Based on the analysis of spoken narratives about a short film by Sacapultec speakers, Du Bois (1987) examines the phenomenon of ergativity and its relation to surface grammar pattern and information flow, and proposes 'Preferred Argument Structure (PAS)' in grammatical and pragmatic aspects, which extends to accusative type languages. Four proposed grammatical and pragmatic constraints are as follows (A stands for transitive subject, S intransitive subject and O transitive direct object):
'One Argument Constraint': Avoid more than one lexical argument per clause.
'Non-lexical A Constraint': Avoid Lexical A.
'One New Argument Constraint': Avoid more than one new argument per clause.
'Given A Constraint': Avoid introducing new referent in the A-role position.
The present study reexamines these constraints through the analysis of ten friends and ten strangers conversations to investigate how interlocutor relationship interacts with PAS. While the overall results support the robustness of PAS, the analysis reveals how the interlocutors' interactional strategy motivated by the degree of assumed shared knowledge affects the syntactic and pragmatic aspects of their language use as follow:
Strangers conversations involve considerably larger proportion of nominal predicates which are attributed to the beginning parts of the strangers conversations occupied largely by personal/background information exchanges by nominal predicate clauses; Strangers use more intransitive clauses without overt lexical arguments which is due to the strangers' careful choice and development of a topic for the topic to be directly related to/closely developed around the personal/background information obtained from one another; There are statistically more pronominal A's in strangers conversations than in the friends'; The O role's strong tendency toward overt lexical forms, due to its tendency to carry new information, appears to lessen the effect of interlocutor relationship on the choice of the referential forms of O role arguments.