The Psychological Foundations of the Grammar 55
The man has evidence that the woman knows that the painting is a Picasso.
If prior to her utterance he too was certain that the particular painting was
a Picasso, he has evidence of mutual knowledge. Yet direct evidence is far
less convincing in cases where the speaker evaluates rather than refers.
Consider:
(4) A man and a woman are both looking at a painting. The man has admired
the painting for years.
She says as she points at the painting: ‘That Picasso is beautiful’.
It can hardly be said that the man has evidence of mutual knowledge that
he and woman evaluate the painting identically. At best he can strongly
believe that they evaluate the painting in a similar manner; he has evidence
for shared but not for mutual knowledge.
Successful communication occurs in cases, such as (4), where mutuality
of knowledge does not appear to be either feasible or necessary. Therefore,
the obvious conclusion is that successful communication does not rest
on the mutuality of interlocutors’ knowledge. Instead it rests on a lower
standard. Prince (1981: 232) agrees and states that:
The view that says that each individual has a belief-set and that, for
any two individuals, the belief-sets may be overlapping, the intersection
constituting ‘shared knowledge’, [What this book labels mutual know-
ledge] is taking the position of an omniscient observer and is not
considering what ordinary, non clairvoyant humans do when they
interact verbally.She introduces the term assumed familiarity and so explicitly denies that
successful communication requires the guarantee of mutuality. Speakers,
she claims, need merely to be able to hypothesize about their hearers’
belief-states. Lee (2001), who holds an almost identical position, argues
that speakers require shared knowledge or shared belief to enable them to
communicate successfully in the vast majority of speech situations. He
employs data taken from Brown (1995) to support his claim. Two subjects
A and B were given slightly different maps with A required to update B’s
out-of-date map. They were not allowed any visual contact with one other
and so were forced to update the map orally. Lee (2001: 38) argues that A
and B required a limited recursion of three steps to establish that they held
shared beliefs which enabled them to communicate successfully. For the
map to be updated successfully B had to believe that A believed B had