Selectional restrictions

Lexical entries also contain information about the roles assigned to the nouns in a clause. For instance, build and calculate assign Agent role to their subject noun and Patient role to their direct object noun. In (8), Romans is Agent and aqueduct is Patient, and in (9) computer is Agent and value is Patient.

The fact that aqueduct is inanimate does not change the assignment of Patient role to it, and likewise the inanimacy of computer does not change the assignment of Agent role. Picking up the concept of the central, prototypical member of a class, we can say that prototypical Agents are animate, or even human. Inanimate nouns such as computer can be non-prototypical Agents, the role being thrust upon them by particular verbs and particular constructions. For instance, calculate requires an Agent, and in the ACTIVE DECLARATION construction the Agent role is assigned to the noun to the left of the verb.

Lexical verbs impose restrictions on the type of noun that can occur to their left or right. A verb such as blame requires a human noun to its left, while a verb such as kill requires an animate noun to its right. Of course, speakers and writers regularly utter sentences such as (10) and (11).

Speakers and writers who produce (10) know perfectly well that blame is assigned by moral beings; they merely assume that dogs qualify. In our treatment of (11), we continue to state that kill requires an animate noun to its right. The clash between this requirement and the fact that proposal is inanimate imposes a metaphorical interpretation.

Constraints affecting the type of lexical noun are known as selectional restrictions. Selectional restrictions range from large classes of nouns such as animate and human nouns (shorthand for ‘nouns denoting animate beings’ and ‘nouns denoting human beings’) to smaller classes such as nouns denoting liquids. For example, the verb flow requires a subject noun such as water, river or lava, as in (12).

This particular verb raises two interesting points. The first is that, as with (10) and (11), the verb can be used metaphorically; we talk of ideas flowing from someone’s pen. The second is that a given noun on its own may not denote a liquid but may be understood as doing so because of its modifiers. Thus The molten metal flowed into the mould does not require a metaphorical interpretation, but the fact that the metal is liquid is contributed by the adjective molten. This last example is handled in the same way as (11). Even without the adjective molten, it imposes the interpretation that the metal was in a liquid state and forces us to construct a suitable context, for example a foundry