Cognitive Scientist and Harvard Professor, Steven Pinker's revised edition of The Language Instinct: How the Mind Creates Language (P.S.) Provides a thorough treatment of his argument that humans are hard wired for the acquisition of language in the early stages of life. Learning spoken and signed language after this early stage is difficult and the person will often be not as fluent as a native speaker.
Children will also improve on a language such as pigeon English developed by their adult parents. The children will develop a creole of this language incorporating more sophisticated parts of speech. And parents should avoid beating themselves up over the way their children talk. They have very little influence other then controlling their child's exposure to their peers.
He describes as failures the attempts at teaching other animals American Sign Language. Assessments of the animals by hearing individuals were much more charitable than the assessment of a deaf person who is more familiar with the signs. We should not expect these other animals to adopt our form of communication as it would be difficult for humans to communicate using the natural communication style of a non-human primate.
He singled out parrots and dogs as being fairly good communicators. My dog listens well to specific commands and communicates his desire to go for a wall by picking up his lease and dragging it to the back door. My cats adopt there own style of selective listening, but are fairly clear in communicating their demands.
Professor Pinker dismisses many urban legends about language acquisition and expresses boredom at the pronouncement that indigenous people of Northern Canada have multiple words for snow. That is the equivalent of saying that a typesetter has many words to describe fonts or that a mycologist has many words to describe different types of fungi.
Linguistics as a tool to understanding the brain - 50 minutes