In sign language, nearly all the signs for body parts are made by pointing to the specific body part. For example, 'nose', 'eyes', 'mouth', 'arm', 'hair', 'ear', are all signed by pointing to the specific body part. These body parts represent the meaning of transparent. You will often see a baby point to his various body parts when you ask him/her, ‘Where is your nose? Where is your mouth?” This is an example of the beauty of a language that has signs that are transparent and/or iconic. When the sign actually looks like the meaning of the word, or in this case is the body part, it is easier for a baby to process and comprehend the way language works. So when a baby points to objects or body parts, s/he is actually saying ‘this is my nose’. This is visual transparency.
When a baby learns the sounds that animals make, this is auditory transparency. He actually hears the cat say 'meow' or the dog say 'woof woof', so s/he often assigns those corresponding sounds to those respective animals. Sign language takes these animals and assigns a visual sign that is closely linked to the meaning of the animal, again reinforcing the benefits of learning sign language which may initially consist of many visually transparent or iconic signs.