Proto-roles
Dowty (1991) proposed a solution to some of the problems with thematic roles. The first component of Dowty’s solution was the suggestion that the different participant roles ‘are simply not discrete categories at all, but rather are cluster concepts, like the prototypes of Rosch and her followers’ (1991: 571; on prototypes, see 7.1.3). What this means is that the boundaries between different roles are fuzzy: an argument isn’t classified as either an Agent or, say, an Instrument; instead, it’s classified as more or less Agent-like. The prototypical nature of the thematic role types explains why it is hard to assign each argument neatly to a single role: a single argument, like the subject of roll in (11) above, can have both Agent-like and Theme-like aspects at the same time. Because the boundaries between roles are fuzzy, it’s expected that there should be these sorts of effects.
The second aspect of Dowty’s proposal was that thematic roles are based on entailments of verb-meanings. A verb’s entailments are those propositions that must necessarily be true whenever the verb itself is true (see 6.6.1). For example, consider the subject argument, Gavrilo, and the verbs murder, nominate and interrogate, in (16):
These verbs share the following entailments:
• VOLITION: Gavrilo acted volitionally;
• INTENTION TO PERFORM THE ACT NAMED BY THE VERB: Gavrilo intended to murder, nominate or interrogate the Archduke; these weren’t things that just happened as a side-effect of what he was doing;
• CAUSATION: Gavrilo caused some event to take place that involved the Archduke; and
• MOTION OR EXTERNAL CHANGE: Gavrilo either moved or changed in some external (i.e. not just mental) way in performing the action.
Note the affinity of these entailments with our definition of Agent, the ‘initiator of the action’. In standard accounts of linking, Gavrilo would be classified as an Agent in all three contexts. Not all subject arguments, however, share these entailments. Dowty gives the following verbs as examples:
• volitional action isn’t an entailment of kill (traffic accidents kill without being volitional)
• intending to perform the act named by the verb isn’t shared by convince (I can convince you without intending to convince you, even though I am intending to speak)
• causation isn’t shared by look at
• motion or external change isn’t shared by understand
These arguments lack some of the Agent entailments, but they are still treated as subject. Dowty proposed that only two role-types are needed to account for linking. He called these role-types Proto-Agent and Proto Patient. Each proto-role is identified by a number of properties. The more of these properties a verb’s argument entails, the more it belongs to the appropriate proto-role. The properties for the two roles are as follows:
Contributing properties for the Agent Proto-Role:
a. volitional involvement in the event or state
b. sentience (and/or perception)
c. causing an event or change of state in another participant
d. movement (relative to the position of another participant)
e. exists (independently of the event named by the verb)
Contributing properties for the Patient Proto-Role
: a. undergoes change of state
b. incremental theme
c. causally affected by another participant
d. stationary relative to movement of another participant
e. does not exist (independently of the event named by the verb) (Dowty 1991: 572)
Incremental theme is a new term due to Dowty (1991) and Krifka (1987). The object NPs in (17) are examples:
The key to the idea of Incremental theme is that the verb’s object is pro gressively – ‘incrementally’ – affected by the action of the verb as the event unfolds. Building a house, for example, happens over a certain period of time, with the house getting more and more built with each passing day. Similarly, a letter gets more and more written as I write it, the sandwich more and more eaten as the eating progresses, and so on. To see how much has been built, written, or eaten we need only compare the house, the letter or the sandwich at two different points in time during the event. The verb, in other words, affects the theme ‘incrementally’. Examples of non-incremental themes would be the objects of achievement predicates like reach the top, shoot the target, and so on (see 9.2.2.2).
QUESTION Can you think of any examples in which the subject (instead of the object) is the incremental theme?
As we have seen, the entailments are independent of each other – not every verb has everyone. Dowty (1991: 572) gives the following examples of the independence of the Proto-Agent entailments:
Dowty points out, however, that build has all subject and all object entailments.
QUESTION Can you find equivalent sentences showing the independence of the Proto-Patient entailments?
The full solution to the linking problem may already be clear to you. Dowty suggests that the argument with the most Proto-Agent entailments will be coded as subject, and the one with the most Proto-Patient entailments as object. This principle has two related corollaries. First, it’s possible for some arguments to share the same role, have neither role, or qualify partially but equally for both proto-roles. Second, if two arguments satisfy roughly the same number of Proto-Agent and Proto-Patient entailments, then either may be coded as subject or object. This is the case for psych verbs such as Joe likes sausages/Sausages please Joe: in this situation, regardless of how it is described, both participants have just a single entailment each: Joe has the proto-agent entailment of sentience, and sausages has the proto agent entailment of causation. Dowty says that neither argument has any other entailments. This means that each argument has equal likelihood to surface as subject.
The same explanation accounts for other doublets like Fabienne lent Briony a book/Briony borrowed a book from Fabienne. We can see this in the following table:
