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ERP indices of referential informativity in visual contexts
Elli Tourtouri, Francesca Delogu & Matthew Crocker
Saarland University
Introduction
Over-specification: more information than required for referent identification
Ubiquitous in language use [1]
Detrimental [2] or beneficial [3] to comprehension?
Under-specification: less information than required for referent identification
Leads to comprehension difficulty [4] and communicative failure
As detrimental to comprehension as explicit referential failure (mismatch)?
ERP study testing the effects of over- & under-specification on visually-situated
language processing
Hypotheses: (1) over-specification facilitates (or does not hinder) comprehen-
sion – speakers would unlikely over-specifiy, if it did. (2) under-specification
hinders comprehension, but possibly not in the same way as explicit referen-
tial failure.
(a) Minimally-specified (MS) (b) Over-specified (OS)
(c) Under-specified (US) (d) Mismatch (MM)
Figure 1: Sample item. The instruction "Find the yellow bowl" is paired with each of
the four displays (conditions).
Materials
Factor manipulated: Informativity
Conditions: minimally-specified (MS), over-specified (OS), under-specified
(US), mismatch (MM)
Item = spoken instruction (in German) + 4 displays (Fig.1)
Distinguishing features: colour or pattern
Only same-gender objects in the display
Counterbalanced target type, position, colour & pattern
Filler descriptions: 0 or 2 modifiers, always MS
Latin square design
Method
32 items per condition, 128 fillers
33 native German speakers
Trial: preview (3s) →fixation cross (500ms) →instruction →wrap-up screen
(500ms) →task
Task: indicate which side of the screen the target object appeared on (OS, MS)
or whether such a decision was not possible (US, MM)
EEG recorded from 26 Ag/AgCl active electrodes (10-20) system with BrainAmp
amplifier (Brain Products)
Analyses performed on -200–1000ms averaged epochs time-locked to adjec-
tive and noun onsets
Planned pairwise comparisons between conditions (OS, US, MM vs. MS)
Predictions: we expected (1) OS to modulate an N400-like component – OS be-
ing less negative than MS, (2) US to yield a component related to processing dif-
ficulty – possibly qualitatively different from MM
Results
Adjective
No significant differences for OS & MM vs. MS
US vs. MS: broad positivity starting around 400ms, more pronounced on right
electrodes
Noun
Graded N400-like effect: OS < MS < MM
US vs. MS: positivity sustained from adjective region through 800ms post-
noun
Figure 2: ERP waveforms time-locked to the onset of the adjective.
Discussion
The graded N400-like effect reflects the visually-determined predictability of
the noun
OS →reduced N400
Over-specification is beneficial to language comprehension
Referential failure due to US is qualitatively different from explicit referential
failure (MM)
The adjective is redundant but also unhelpful (it identifies two objects of the
same type)
Update of mental model of what is being said [5]: (1) general expectancy for
disambiguating information to come in before the noun, or (2) formulation of
specific predictions as to what the next adjective should be, given information
so far
References
[1] Deutsch W. & T. Pechmann (1982). Social interaction and the development of definite descrip-
tions. Cognition, 11, 159-184.
[2] Engelhardt, P. E., S. B. Demiral, & F. Ferrreira (2011). Over-specified referring expressions impair
comprehension: An ERP study. Brain and Cognition, 77, 304-314.
[3] Arts, A., A. Maes, L. Noordman, & C. Jansen (2011). Overspecification facilitates object identi-
fication. Journal of Pragmatics, 43, 361-374.
[4] Engelhardt, P. E., K. G. D. Bailey, & F. Ferrreira (2006). Do speakers and listeners observe the
Gricean Maxim of Quantity. Journal of Memory and Language, 54, 554-573.
[5] Hoeks, J. C. J., L. A. Stowe, P. Hendriks, & H. Brouwer (2013). Questions Left Unan-
swered: How the Brain Responds to Missing Information. PLoS ONE, 8(10), e73594.
doi:10.1371/journal.pone.0073594.
March 19-21, 2015 28th CUNY Conference on Human Sentence Processing | University of Southern California E-mail: elli@coli.uni-saarland.de
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