Modeling stress assignment in English
noun-noun compounds:
a quantitative perspective
Gero Kunter, Ingo Plag, Sabine Lappe & Maria Braun
Universität Siegen
Conference Quantitative Investigations in Theoretical Linguistics 2, 1-2 June 2005, Osnabrück
The problem
• compounds in English are stressed on the left-hand member (e.g.
bláckboard, wátchmaker).
• nuclear stress rule vs. compound stress rule (Chomsky and Halle
1968:17)
• many unexplained exceptions, and cross-variety variation (e.g. BrE vs.
AmE)
Boston márathon
summer níght
may flówers
Penny Láne
aluminum fóil
silk tíe
In general:
• claims on compound stress are largely based on anecdotal evidence
and introspection
• no systematic large-scale empirical evidence available yet
Three approaches
1. The structural hypothesis
(e.g. Giegerich 2004, Bloomfield 1933, Lees 1963, Marchand 1969 or Payne/Huddleston 2002)
• modifier-head structures are regularly stressed on the RIGHT
constituent (steel brídge)
• argument-head structures are always LEFT-stressed (ópera singer)
• left stress on modifier-head structures is due to lexicalization
(ópera glasses)
2. The semantic hypothesis
(e.g. Fudge 1984, Ladd 1984, Liberman and Sproat 1992, Olsen 2000, 2001)
stress assignment according to semantic categories
3. The analogical hypothesis
(e.g. Schmerling 1971, Liberman and Sproat 1992, Plag 2006)
stress assignment in analogy to similar compounds in the lexicon
Testing the hypotheses
• Plag (2006, experimental study):
all three types of factor interact in compound stress
assignment in complex ways.
• this paper: corpus study testing the three hypotheses more
thoroughly
-
many more different word types
many more tokens
many more semantic relations
computational modeling of analogical effects
• Data
- Boston University Radio Speech Corpus (Ostendorf et al. 1996)
(N = 4410, V = 2476, AmE)
- CELEX lexical data base (Baayen et al. 1995)
(N = 4491, V = N, BrE)
Boston Corpus: Example
The device is attached to a plastic wristband
. It looks like
a watch. It functions like an electronic probation officer
.
When a computerized call is made to a former prisoner's home
phone
wristband
, that person answers by plugging in the device. The
can be removed only by breaking its clasp, and if
that's done the inmate is immediately returned to jail. The
description conjures up images of big brother watching. But Jay
Ash, deputy superintendent
of the Hampton County jail in
Springfield, says the surveillance system
sinister.
is not that
Procedure
(cf. Farnetani et al. 1988, Ingram et al. 2003, Plag 2006)
Step 1
Measure mean fundamental frequency (F0) of the main stressed
vowels of the two members, respectively, and calculate the
difference (left F0 minus right F0, logarithmically transformed
into semitones (ST), ’pitch difference‘)
wrístband
+5.39 ST
home phóne
-0.97 ST
Step 2
Look for statistically significant pitch differences between distinct
kinds of compound
Example:
Left-headed compounds (such as attorney géneral) should have a
significantly smaller pitch difference than right-headed compounds (e.g.
wrístband)
Illustration of measurements
Right-headed vs. left-headed compounds in Boston Corpus
0.052
10
-5
0
5
3.332
-10
pitch difference in semitones
15
20
mean pitch difference in
semitones
rightleftheaded
headed
right-headed
wrístband
left-headed
attorney géneral
t (4408) = 4.91, p < 0.01, Cohen‘s d = 0.80
Boston Corpus: Structural hypothesis
Argument-head vs. modifier-head compounds
3.250
10
0
5
3.736
-5
significant difference, but
large overlap between the
two groups
-10
pitch difference in semitones
15
20
mean pitch difference in
semitones
argumentmodifierhead
head
argument-head
modifier-head
t (4089) = 2.36, p < 0.05, Cohen’s d = 0.01
effect size is very small
Boston Corpus: Structural hypothesis
A closer look at argument-head vs. modifier-head compounds
morphology
of head
argument-head
modifier-head
-er
law makers
house speaker
-ing
fundraising
spring training
-ion
jury selection
health education
conversion
tax increase
litmus test
(also, with low frequency: -age, -al, -ance, …)
Boston Corpus: Structural hypothesis
Interaction of structure and morphology of head
ing (N=81)
ion (N=198)
not significant
15
10
pitch difference in semitones
5
0
-5
-10
con (N=572)
er (N=349)
15
10
5
0
-5
F (9, 4062) = 2.89
p < 0.01
R² = 0.015
-10
Argument-Head
Modifier-Head
Argument-Head
Modifier-Head
Boston Corpus: Lexicalization effect?
Two ways of quantifying lexicalizationonly very small tendency
for highly frequent
compounds to be more
left-stressed
- Frequency
Higher frequency should correlate with higher degree of
lexicalization
no difference between
AH or MH compounds
F (1, 4069) < 1
- Spelling
Lexicalized compounds are more prone to one-word spellings
Boston Corpus: Lexicalization effect?
Pitch difference by Google frequency
10
3
0
2
5
• typical of categorical
nochanges
difference between
AH or MH compounds
1
-5
F (1, 4069) < 1
0
-10
pitch difference in semitones
pitch difference in semitones
4
15
5
only
very small
tendency
• relation
between
pitch
fordifference
highly frequent
and Google
compounds
be more
frequency to
shows
an Sleft-stressed
shaped distribution
0
0
5
5
10
15
10
15
log frequency (Google)
log frequency (Google)
F (1, 4071) = 15.58, p < 0.001, R² = 0.004
20
20
Boston Corpus: Lexicalization effect?
Spelling and lexicalization
Results:
• expected effect
• large effect size
=> spelling is an indicator of
lexicalization
15
10
5
Prediction:
compounds spelled as one
word should have higher
frequency than those spelled
as two words
log frequency (Google)
Assumptions:
• one-word spellings are
indicative of lexicalization
• high frequency is indicative
of lexicalization
20
Frequency by spelling
modifier-head compounds
one word
two words
spelling
t (3388) = 15.58, p < 0.001, Cohen´s d = 0.89
Boston Corpus: Lexicalization effect?
Interaction between structure and spelling
4.0
4.5
Argument-Head
Modifier-Head
• Modifier-Head compounds
spelled as one word should be
more left-stressed than
Modifier-head compounds
spelled as two words
• no effect of that kind with
Argument-Head compounds
3.5
Results:
3.0
pitch difference in semitones
5.0
Predictions:
one word
two word
spelling
F (3, 4030) = 12.79, p < 0.001, R² = 0.009
• Modifier-Head compounds
spelled as one word are indeed
more left-stressed
• spelling of Argument-Head
compounds does not interact
with stress position
• only very weak effect
Boston Corpus: Structural hypothesis
A summary
• significant effect of argument vs. modifier only with a subset of
potential compounds (i.e. –er as righthand head morphemes)
• a measurable lexicalization effect (based on frequency and
spelling)
• effect sizes are all very small – a lot of the variation is
unaccounted for under this hypothesis
The structural hypothesis is not well supported by the data
Boston Corpus: Semantic hypothesis
Methodological problems
• Semantic categories and semantic relations mentioned in the
literature (such as ‚N2 is a material‘, ‘N2 is located at N1’) are
hard to test due to their being generally ill-defined
• Items are often ambiguous (i.e. show more than one relation)
• The number of potentially relevant semantic categories and
relations is unclear
Our methodology
• We used a set of 18 semantic relations (based mainly on Levi
1978), also widely used in studies on compound interpretation
(e.g. Gagné & Shoben 1997, Gagné 2001)
• Semantic classification was done by two independent raters –
only those data are analyzed where the two ratings agreed
Boston Corpus: Semantic hypothesis
The literature on rightward stress makes use of either
categories referring to constituents or the
compound as a whole
or
categories referring to semantic relation
Boston Corpus: Semantic hypothesis
Categories referring to constituents or the compound as a whole
Rightward stress is predicted if...
•
•
•
•
N1
N2
N2
N1
refers to a period or point in time (morning edition)
is a geographical term (Boston area)
is a type of thoroughfare (Sesame Street)
and N2 form a proper noun (Tufts University)
(e.g. Fudge 1984: 144ff, Liberman & Sproat 1992)
Boston Corpus: Semantic hypothesis
Categories referring to constituents or the compound as a whole
N1 refers to POINT OF TIME?
yes
no
15
10
5
0
-5
-15 -10
-15 -10
-5
0
5
10
pitch difference in semitones
15
20
20
N1 is a PROPER NOUN?
yes
F (7, 4130) = 9.19, p < 0.01, R² = 0.0136
no
yes
-5
0
5
10
15
20
no
-15 -10
pitch difference in semitones
15
10
5
0
-5
yes
Compound is a PROPER NOUN?
pitch difference in semitones
N2 is a THOROUGHFARE?
20
no
-15 -10
pitch difference in semitones
15
10
5
0
-5
-15 -10
pitch difference in semitones
20
N2 is a GEOGRAPHICAL TERM?
no
yes
Boston Corpus: Semantic hypothesis
Categories referring to semantic relation
Rightward stress is predicted if...
•
•
•
•
N2
N2
N2
N1
DURING N1 (summer vacations)
IS LOCATED AT N1 (Newton residents)
IS MADE OF N1 (canvas bags)
MAKES N2 (Weld plan)
(e.g. Fudge 1984: 144ff, Liberman & Sproat 1992)
additional categories (18 in total):
• N1 HAS N2 (wheel chair)
• N2 USES N1 (breath test)
• N2 FOR N1 (adult prisons)
• N2 CAUSES N1 (AIDS virus)
•…
-5
0
5
10
15
no
yes
0
5
10
15
no
yes
F (7, 2036) = 20.53, p < 0.01, R² = 0.063
0
5
10
15
20
N1 HAS N2
-5
no
-10
20
yes
pitch difference in semitones
-5
20
no
-10
pitch difference in semitones
-10
-5
0
5
10
15
-5
0
5
10
15
yes
N2 USES N1
-5
0
5
10
15
no
no
yes
N2 FOR N1
yes
-10
-5
0
5
10
15
pitch difference in semitones
-10
pitch difference in semitones
-10
pitch difference in semitones
-10
20
20
20
20
N2 LOCATED AT/IN N1
-15
-15
-15
-15
pitch difference in semitones
N2 DURING N1
-15
-15
-15
pitch difference in semitones
Boston Corpus: Semantic hypothesis
Categories referring to semantic relation
N1 MAKES N2
N2 IS MADE OF N1
no
yes
Boston Corpus: Semantic hypothesis
A summary
• Some predictions are correct
• Some predictions are wrong (i.e. no effect found)
• Some effects are found where no prediction is made
• A lot of the variation is unaccounted for under this hypothesis
The semantic hypothesis is not well supported by the data
Boston Corpus: Analogical hypothesis
Analogical modeling is not yet possible at the moment,
due to gradient stress measurements
(But see Kunter/Plag (2006) on how this can be done)
CELEX: General overview
Contents
stress position
left
right
Oxford Advanced Learner's Dictionary
(1974): 41,000 lemmata
Longman Dict. of Contemp. Engl.
(1978): 53,000 lemmata
COBUILD corpus (92%)
17.9 million word tokens
90%
overall: 52,446 lemmata
representing 160,594 wordforms
Position of stress is given for
each entry in the data base
NNN compounds = 4491
10%
CELEX: Structural hypothesis
Argument-head vs. modifier-head compounds
significant difference is in
the direction predicted by
the hypothesis (i.e. more
left stress with argumenthead compounds)
left
right
stress position
but:
vast majority of modifierhead compounds is also
left-stressed, which goes
against the hypothesis
modifier-head
χ ² = 8.55, df = 1, p < 0.01, φ = 0.05
argument-head
CELEX: Structural hypothesis
Interaction of structure and morphology of head
argument-head
left
• same significant interaction
as in BURSC
• other interactions are not
significant
con
morphology
• significant effect of
argument vs. modifier only
with a subset of potential
compounds (i.e. –er as
righthand head morphemes)
right
er
ing
ion
logit regression, null dev. = 396.64, df = 680;
residual dev. = 354.23, df = 673
structure
modifier-head
left
right
CELEX: Lexicalization effect?
Frequency and stress position
15
10
5
Results:
• Google log frequencies are not
different for left- or right-stressed
compounds
• no interaction of stress position and
structure (F (1, 4467) = 2.47, p = 0.12)
Æ stress position is not related to
frequency
log Google frequency
Prediction:
left-stressed compounds should
have higher frequency than rightstressed compounds
20
Assumptions:
• lexicalized compounds prefer leftstress
• lexicalized compounds are more
frequent
left
right
t (4470) = 1.097, p = 0.27
CELEX: Lexicalization effect?
Spelling and stress position
• the more lexicalized (in
terms of spelling), the
more frequent is left
stress
• no difference between
argument-head and
modifier-head
compounds
⇒ evidence for general
lexicalization effect on
stress
stress position
one word
hyphenated
left
right
spelling
χ ² = 512.08, df = 2, p < 0.01
two words
CELEX: Structural hypothesis
A summary
• significant effect of argument vs. modifier only with a subset of
potential compounds (i.e. –er as right-hand head morpheme)
• BUT: the vast majority of compounds do not behave in accordance
to the hypothesis
• measurable general lexicalization effect (only w.r.t. spelling)
The structural hypothesis is not supported by the data
CELEX: Semantic hypothesis
right
right
right
N2 is a GEOGRAPHICAL TERM?
no
N2 is a THOROUGHFARE?
left
left
right
right
Compound is a PROPER NOUN?
logit regression, null dev. = 2784.0, df = 4125; residual dev. = 2693.1, df = 4120
yes
no
yes
left
yes
no
N1 refers to POINT OF TIME?
left
N1 is a PROPER NOUN?
yes
left
no
yes
no
Categories referring to constituents or the compound as a whole
CELEX: Semantic hypothesis
left
left
left
right
right
right
left
left
left
right
right
right
N1 IS N2
N2 FOR N1
logit regression, null dev. = 1149.16, df = 1629; residual dev. = 967.41, df = 1614
N2 ÍS NAMED AFTER N1
yes
no
N2 IS MADE OF N1
yes
no
N2 LOCATED AT/IN N1
yes
no
N2 DURING N1
yes
no
yes
no
yes
no
Categories referring to semantic relation
CELEX: Semantic hypothesis
Summary
• Some predictions go in the right direction, but leave lots of data
unexplained
• Some predictions are wrong (i.e. no effect found)
• Some effects are found where no prediction is made
• A lot of the variation is unaccounted for
The semantic hypothesis is not well supported by the data
CELEX: Analogical hypothesis
Specific hypothesis:
Stress in compounds is determined by the stress pattern of the
majority of similar instances that are stored in memory.
Example:
cárpet beater is assigned left stress because the most similar
exemplar stored in memory, éggbeater, also has left stress.
CELEX: Analogical hypothesis
The data
Compounds whose left and right members occur more than once
in the corpus, i.e. for which the model has information about
constituent families of the members.
N = 2643
(Ntotal = 4491)
The model
Memory-based learner (TiMBL 5.1, Daelemans et al. 2004)
How does TiMBL work?
INSTANCE-BASED
MEMORY
SET OF
NEAREST NEIGHBOURS
oil painting
oil, painting, noarg,-ing, semcat1
INPUT
action,
finger,
wall,
country,
cottage,
painting,
painting,
painting,
party,
hospital,
noarg,
noarg,
arg,
noarg,
noarg,
-ing,
-ing,
-ing,
nosuff,
nosuff,
semcat1, stress: left
semcat1, stress: left
semcat1, stress: left
semcat2, stress: left
semcat3, stress: right
life,
...
work,
noarg, nosuff,
semcat2, stress: right
action,
finger,
painting, noarg, -ing,
painting, noarg, -ing,
semcat1, stress: left
semcat1, stress: left
evaluation of
input against nearest neighbours
}
stress left: 2x
stress right: 0x
oíl painting
stress left
OUTPUT
How does TiMBL perform?
- 94 % overall accuracy
- predictive accuracy for right stresses: 20-25%
Which features does TiMBL find useful?
Any given set of features does the same thing as any other set of
features (about 94 % accuracy):
semantic categories, semantic relations, proper-noun status,
morphological structure, argument-head status,
left and/or right member
⇒ No abstract features needed, left and right member can do the job
Left and right member are in fact better predictors than the other
features, because
only when we leave out left and/or right member do we find a
significant drop in performance
(left member: Yate’s χ2 = 7.42, p < 0.01, right member: Yate’s χ2 = 4.83, p < 0.05, left and right
member: Yate’s χ2 = 4.83, p < 0.05)
The results of analogical modeling
Accuracy
• pretty good overall predictive accuracy
• better predictive accuracy than under any other hypothesis
Predictors
none of the grammatical/semantic features proposed in the
literature improves predictive accuracy
Theoretical implication
constituent families (and thus analogy) play an important role in
compound stress assignment
Summary and Conclusion
• Corpus data do not confirm the categorical stress assignment
rules found in the literature
• Compound stress is much more variable than previously thought
• Argument structure effects are restricted to compounds ending
in –er
• There are only small effects of only some of the semantic
categories proposed in the literature
• Assignment of rightward stress is problematic for TiMBL. But
TiMBL is better than any other “rule“ found in the literature
• Analogical effects based on constituent families play an
important role in compound stress assignment
Thank you very much for your attention!
Acknowledgements
- Christian Grau, Christina Kellenter, and Taivi Rüüberg for their help with annotating
the data
- Harald Baayen and Mark Pluymaekers for statistical training and support, and for
critical comments and suggestions
- Heinz Giegerich for critical comments and support
- Deutsche Forschungsgemeinschaft for funding this research (Grant PL151/5-1)
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