M.Sc Thesis

M.Sc StudentSabato Sivan
SubjectThe Semantics of Reciprocal Expressions in Natural
DepartmentDepartment of Computer Science
Supervisor MR Yoad Winter


The interpretation of reciprocal expressions such as each other and one another exhibits a remarkably wide variation in different contexts. Specifically, the predicate in the scope of the reciprocal expression affects its interpretation. Consider the following examples of two minimally different sentences with reciprocal expressions:

1.      Dan, John and Mary saw each other

2.      Dan, John and Mary followed each other.

Sentence (1) entails that every person in the specified group saw every other person in the group, while sentence (2) does not entail the analogous claim.

We propose a new formal system for predicting the interpretation of reciprocal expressions in a given context. This system is based on a principle called the Strongest Meaning Hypothesis (SMH) that was proposed in Dalrymple et. al (1998) (henceforth DKKMP) to account for the effect of contextual factors on the truth conditions of different reciprocal sentences. The SMH as formulated on DKKMP chooses the strongest meaning that is consistent with relevant contextual information, out of an independently defined set of meanings for reciprocals.

The system proposed by DKKMP is thus composed of two components: One is the SMH, and the other is the set of meanings the SMH chooses from. The new system we propose is based on the critical observation made in DKKMP about the weakening of the interpretation of a reciprocal sentence by contextual factors. However, unlike DKKMP, we implement the SMH as a mapping from semantic restrictions on the predicate's denotation into the interpretation of the reciprocal, with no independent assumptions about available reciprocal meanings. This new implementation also defines the loose notion of `relevant contextual information' used by DKKMP, and identifies this information solely with a formal concept of semantic restrictions of predicates.

We implement the SMH as a local maximality principle. According to this principle, a reciprocal sentence is consistent with models in which no pairs of non-identical individuals in the antecedent set can be added to the denotation of the predicate, while remaining within its semantic restriction. Our formulation of the SMH allows a systematic analysis of types of predicates and the truth conditions they induce on  reciprocal sentences that contain them. We analyze the connection between semantic restrictions, interpretations of reciprocal sentences, and several meanings that are proposed in the literature for reciprocal sentences.