectly speaking Russian, but not possessing Russian sign system. You ask it: you Want to tea?. That in the answer winds a head. Well it is fine, - you speak and continue conversation, and your friend for some reason takes offence.
Unlike sound language, the sign language comprises the universal, universal moments. But nevertheless the large part of signs exists within the limits of this or that culture.