Theta role
Encyclopedia
In generative grammar
(in particular Government and binding theory
and the Standard Theory of Transformational Grammar), a theta role or θ-role is the formal device for representing syntactic argument structure
(the number and type of noun phrases) required syntactically by a particular verb. For example, the verb put requires three arguments (i.e., it is trivalent
). The formal mechanism for implementing this requirement is based in theta roles. The verb put is said to "assign" three theta roles. This is coded in a theta grid associated with the lexical entry for the verb. The correspondence between the theta grid and the actual sentence is accomplished by means of a bijective filter on the grammar known as the Theta Criterion
. Early conceptions of theta roles include (Fillmore called theta roles "cases") and .
One common way of thinking about theta roles is that they are bundles of thematic relations associated with a particular argument position.
The other notation (see for example the textbook examples in and ) 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., , 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.
When applied to the sentence [S[NP Susan]i gave [NP the food]j [PPto Reggie]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. 's formulation is:
Although it is often not explicitly stated, adjuncts are excluded from the theta criterion.
F-structures are further constrained by the following two constraints which do much of the same labor as the θ-criterion:
(HPSG) (for a textbook introduction see ) does not use theta roles per se, but divides their property into two distinct feature structures. The number and category are indicated by a feature called ARG-STR. This feature is an ordered list of categories that must cooccur with a particular verb or predicate. For example the ARG-STR list of the verb give is. The semantic part of theta roles (i.e. the thematic relations) are treated in a special set of semantic restriction (RESTR) features. These typically express the semantic properties more directly than thematic relations. For example, the semantic relations associated with the arguments of the verb give are not agent, theme and goal, but giver, given, givee.
and the Simpler Syntax Model
(see also Jackendoff's earlier work on argument structure and semantics, including and ) claim that theta roles (and thematic relations) are neither a good way to represent the syntactic argument structure of predicates nor of the semantic properties that they reveal. They argue for more complex and articulated semantic structures (often called Lexical-conceptual structures) which map onto the syntactic structure.
Similarly, most typological approaches to grammar, functionalist theories (such as Functional Grammar
and Role and Reference Grammar
, and Dependency Grammar
do not use theta roles, but they may make reference to thematic relations and grammatical relations
or their notational equivalents. These are usually related to one another directly using principles of mapping.
Generative grammar
In theoretical linguistics, generative grammar refers to a particular approach to the study of syntax. A generative grammar of a language attempts to give a set of rules that will correctly predict which combinations of words will form grammatical sentences...
(in particular Government and binding theory
Government and binding theory
Government and binding is a theory of syntax and a phrase structure grammar in the tradition of transformational grammar developed principally by Noam Chomsky in the 1980s...
and the Standard Theory of Transformational Grammar), a theta role or θ-role is the formal device for representing syntactic argument structure
Verb argument
In linguistics, a verb argument is a phrase that appears in a syntactic relationship with the verb in a clause. In English, for example, the two most important arguments are the subject and the direct object....
(the number and type of noun phrases) required syntactically by a particular verb. For example, the verb put requires three arguments (i.e., it is trivalent
Valency (linguistics)
In linguistics, verb valency or valence refers to the number of arguments controlled by a verbal predicate. It is related, though not identical, to verb transitivity, which counts only object arguments of the verbal predicate...
). The formal mechanism for implementing this requirement is based in theta roles. The verb put is said to "assign" three theta roles. This is coded in a theta grid associated with the lexical entry for the verb. The correspondence between the theta grid and the actual sentence is accomplished by means of a bijective filter on the grammar known as the Theta Criterion
Theta Criterion
In syntax, the theta criterion states that in a grammatical sentence, every theta role that a verb can assign must be realized by some argument, and each argument may bear only a single theta role...
. Early conceptions of theta roles include (Fillmore called theta roles "cases") and .
Theta roles and thematic relations
The term Theta Role is often used interchangeably with the term thematic relations (particularly in mainstream generative grammar — for an exception see ). The reason for this is simple: theta roles typically reference thematic relations. In particular, theta roles are often referred to by the most prominent thematic relation in them. For example, a common theta role is the primary or external argument. Typically, although not always, this theta role maps to a noun phrase which bears an agent thematic relation. As such, the theta role is called the "agent" theta role. This often leads to confusion between the two notions. The two concepts, however, can be distinguished in a number of ways.- Thematic relations express the semantic relations that the entities denoted by the noun phrases bear towards the action or state denoted by the verb. By contrast, Theta roles are a syntactic notion about the number, type and placement of obligatory arguments. For instance, in the sentence Fergus ate the kibble, the fact that there are two arguments (Fergus and the kibble) and Fergus must be capable of volition and doing the action and the kibble must be something that can be eaten is a fact about theta roles (the number and type of the argument). The actual semantic type of the argument is described by the thematic relation.
- Not all theoretical approaches use theta roles. Theta roles are largely limited to the Chomskyan versions of Generative grammar and Lexical-functional grammar. Many other approaches such as Functional Grammar, and dependency grammar refer to thematic relations directly without an intermediate step in theta roles.
- Only arguments of the verb bear theta roles; optional adjunct modifiers — even if they are prepositional phrases (PPs) such as on Friday or noun phrases (NPs) like "yesterday" — don't take theta roles. But almost all NPs (except expletiveSyntactic expletiveSyntactic expletives are words that perform a syntactic role but contribute nothing to meaning. Expletive subjects are part of the grammar of many non-pro-drop languages such as English, whose clauses normally require overt provision of subject even when the subject can be pragmatically inferred...
s) express thematic relations. - An argument can bear only one theta role, but can take multiple thematic relations. For example, in "Susan gave Bill the paper." Susan bears both Agent and Source thematic relations, but it only bears one theta role (the external "agent" role).
- Thematic relations are properties of nouns and noun phrases. Theta roles can be assigned to any argument including noun phrases, prepositional phrases and embedded clauses. Thematic relations are not assigned to embedded clauses, and prepositions typically mark the thematic relation on an NP.
One common way of thinking about theta roles is that they are bundles of thematic relations associated with a particular argument position.
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 and ) 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., , this box also contains information about the category associated with the theta role. This mingles theta-theory with the notion of subcategorization
Subcategorization frame
In syntax, a subject within linguistics, the subcategorization frame of a word is defined to be the number and types of syntactic arguments that it co-occurs with...
. 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 [S[NP Susan]i gave [NP the food]j [PPto Reggie]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
Theta Criterion
In syntax, the theta criterion states that in a grammatical sentence, every theta role that a verb can assign must be realized by some argument, and each argument may bear only a single theta role...
(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
Deep structure
In linguistics, specifically in the study of syntax in the tradition of generative grammar , the deep structure of a linguistic expression is a theoretical construct that seeks to unify several related structures. For example, the sentences "Pat loves Chris" and "Chris is loved by Pat" mean...
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. '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.
Thematic hierarchies
Drawing on observations based in typological cross-linguistic comparisons of languages , linguists in the relational grammar (RG) tradition (e.g. observed that particular thematic relations and theta roles map on to particular positions in the sentence. For example, in unmarked situations agents map to subject positions, themes onto object position, and goals onto indirect objects. In RG, this is encoded in the Universal Alignment Hypothesis (or UAH), where the thematic relations are mapped directly into argument position based on the following hierarchy: Agent < Theme < Experiencer < Others. Mark Baker adopted this idea into GB theory in the form of the Uniformity of Theta Assignment Hypothesis (or UTAH) . A different approach to the correspondence is given in and , where there are no such things as underlying theta roles or even thematic relations. Instead, the interpretive component of the grammar identifies the semantic role of an argument based on its position in the tree.Lexical-functional grammar (LFG)
Lexical-functional grammar (LFG) ( and is perhaps the most similar to Chomskyan approaches in implementing theta-roles. However, LFG uses three distinct layers of structure for representing the relations or functions of arguments: θ-structure, a-structure (argument structure) and f-structure (functional structure) which expresses grammatical relations. These three layers are linked together using a set of intricate linking principles. Thematic relations in the θ-structure are mapped onto a set of positions in the a-structure which are tied to features [+o] (roughly "object") and [±r] (roughly "restricted" meaning it is marked explicitly by a preposition or a case marking). Themes map to [-r], second themes map to [+o] and non-themes map to [-o]. These features then determine how the arguments are mapped to specific grammatical functions in the sentence. The first [-o] argument is mapped to the SUBJ (subject) relation. If there is no [-o] argument then the first [-r] argument is mapped to the SUBJ relation. If neither of these apply, then you add the plus value ([+r] or [+o]) to the feature structure and apply the following mappings: [-o,-r]: SUBJ, [+o, -r]: Object (OBJ), [-o,+r]: prepositional marked oblique (OBLθ), [+o, +r]: prepositionally marked object (OBJθ). These mappings are further constrained by the following constraints:Function argument biuniqueness Each a-structure role corresponds to a unique f-structure function, and each f-structure function corresponds to a unique a-structure role
The Subject Condition Every verb must have a SUBJ
F-structures are further constrained by the following two constraints which do much of the same labor as the θ-criterion:
Coherence requires that every participant in the f-structure of a sentence must be mentioned in a-structure (or in a constituting equation) of a predicate in its clause.
Completeness an f-structure for a sentence must contain values for all the grammatical functions mentioned in a-structure.
Head-driven phrase structure grammar (HPSG)
Head-driven phrase structure grammarHead-driven phrase structure grammar
Head-driven phrase structure grammar is a highly lexicalized, non-derivational generative grammar theory developed by Carl Pollard and Ivan Sag. It is the immediate successor to generalized phrase structure grammar. HPSG draws from other fields such as computer science and uses Ferdinand de...
(HPSG) (for a textbook introduction see ) does not use theta roles per se, but divides their property into two distinct feature structures. The number and category are indicated by a feature called ARG-STR. This feature is an ordered list of categories that must cooccur with a particular verb or predicate. For example the ARG-STR list of the verb give is
Approaches that eschew theta roles
Many approaches to grammar including construction grammarConstruction grammar
The term construction grammar covers a family of theories, or models, of grammar that are based on the idea that the primary unit of grammar is the grammatical construction rather than the atomic syntactic unit and the rule that combines atomic units, and that the grammar of a language is made up...
and the Simpler Syntax Model
Simpler Syntax
Simpler Syntax is the title of a 2005 book by Peter Culicover and Ray Jackendoff. The authors argue that modern minimalist syntax is going in the wrong direction, adopting ever more complex structures and derivations, and making overly strong assumptions about linguistic universals. Richard Kayne's...
(see also Jackendoff's earlier work on argument structure and semantics, including and ) claim that theta roles (and thematic relations) are neither a good way to represent the syntactic argument structure of predicates nor of the semantic properties that they reveal. They argue for more complex and articulated semantic structures (often called Lexical-conceptual structures) which map onto the syntactic structure.
Similarly, most typological approaches to grammar, functionalist theories (such as Functional Grammar
Functional grammar
Functional theories of grammar include a range of functionally based approaches to linguistics, the scientific study of language. The grammar model developed by Simon Dik bears this qualification in its name, functional grammar, as does Michael Halliday's systemic functional grammar.Role and...
and Role and Reference Grammar
Role and reference grammar
Role and Reference Grammar is a model of grammar developed by William Foley and Robert Van Valin, Jr. in the 1980s, which incorporates many of the points of view of current functional grammar theories....
, and Dependency Grammar
Dependency grammar
Dependency grammar is a class of modern syntactic theories that are all based on the dependency relation and that can be traced back primarily to the work of Lucien Tesnière. Dependency grammars are distinct from phrase structure grammars , since they lack phrasal nodes. Structure is determined by...
do not use theta roles, but they may make reference to thematic relations and grammatical relations
Grammatical function
In linguistics, grammatical functions refer to functional relationships between participants in a proposition...
or their notational equivalents. These are usually related to one another directly using principles of mapping.
See also
- Morphosyntactic alignmentMorphosyntactic alignmentIn linguistics, morphosyntactic alignment is the system used to distinguish between the arguments of transitive verbs and those of intransitive verbs...
- Valency (linguistics)Valency (linguistics)In linguistics, verb valency or valence refers to the number of arguments controlled by a verbal predicate. It is related, though not identical, to verb transitivity, which counts only object arguments of the verbal predicate...
- Case grammarCase grammarCase Grammar is a system of linguistic analysis, focusing on the link between the valence, or number of subjects, objects, etc., of a verb and the grammatical context it requires. The system was created by the American linguist Charles J. Fillmore in , in the context of Transformational Grammar...
- Lexical mapping theory, a theory of the possible mappings between thematic roles and syntactic functionsGrammatical functionIn linguistics, grammatical functions refer to functional relationships between participants in a proposition...
- Thematic relations