There is a strong relationship between language development and symbolic play. A tendency that develops as early as age three, symbolic play is the use and manipulation of objects to represent others during play. The application of this type of thinking entails the beginning of what is known by Watson & Jackowitz (1984) and Weininger & Fitzgerald (1988) as "representational thought". This also implies the development of metacognitive thinking. According to Piaget, the developmental stage where most symbolic play takes place is the pre-operational stage particularly the symbolic function substage that manifests from years 2-4.
This being said consider the additional fact that language development achieves its highest momentum within an individual's lifespan during the first three years of life. Here we have two separate developmental processes occurring at the same time: Representational thinking and language development at a pre-operational age.
Hence, during the application of symbolic play there are ubiquitous opportunities for language usage.The combination of both, along with the socialization that begins to take place at around age 4 in Head Start or Pre-Kindergarten solidifies both processes. Children play make-believe games using a specific language for the specific game. Development and expansion are the results of this kind of interaction. Therefore, the cognitive process that leads to symbolic play develops in tandem with the neurological and cognitive processes that enable language acquisition. When put in a social context, one is interdependent on the other.