The theory believes that mental representation has both a combinatorial syntax and compositional semantics. The claim is that mental representations possess combinatorial syntax and compositional semantic—that is, mental representations are sentences in a mental language. Alan Turing's work on physical machines implementation of causal processes that require formal procedures was modeled after these beliefs. Another prominent linguist, Steven Pinker, developed this idea of a mental language in his book The Language Instinct (1994). Pinker refers to this mental language as mentalese. In the glossary of his book, Pinker defines mentalese as a hypothetical language used specifically for thought. This hypothetical language houses mental representations of concepts such as the meaning of words and sentences. Scientific hypotheses The Sapir–Whorf hypothesis in linguistics states that the grammatical structure of a mother language influences the way we perceive the world. The hypothesis has been largely abandoned by linguists as it has found very limited experimental support, at least in its strong form, linguistic determinism. For instance, a study showing that speakers of languages lacking a subjunctive mood such as Chinese experience difficulty with hypothetical problems has been discredited. Another study did show that subjects in memory tests are more likely to remember a given color if their mother language includes a word for that color; however, these findings do not necessarily support this hypothesis specifically. Other studies concerning the Sapir-Whorf hypothesis can be found in the "studies" section below. Chomsky's independent theory, founded by Noam Chomsky, considers language as one aspect of cognition. Chomsky's theory states that a number of cognitive systems exist, which seem to possess distinct specific properties. These cognitive systems lay the groundwork for cognitive capacities, like language faculty. Piaget's cognitive determinism exhibits the belief that infants integrate experience into progressively higher-level representations. He calls this belief constructivism, which supports that infants progress from simple to sophisticated models of the world through a change mechanism that allows an infant to build on their lower-level representations to create higher-level ones. This view opposes nativist theories about cognition being composed of innate knowledge and abilities. Vygotsky's theory on cognitive development, known as Vygotsky's theory of interchanging roles, supports the idea that social and individual development stems from the processes of dialectical interaction and function unification. Lev Vygotsky believed that before two years of age, both speech and thought develop in differing ways along with differing functions. The idea that relationship between thought