Unmarked and Markedness
According to UG there are certain innate principles in human mind, by which a child gradually develops its language. The principles that are universal and most common are known as core grammar and the uncommon rules are known as the periphery. But the core grammar is unmarked.
Related to the concepts of core and periphery is Chomsky’s theory of markedness .Core rules are unmarked ,that is, they accord with the general tendencies of language .Periphery rules are marked ;that is, they are exceptional in some way.Thus ,the adjectives big,long,and fast are unmarked in relation to small,short,and slow,because they occur in both declarative and interrogative sentences ,while the latter occur only in the declarative sentences.
UG is maximally relevant to the core elements that can be described through its principles and parameters ,such as Binding Theory and pro-drop, minimally relevant to other aspects of language such as constructions ’the more the merrier’.The elements that do not fit into the system of UG are considered as peripheral. Outside the core grammar, the set of "peripheral" or marked properties of a language include exceptions or relaxations of the settings of core grammar and the idiosyncratic features of the language governed by particular lexical items.
The principles and the parameters are not aquired from outside since they are already present as part of our UG inside the mind.The principles and parameters are not itself sufficient to create language.They have to be ’triggered ’ by something in the language input the child hears.This is seen predominantly as caused by positive evidence-things that actually present in the input.So,the word order parameters for English(SVO) may be triggered by hearing sentence such ’Lucy reads a book”.The role of language input is therefore to trigger the appropriate setting for each parameter.So,the setting for the parameters is a must. There might be no initial setting, so a child who begins to learn a language can adopt any setting with equal ease. Or there might be a default setting consisting of one or other of the possible settings. Two possible settings are non-pro-drop and pro-drop settings.
Setting can be of two kinds namely initial default setting and the learnt setting called ’markedness’.The initial setting is said to be the unmarked setting;the setting that can be learnt through experience is marked.