I am writing a story where humankind has made contact with aliens, and has been spending some weeks trying to establish meaningful communication.
These are the characterisrics of the aliens that I find relevant to the question:
- They are not humanoid. They resemble more a naga or a Starcraft hydralisk than a human. When standing tall, adults will vary in height from 3 to 9 feet (heights vary throughout population in a bell curve).
- They are not able to vocalize. They are not deaf, but compared to a human, they are hearing impaired.
- They communicate among themselves through a complex mix of skin color and texture changes, pheromones, body signs, and a hand sign language of their own.
- Their intelligence range is exactly like our own. Some are great minds who would be compared to our famous philosophers, inventors and professors; Some others would be contenders for the Darwin Awards. Most are as smart as the next human, though.
- Their technology level is bronze age. They have not developed writing on their own, but they can paint and draw.
Most importantly: they have articulated arms and hands. Their arms have two elbows. Their hands have zygodactyl fingers, that is, four fingers disposed like the toes of a woodpecker:
In a way, all of their fingers are opposable thumbs. The aliens are dexterous, according to this definition from dictionary.com:
skillful or adroit in the use of the hands (...)
Last but not least, they naturally have four arms each - but in some tribes they rituallistically tear one arm from each side off, so that the remaining arms and hands get more agile as a compensation.
With all these conditions in mind, I would like to have the aliens communicating with the humans through sign language.
The aliens are smart enough to understand the American Sign Language should they be taught. But would their arm/hand configuration allow them to express themselves by using ASL, and if so, would they be able to use it without limitations? I.e.: would they have the ability to express ideas in ASL without any constraints caused by their anatomy?
I am willing to accept an answer that says the aliens would not be effective at all at using ASL if it makes a sensible point - as a fallback for my history, humans can learn to interpret the aliens' sign language too.
Edit: one reason I would have for the aliens to be able to use ASL, even if in limited or modified form, is so that the aliens would have the possibility to learn it and communicate with humans who have never had any contact with the alien language before. They would be able to contact a human newcomer and say "We can understand you, the other humans taught us".