develop throughout writing development. The generative principle incorporates the idea that a writer can create new meanings by organizing units of writing and letters of the alphabet. The sign principle is understanding that the word print also involves paper arrangement and word boundaries. And lastly, the inventory principle is the fact that children have the urge to list and name items that they are familiar with, and because of this they can practice their own writing skills. More recent research has also explored writing development. Myhill concentrated on the development of written language skills in adolescents aged 13 to 15. Myhill discovered that the more mature writer was aware of the shaping of text, and used non-finite clauses, which mirrored Perera's results (1984). Other researchers focused on writing development up until late adolescence, as there has been a limited research in this area. Chrisite and Derewianke recognize that the survey conducted by Perera (1984) is still one of the most significant research studies in the writing development field and believe Perera's study is similar to theirs. Chrisite and Derewianke (2010) again propose four phases of writing development. The researchers believe that the process of writing development does not stop when an individual leaves formal education, and again, the researchers highlight that these phases are flexible in their onset. The first phase focuses on spoken language as the main aid for writing development, and the development then takes its course reaching the fourth phase, which continues beyond formal education. Environmental influences The environment a child develops in has influences on language development. The environment provides language input for the child to process. Speech by adults to children help provide the child with correct language usage repetitively. Environmental influences on language development are explored in the tradition of social interactionist theory by such researchers as Jerome Bruner, Alison Gopnik, Andrew Meltzoff, Anat Ninio, Roy Pea, Catherine Snow, Ernest Moerk and Michael Tomasello. Jerome Bruner who laid the foundations of this approach in the 1970s, emphasized that adult "scaffolding" of the child's attempts to master linguistic communication is an important factor in the developmental process. One component of the young child's linguistic environment is child-directed speech (also known as baby talk or motherese), which is language spoken in a higher pitch than normal with simple words and sentences. Although the importance of its role in developing language has been debated, many linguists think