This afternoon (Jan 31) Ted Gibson (MIT) will present his work entitled "Language for
communication: Language as rational inference" -- see abstract below.
WHERE: The talk will take place in *Wilson Hall 524.* Wilson Hall is
located at the corner of Huron and Wilcox, across the street from Sid
Smith, and the room is in the basement.
WHEN: *Jan 31*, at *3:10pm*.
A reception in the LIN lounge will follow.
ABSTRACT:
Language for communication: Language as rational inference
Ted Gibson, MIT
Perhaps the most obvious hypothesis for the function of human language is
for use in communication. Chomsky has famously argued that this is a
flawed hypothesis, because of the existence of such phenomena as
ambiguity. Furthermore, he argues that the kinds of things that people
tend to say are not short and simple, as would be predicted by
communication theory. Contrary to Chomsky, my group applies information
theory and communication theory from Shannon (1948) in order to attempt to
explain the typical usage of language in comprehension and production,
together with the structure of languages themselves. First, we show that
ambiguity out of context is not only not a problem for an
information-theoretic approach to language, it is a feature. Second, we
show that language comprehension appears to function as a noisy channel
process, in line with communication theory. Given si, the intended
sentence, and sp, the perceived sentence we propose that people maximize P(s
i | sp ), which is equivalent to maximizing the product of the prior P(si)
and the likely noise processes P(si → sp ). We show that several
predictions of this way of thinking of language are true: (1) the more
noise that is needed to edit from one alternative to another leads to lower
likelihood that the alternative will be considered; (2) in the noise
process, deletions are more likely than insertions; (3) increasing the
noise increases the reliance on the prior (semantics); and (4) increasing
the likelihood of implausible events decreases the reliance on the prior.
Third, we show that this way of thinking about language leads to a simple
re-thinking of the P600 from the ERP literature. The P600 wave was
originally proposed to be due to people's sensitivity to syntactic
violations, but there have been many instances of problematic data in the
literature for this interpretation. We show that the P600 can best be
interpreted as sensitivity to an edit in the signal, in order to make it
more easily interpretable. Finally, we discuss how thinking of language as
communication can explain aspects of the origin of word order. Some
recent evidence suggests that subject-object-verb (SOV) may be the default
word order for human language. For example, SOV is the preferred word
order in a task where participants gesture event meanings (Goldin-Meadow et
al. 2008). Critically, SOV gesture production occurs not only for speakers
of SOV languages, but also for speakers of SVO languages, such as English,
Chinese, Spanish (Goldin-Meadow et al. 2008) and Italian (Langus & Nespor,
2010). The gesture-production task therefore plausibly reflects default
word order independent of native language. However, this leaves open the
question of why there are so many SVO languages (41.2% of languages; Dryer,
2005). We propose that the high percentage of SVO languages
cross-linguistically is due to communication pressures over a noisy
channel. We provide several gesture experiments consistent with this
hypothesis, and we speculate how a noisy channel approach might explain
several typical word order patterns that occur in the world's languages.
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