When it comes to human development, play is as important to the cognitive and communicative growth of children as working and studying is to adults.
During play, children put into practice the schema that they have built. They tap on their creativity by using imagination, creating dialogues, and personifying objects. Along with creativity comes the application of language for specific purposes, this time being for socialization. When children speak to each other, there is always the possibility of learning new words (slang, second language, regular words).
There is also a myriad of different accents, forms of intonation, and diverse uses of language that children share from one another. Through repetition, social learning, scaffolding, and interaction, children greatly expand their language usage. As a result, the cognitive abilities expand as well making it possible for children to apply newly-learned language skills for problem solving, arguments, discussions, and for critical expression.
Although the cognitive ability and low affective filter of children keep their minds in a constant state of learning, it is through play when learning is intensified. Motivation intensifies the application of skills during playtime, sometimes consisting taking turns, deciphering codes, arguing, and making decisions. Therefore, play is extremely important to the cognitive and language acquisition process.
For additional information on play theory read The Encyclopedia of Human Behavior, volume 4 and read on "Variability in Brain Function and Behavior", where the basic principles of play theory and its importance child development are analyzed in full.