Theta Grids and The Theta Criterion
Theta roles are stored in a verb's theta grid. Grids typically come in two forms. The simplest and easiest to type is written as an ordered list between angle brackets. The argument associated with the external argument position (which typically ends up being the subject in active sentences) is written first and underlined. The theta roles are named by the most prominent thematic relation that they contain. In this notation, the theta grid for a verb such as give is <agent, theme, goal>.
The other notation (see for example the textbook examples in (Haegeman 1994) and (Carnie 2006)) separates the theta roles into boxes, in which each column represents a theta role. The top row represents the names of the thematic relations contained in the theta role. In some work -- e.g., (Carnie 2006), this box also contains information about the category associated with the theta role. This mingles theta-theory with the notion of subcategorization. The bottom row gives a series of indexes which are associated with subscripted markers in the sentence itself which indicate that the NPs they are attached to have been assigned the theta role in question.
| Agent source DP |
theme DP |
goal PP |
| i | j | k |
When applied to the sentence i gave j k] the indices mark that Susan is assigned the external theta role of agent/source, the food is assigned the theme role, and to Reggie is assigned the goal role.
The theta criterion (or θ-criterion) is the formal device in Government and Binding Theory for enforcing the one to one match between arguments and theta roles. This acts as a filter on the D-structure of the sentence. If an argument fails to have the correct match between the number of arguments (typically NPs, PPs, or embedded clauses) and the number of theta roles, the sentence will be ungrammatical or unparseable. (Chomsky 1981, p. 36)'s formulation is:
The theta criterion Each argument bears one and only one θ-role, and each θ-role is assigned to one and only one argument.
Although it is often not explicitly stated, adjuncts are excluded from the theta criterion.
Read more about this topic: Theta Role
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