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Language, Cognition and Neuroscience
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Grammatical and information-structural influences on
pronoun production
H. Rohdea & A. Kehlerb
a Department of Linguistics and English Language, University of Edinburgh, Edinburgh, UK
b Department of Linguistics, University of California San Diego, La Jolla, CA, USA
Published online: 12 Nov 2013.
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To cite this article: H. Rohde & A. Kehler (2014) Grammatical and information-structural influences on pronoun production,
Language, Cognition and Neuroscience, 29:8, 912-927, DOI: 10.1080/01690965.2013.854918
To link to this article: http://dx.doi.org/10.1080/01690965.2013.854918
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Language,Cognition andNeuroscience, 2014
Vol.29,No.8, 912–927,http://dx.doi.org/10.1080/01690965.2013.854918
Grammatical and information-structural influences on pronoun production
H. Rohdea* and A. Kehlerb
aDepartmentofLinguisticsandEnglishLanguage,UniversityofEdinburgh,Edinburgh,UK;bDepartmentofLinguistics,Universityof
California SanDiego, La Jolla,CA,USA
(Received 1 March2012;accepted3 October 2013)
A standard assumption in psycholinguistic research on pronoun interpretation is that production and interpretation are
guidedbythesame setofcontextualfactors.Alineofrecent researchhas suggestedotherwise, however,arguinginstead
thatpronounproductionisinsensitivetoaclassofsemanticallydrivencontextualbiasesthathavebeenshowntoinfluence
pronoun interpretation. The work reported in this paper addresses three fundamental questions that have been left
unresolved by this research. First, research demonstrating the insensitivity of production to semantic biases has relied on
referentially unambiguous settings in which the comprehender’s ability to resolve the pronoun is not actually at stake.
5 Experiment 1, a story continuation study, demonstrates that pronoun production is also insensitive to semantic biases in
1 settings in which a pronoun would be referentially ambiguous. Second, previous research has not distinguished between
0
2 accountsinwhichproductionbiasesaredrivenbygrammaticalpropertiesofintendedreferents(e.g.,subjectposition)orby
ry information-structuralfactors(specifically,topichood)thatareinherentlypragmaticinnature.Experiment2examinesthis
a
u questionwithastorycontinuationstudythatmanipulatesthelikelihoodofpotentialreferentsbeingthetopicwhilekeeping
n
a grammatical role constant. A significant effect of the manipulation on rate of pronominalisation supports the claim that
J
6 pronoun production is influenced by the likelihood that the referent is the current topic. Lastly, the predictions of Kehler
2
6 et al.’s Bayesian analysis of the relationship between production and interpretation have never been quantitatively
0 examined. Theresults ofboth experiments areshown tosupport the analysis overtwocompeting models.
6:
1
at Keywords: pronounproduction; implicit causality;information structure
]
y
ersit Like all natural languages, English offers its speakers1 a be prominent in the comprehender’s mental model of the
v
ni wide variety of referring expressions from which to discourse at the time of utterance, and correspondingly,
U
nell cnhoouonsse). (Te.hgi.s, porbospeervrantiaomnesim, mdeefdiniaitteelydegsicvriepstiorinsse, tporoa- cTohmepreremhaeinndinegrstianstkerfporreptspyrcohnooluinngsutoistriecferersteoarscuhchisemnteitrieelsy.
k
c question: What factors will guide a speaker in determin- to identify those factors (grammatical, semantic, informa-
u
B ing which of these alternatives to select in a particular tion-structural and so forth) that determine the degree of
[
by context so as to communicate successfully? As is well prominence of potential referents.
ed known,thechoiceisfarfromarbitrary,beingconstrained Numerous authors have weighed in on this question,
d
a by such factors as assumed knowledge of the referent by positing a range of biases that involve both structurally
o
nl the addressee, prior evocation in the discourse, and level driven and semantically driven factors. In this paper, we
w
o of activation in the addressee’s mental state, among examine thepredictionsofa Bayesianmodel proposedby
D
others. Kehler, Kertz, Rohde, and Elman (2008) that specifies a
Undoubtedly,themostwell-studiedreferentialformin more complex relationship between production and inter-
psycholinguistics is the singular, third-person personal
pretation.Accordingtothismodel,structuralandsemantic
pronoun.Therecurringclaimwhichoneencountersinthe
factors play fundamentally different roles: Whereas pro-
literature is that pronoun use requires a high degree of
noun production biases are determined primarily by
activation of the referent in the cognitive state of the
structural factors, the interpretation process integrates
comprehender, a concept variously referred to as being
these biases with semantically driven expectations about
PROMINENT, SALIENT, ACCESSIBLE, IN FOCUS, or THE what entity will be mentioned next—henceforth referred
CENTRE OF ATTENTION, among other characterisations to as next-mention biases—that hold independently of the
(Ariel, 1990; Arnold, 2001, 2010; Grosz, Joshi, &
form of reference ultimately chosen by the speaker. A
Weinstein, 1995; Gundel, Hedberg, & Zacharski, 1993;
consequence of the model is that pronoun production and
inter alia). The picture that results is that production and
interpretation processes are in fact not mirror images of
interpretation are mirror images of each other: Speakers
each other, since pronoun interpretation utilises a set of
produce pronouns to denote referents that they believe to
*Corresponding author.Email: [email protected]
©2013Taylor&Francis
Language, Cognition and Neuroscience 913
contextual factors that production processes ignore—an argued for a first-mention advantage, whereby it is the
intuitively strange set of affairs. first-mentioned entity that has a privileged status for
We report on two experiments that provide evidence subsequent reference (see also Järvikivi, van Gompel,
for the model by way of addressing three fundamental Hyönä, & Bertram, 2005). Other researchers, including
questions that have as yet been left unanswered. First, Smyth (1994) and Chambers and Smyth (1998), have
previous experiments that have offered preliminary sup- argued instead for a parallel grammatical role preference,
port for the insensitivity of pronoun production to whereby the preferred referent for a pronoun will be
semantically driven next-mention biases have employed the entity that occupies the same grammatical role in
unambiguous contexts. This is potentially problematic the previous clause. In this account, the prominence of
since it stands to reason that such biases could be safely the parallel entity falls out naturally from a structurally
ignored by a speaker when a pronoun would not be governed Extended Feature Match process. Yet other
ambiguous to begin with. Experiment 1, a story continua- researchers have argued for the role of semantic and
tion study, examines production biases in a referentially world knowledge as the central factor that determines
ambiguous setting, and shows that the insensitivity of the preferred referent. According to Hobbs (1979), for
production to next-mention biases extends to ambiguous example, pronouns are represented merely as free vari-
situations. Second, previous work has not pinpointed the ables that get bound to referents as a side-effect of
underlying source of the biases on the production side: discourse-level inference processes. Finally, some research-
5
1 specifically, whether they are grammatically driven (e.g., ers have posited that prominence is determined by a
0
y 2 bysubjecthood),asmuchoftheliteraturehasassumed,or combination of many factors, with none being singled out
ar following the claims of early incarnations of Centering as primary. According to Arnold’s (2001) Expectancy
u
n Theory (Grosz et al., 1995) as well as linguistic accounts Hypothesis, for instance, prominence is inherently prob-
a
J
6 (Ariel, 1990; Gundel et al., 1993; Lambrecht, 1994), are abilistic, correlated directly with the likelihood that a
2
6 driven instead by information-structural biases (specific- particular entity will be mentioned next. Numerous factors
0
6: ally, topichood) that are inherently pragmatic in nature. determine likelihood of next mention: the aforementioned
at 1 Experiment 2 examines this question with a story subjecthood, grammatical parallelism and semantic influ-
] continuation study that manipulates the likelihood of ences being among them. Despite their differences, these
y
sit potential referents being the topic while keeping gram- accounts all share the implicit assumption that the same
r
e maticalroleconstant.Instarkcontrasttothelackofeffect contextual properties that license the speaker to use a
v
ni of semantically driven next-mention biases, the results pronoun are those that the comprehender will rely on to
U
ell demonstrate that topicality influences pronoun production interpret it.
n beyond what can be accounted for by grammatical role. However, another line of work has painted a more
k
c Third, the predictions about interpretation biases made by complex picture: one which suggests that pronoun pro-
u
B
the Bayesian analysis have not been quantitatively tested ductionandcomprehensionarenotdrivenbythesameset
[
by to date. The results of Experiments 1 and 2 are both of contextual factors (Fukumura & van Gompel, 2010;
ed shown to support the predictions of the account. Kehler et al., 2008; Miltsakaki, 2007; Rohde, 2008;
d
a Stevenson, Crawley, & Kleinman, 1994). Stevenson et al.
o
nl (1994) reported on a series of story continuation experi-
w
o Background: interpretation biases ments that investigated pronoun biases across eight
D
Previous literature has posited a variety of factors that distinct context types. Particularly revealing were the
influence how comprehenders will assign referents to results for two contexts that employed transfer-of-posses-
pronouns.Forinstance,Crawleyetal.(1990)haveargued sion verbs as in the following:
that comprehenders use a subject-assignment strategy,
(1) Transfer-of-possession contexts from Stevenson
whereby the entity mentioned from the subject position
et al. (pronoun condition)
of the previous clause is, all else being equal, considered
a. John seized the comic from Bill. He___________
more prominent than referents occupying other grammat-
b. Johnpassed thecomicto Bill. He_____________
icalroles.TheCentering-basedinterpretationalgorithm of
Brennan, Friedman, and Pollard (1987) and Walker, Iida, Both contexts describe events with Source and Goal
and Cote (1994) also ranks subjects as higher than other referents; in (1a) the Goal occupies the subject position,
referents on a prominence hierarchy (specifically, the whereas in (1b) it appears as the object of a prepositional
forward-lookingcenterlist),althoughthehierarchyaffects phrase (PP). Stevenson et al. found that Goal–Source
pronoun interpretation only indirectly, through a ranking prompts like (1a) yielded significantly more continuations
of discourse transition types that arise from different in which the ambiguous pronoun He is used to refer back
referent assignments.2 On the other hand, researchers to the subject than the non-subject (85%). Following a
such as Gernsbacher and Hargreaves (1988) and Source–Goal prompt like (1b), on the other hand,
Gernsbacher, Hargreaves, and Beeman (1989) have participantswereequallylikelytoreferbacktothesubject
914 H. Rohde and A. Kehler
and Background: production biases
non-subject (51% bias to the subject). The fact that an
The foregoing data explains how semantic biases towards
object-of-PPreferentattheendofthesentence–normally entity next-mention can conspire with a subject bias
a relatively non-prominent position for pronominal refer-
associated with pronouns to produce the ultimate inter-
ence – competes with the sentential subject is somewhat pretation bias in ambiguous contexts. There is one result
surprising, especially in light of the previously discussed
of Stevenson et al.’s that remains unexplained by this
firstmention,subject-assignmentandparallelgrammatical
picture,however.Recallthatintheirno-pronouncondition
role biases, all of which favour the subject. Stevenson
(2), participants not only chose who to refer to first, but
etal.concludedthattherearetwotypesofbiasatworkin
also the form of reference to use. Across their stimulus
suchexamples:athematicrolebias(here,favouringGoals
types, they found that this choice was heavily biased
over Sources), and a grammatical role bias (favouring
towards a pronoun when the referent was the previous
subjects over other roles). The Goal bias and the subject
subject, and likewise towards a name when the referent
bias agree on the same referent in the Goal–Source was a non-subject. (Arnold, 2001 also found correspond-
condition, predicting the large percentage of Goal inter-
ingly strong biases in a similar experiment.) This result
pretations. The two biases compete in the Source–Goal mayatfirstseemcontradictory:Ifparticipantshaveaclear
condition, on the other hand, predicting an even distribu-
preferencetousepronounstorefertotheprevioussubject
tion of assignments.
5 and names to refer to non-subjects, why would the
1 Importantly,Stevensonetal.concludedthatthewayin
0 interpretation bias for the pronouns in passages like
y 2 which these two biases come to affect pronoun interpreta- (1) be 50–50? Hence we have evidence for a dissociation
uar tion are fundamentally different: The thematic role bias between production and interpretation.
n emerges via a “top-down” predictive mechanism that
a Kehler et al. (2008) offered an explanation for the
J
6 determines the prominence of an entity even before a apparent contradiction by modeling the relationship
2
6 referring expression is encountered (and hence applies between production and interpretation in terms of Bayes’
0
6: regardless of the form of referring expression chosen by Rule, as shown in (3).
at 1 thespeaker),whereasthesubjectbiasresultsfromaform-
] specific, “bottom-up” response to the presence of a (3)
y
sit pronoun. Evidence for the top-down nature of thematic P referent pronoun
ver role biases came from the fact that, in addition to the ð j P pÞronoun referent P referent
ni pronoun-prompt conditions in (1a) and (1b), they also ð j Þ ð Þ
U ¼ P pronoun referent P referent
ell tested versions that did not include the pronoun as in the referent2referents ð j Þ ð Þ
n following: P
k
Buc (2) Transfer-of-possession contexts from Stevenson Tbihaes:tethrmepPro(rbeafbeirleintyt,∣pgriovneonutnh)atreapprerosennotusnthheasinotcecrpurreretadt,ioonf
by [ et al. (no-pronoun condition) it being used by the speaker to refer to a particular
ed a. John seized the comic from Bill.______________ referent. On the other hand, the term P(pronoun∣referent)
d b. JohnpassedthecomictoBill.________________
a represents the production bias: the probability, assuming
o
nl Here, participants not only choose who to refer to first thataparticularentityisbeingreferredto,thatthespeaker
w
o inthecontinuation butalsotheformofreferencetouse; wouldhaveusedapronoun torefer toit. Bayes’rulesays
D
the distribution of first mentions therefore provides that these biases are not mirror images of each other, but
estimatesofthenext-mentionbiasesthatcomprehenders instead are related by the prior P(referent), which
have after reading the context sentence. Stevenson et al. represents the next-mention bias: the probability that a
found a Goal bias in this condition that paralleled the particular referent will get mentioned next regardless of
one found in the pronoun condition, supporting the the referring expression used.3 Equation (3) thus explains
idea that the effect is independent of whether a pronoun why there is nothing contradictory about having both a
is used. Evidence for the form-specific, “bottom-up” strong production bias towards pronominalising the pre-
nature of the subject bias, on the other hand, came from vious subject (and not pronominalising non-subjects) and
the fact that there was a greater percentage of first yetalackofasubjectbiasininterpretation,aslongasthe
mentions of the previous subject in the pronoun condi- prior P(referent) points strongly enough away from the
tions than in the corresponding no-pronoun conditions. subject referent. The roughly 50–50 distribution of
Taken together, these two results support the idea that references to the Source and Goal in transfer-of-posses-
the occurrence of a pronoun contributes a subject bias sion passages like (1b) results from the fact that for the
that operates independently of, albeit in concert with, subject referent, the next-mention bias is low and the
contextually driven, top-down next-mention biases in pronominalisation bias is high, whereas for the non-
determining the ultimate interpretation bias for the subject referent, the next-mention bias is high and the
pronoun. pronominalisation bias is low.4
Language, Cognition and Neuroscience 915
On Kehler et al.’s analysis, therefore, the bottom-up aspect manipulation had no effect on rate of pronomina-
interpretation bias towards subjects that Stevenson et al. lisation; only grammatical role mattered.5
posited for pronouns is actually the result of a production Other experiments have employed contexts with so-
bias towards pronominalising references to the subject. A called implicit causality (IC) verbs. Such verbs (e.g.,
comprehender’s interpretation bias thus relies jointly on impress, admire, detest, annoy, congratulate) are well
his estimates of the likelihood that a particular referent known to create a bias to re-mention the causally
will be mentioned next (regardless of form of reference) implicated referent, especially in an upcoming clause
andofthelikelihoodthatthespeakerwouldhavechosena that provides a cause or reason (Au, 1986; Brown &
pronoun (instead of another form of reference) to refer to Fish, 1983; Caramazza, Grober, Garvey, & Yates, 1977;
that referent. The predictions of the analysis can be tested Garvey&Caramazza,1974;Kehleretal.,2008;McKoon,
using story continuation experiments: the values for the Greene, & Ratcliff, 1993, inter alia). Some IC verbs are
terms on the right-hand side of Equation (3) can be subject-biased, such as impress in (4a), because the
estimated from the data collected in no-pronoun-prompt causally implicated referent occurs in subject position.
conditions (2), which will yield a prediction for Other verbs are object-biased, such as admire in (4b),
because the causally implicated referent occurs in object
P(referent∣pronoun). If the Bayesian characterisation is
position:
correct, this predicted bias should be highly correlated
5 with the actual interpretation biases estimated directly in (4) IC contexts with opposite-gender referents
1
0 pronoun-prompt conditions (1) in otherwise identical a. John impressed Mary.______________________
2
y contexts. b. John admired Mary.________________________
r
ua At this point, an intriguing picture has emerged; one
n The strong divergence between the next-mention biases
a which suggests that the contributors to the ultimate
J
6 interpretation bias are conditioned by different sets of for subject-biased and object-biased IC verbs makes the
2
6 contextual factors. On the one hand, the data suggest that alternation particularly useful for examining whether
0
6: thefactorsthatconditionthenext-mentionbiasP(referent) rate of pronominalisation is affected by semantic
1
at are primarily semantic. On the other hand, the factors that factors. Rohde (2008, Experiment V) elicited story con-
] tinuations with contexts such as (4a) and (4b), as well
y condition the production bias P(pronoun∣referent) appear
rsit to be structural (e.g., based on grammatical role). Con- as with non-IC context controls (John chatted with
e Mary._____________). Whereas grammatical role again
v sideringthisinlightoftheasymmetrybetweenproduction
ni influenced rate of pronominalisation, there was no inter-
U and interpretation captured by Equation (3), this picture
ell makes a striking prediction: that the speaker’s decision action between grammatical role and verb type, showing
n that the rate of pronominalisation does not depend on the
k about whether or not to pronominalise a reference will be
uc next-mention bias of the verb. Two experiments reported
B insensitive to the semantically driven contextual factors
[ by Fukumura and van Gompel (2010) yielded highly
y that in part determine the comprehender’s interpretation
b complementary results. Their first experiment used con-
ed biases.Thishypothesisissurprisingbecauseitviolatesthe texts that varied IC bias with because prompts (Gary
d intuition that speakers will pronominalise mentions of
a scared/feared Anna after the long discussion ended in a
o
nl referents in just those cases in which their comprehenders row. This was because___________). Their second
w
wouldbeexpectedtointerpretthepronounstothosesame
o experiment used only subject-biased IC verbs but varied
D
referents.
the connective between because and so; these verbs are
Theresultsofseveralrecentstorycontinuationstudies
known to flip from a subject bias with because to an
have provided preliminary support for this prediction. For
object bias when so is used (Stevenson et al., 1994). In
instance, Rohde (2008, Experiment VII) reports on a both cases, the manipulation affected the choice of who
continuation study that employed an aspect manipulation got mentioned next but not the rate of pronominalisation.
(perfective vs. imperfective) using transfer-of-possession Once again, the only factor that affected pronominalisa-
contextswithno-pronounprompts(e.g.,Suehanded/was tion rate was the grammatical role of the referent.
handing a timecard to Fred.__________). (The motiva- A legitimate complaint that could be lodged against
tion for this design was a previous experiment that these studies, however, is that the contexts mention two
demonstrated that this aspect manipulation significantly opposite-gendered individuals, meaning that the sub-
influences interpretation biases, with a greater number of sequent pronoun is never ambiguous. As such, they do
references to the Goal in the perfective case than in the notdemonstratethat interpretation biasesdo not influence
imperfective case (Rohde, Kehler, & Elman, 2006).) As the rate of pronominalisation when an ambiguity is
expected,themanipulationinfluencednext-mentionbiases present; it is quite possible that speakers would only
in the predicted direction, both for the set of all continua- attend to interpretation biases in contexts in which the
tions as well as for the subset of continuations in which comprehender’s ability to resolve the pronoun to the
the participant chose to use a pronoun. However, the correct referent is actually in question. To address this,
916 H. Rohde and A. Kehler
our first experiment examines production biases in IC (5a)-(5c).Assuch,ourhypothesispredictsamaineffectof
contextsinwhichreferenceisambiguous.Establishingthe referent position (subject vs. non-subject) on rate of
lack of effect of semantic bias in such contexts not only pronoun production, but the effect of referent position is
provides an important test of the analysis, but it is also a notexpectedtovarywithverbbias(noreferentposition×
necessaryprerequisitetoourExperiment2,whichwilluse verb bias interaction). On the other hand, an interaction
gender-ambiguous contexts to examine whether produc- with verb bias would suggest that speakers are in fact
tion biases are driven primarily by grammatical or accounting for interpretation biases in their decisions to
information-structural factors. pronominalise, presumably favouring pronominalisations
of the referent favoured by the IC bias of the verb.
Experiment 1
To address the question of whether production biases are
Methods
immune to semantic biases in situations in which refer-
Participants
ence is ambiguous, we conducted a story continuation
study using contexts that contain competing referents of Twenty-eight monolingual English-speaking undergradu-
the same gender.6 The story continuation prompts in (5) ates from UC San Diego participated in the experiment
implement a 3×2 design, utilising three types of context either for extra credit in Linguistics courses or for the
15 (containing subject-biased IC verbs, object-biased IC chance to be entered in a raffle to win a gift certificate.
0
2 verbs and non-IC verbs), as well as the now-familiar
y
ar prompt manipulation in which a sentence-initial pronoun Materials and procedure
u
n for the continuation either is or is not included.
a For the experimental items, each context sentence men-
J
6 (5) Manipulation of verb bias and continuation tioned two referents in a situation described with a
2
6 prompt in gender-ambiguous contexts subject-biased IC verb, an object-biased IC verb, or a
0
6: a. John infuriated Bill. ________________ non-IC verb, as in (5). The two competing referents were
1
at [Subject-biased IC verb, no-pronoun] of the same gender, counterbalanced between male and
y] b. John scolded Bill. __________________ female names. Eighty verbs were taken from Kehler et al.
sit [Object-biased IC verb, no-pronoun] (2008), who in turn adapted them from McKoon et al.
r
e
v c. John chatted with Bill._____________________ (1993) consisting of 40 IC verbs (20 subject-biased,
ni
U [Non-IC verb, no-pronoun] 20 object-biased) and 40 non-IC verbs. The experiment
ell d. John infuriated Bill. He _______________ consisted of 100 items: 80 experimental items (40 IC,
n
k [Subject-biased IC verb, pronoun] 40 non-IC) intermixed with 20 non-IC fillers. The addi-
c
Bu e. John scolded Bill. He ________________ tional fillers consisted of prompts with context sentences
y [ [Object-biased IC verb, pronoun] containing non-IC verbs followed by intersentential con-
b
d f. John chatted with Bill. He ______________ nectives, no-pronoun or pronoun prompts.
e
d [Non-IC verb, pronoun] Story continuations were collected via a web-based
a
o
nl Crucial to the design is the expectation that previous interface that participants could access from their own
w computer. Each item was presented on a page by itself
o results for IC-driven next-mention and interpretation
D with a text box in which participants were instructed to
biases will be replicated. That is, we expect to find more
write their continuation. The entire experiment took
first mentions of the subject following subject-biased IC
roughly 45 minutes, but participants were encouraged to
contexts than object-biased IC contexts in both the no-
have an hour available so that the experiment could be
pronoun (next-mention bias) and pronoun (interpretation
bias) conditions. (We have no predictions about the more completed in one session. Participants could leave the
heterogeneous set of verbs used for the non-IC context website and return at a later time by identifying them-
condition, which was included as a control to ensure that selves with an ID number. They were instructed to
the production results are consistent across a broader set imagine a natural story continuation for each prompt,
of context types.) Finally, the production bias associated writing the first continuation that came to mind and
with pronouns predicts a greater number of first mentions avoiding humor.
of the subject in the pronoun-prompt condition than the In this task, participants create a mental model of the
corresponding no-pronoun condition for each context eventinthecontextsentenceandthenwriteacontinuation
type. that reflects their expectations about where the story is
Replicating these effects sets the stage for testing our going. As such, the task involves both interpretation and
hypothesis about production. Specifically, if production production (Arnold, 2001). The pronoun provided in the
biasesareunaffectedbynext-mentionbiases,thentherate pronoun-prompt condition constrains the surface realisa-
of pronominalisation is predicted to be the same across tion of their continuation, but their continuation depends
Language, Cognition and Neuroscience 917
1.0
ontheirexpectationsabouthowthediscoursewillproceed
No-pronoun prompt
andwhichindividualintheeventwillbementionedagain. ct 0.8 Pronoun prompt
e
bj
u
s 0.6
n
Evaluation and analysis o
rti 0.4
Two judges, the first author of this paper and a UC San o
p
Diego Linguistics undergraduate, coded the first-men- ro 0.2
P
tioned referent in each continuation (which, in the case
0.0
of the pronoun-prompt condition, was the assignment of Subj-biased IC Obj-biased IC Non-IC
thepronoun).Thejudgeswereinstructedtoerrontheside
Figure1. Proportionofcontinuationsaboutthesubject,byverb
of categorising a pronoun as ambiguous if the pronoun
bias andprompttype.
could be interpreted as plausibly co-referential with either
referent, even if their own interpretation biases suggested
a particular one. We first ask whether the context manipulation had the
To measure the effects of several predictors on the predicted effects on next-mention (no-pronoun condition)
observed choice of first mention and the observed choice and pronoun interpretation (pronoun condition) biases.
of referring expression, we used mixed-effect logistic Figure 1 shows the rate at which participants wrote
5
1 regressions(Jaeger,2008).Wemodelledthebinarychoice continuations about the subject across the six conditions.
0
y 2 of first mention (subject vs. non-subject) with fixed-effect As predicted, the results replicated the widely reported IC
ar predictors for verb bias, prompt type and the interaction bias—that the preferred entity for next mention following
u
n between the two. For the binary choice of referring an IC verb is the causally implicated one. To test for a
a
6 J expression (pronoun vs. not), we considered only the main effect of verb bias, we conducted a likelihood-ratio
6 2 continuations elicited in the no-pronoun condition and test between mixed-effects models differing only in the
6:0 modelled the observed referring expressions with predic- presence or absence of a fixed main effect of verb bias.
] at 1 tboertswefoenr rthefeertewnot.pBoostihtiopnr,omveprtbtybpieasanadndretfheereninttperoascittiioonn Bmoatihnmefofedcetlsoifncplruodmedptintytphee,irafnixdedanefifnetcetrsacatnioinntebrectewpet,ena
y
sit variedwithinparticipantsandwithinitems;verbbiasonly verb bias and prompt type. The likelihood-ratio test
er varied within participants. The referent position and showed a main effect of verb bias (p < 0.001, 1 d.f.).
v
ni prompttype predictorswerecentred.Forverbbias, which Pairwise comparisons showed that the binary predictor
U
nell ibseaathbrleee-tloevetelsptrefdoirctomr,aiwneeufsfeedctssumincothdeingprienseonrcdeerotof vneerxbtmbieanstioisnainstihgenisfuicbasnettsfcaoctnotrainfoinrgmoondlyelsinugbjecchto-biciaeseodf
k
c interactions. All models contained maximal random andobject-biasedICverbs(β=1.266,p<0.001)andonly
u
[B effects structure for both participants and items, namely object-biased IC verbs and non-IC verbs (β = 1.034,
by random intercepts plus random slopes for all predictors p < 0.001), but not for the subset containing subject-
ed and their interactions (Barr, Levy, Scheepers, & Tily, biased IC verbs and non-IC verbs (β = 0.248, p = 0.16).
d
a 2013). We report the coefficient estimate and p-value for Inkeepingwithpreviousresultsandthepredictionsof
o
nl each binary predictor (based on the Wald Z statistic; the Bayesian model, prompt type was a significant factor
w
o Agresti,2002).Forthesum-codedverbbiaspredictorand aswell(β=1.068,p<0.001),withpronounpromptsbeing
D
its interactions, we use likelihood-ratio tests to compare associated with higher rates of subject first mentions than
mixed-effects models differing only in the presence or no-pronoun prompts: 90.4% vs. 73.0% for subject-biased
absence of the fixed factor that pertains to verb bias. IC verbs; 61.6% vs. 26.4% for object-biased IC verbs;
86.1% vs. 54.3% for non-IC verbs. Again using model
comparison, a likelihood-ratio test showed no evidence for
Results and discussion a verb bias × prompt type interaction (p = 0.53, 1 d.f.).
The results reflect a conservative analysis in which a Wenowaskwhetherthedifferentsemanticbiasesthat
continuation was excluded if at least one judge assessed influence next mention and pronoun interpretation prefer-
the pronoun reference as ambiguous (15.7% of the total ences have an effect on pronoun production. The rates of
2240 continuations). Also excluded were cases in the no- pronominalisation in the no-pronoun condition are shown
pronounconditioninwhichbothreferentswerementioned in Figure 2. The analysis of referring expressions repli-
together in a plural pronoun or conjoined noun phrase cates the previously reported bias to pronominalise
(10.0%),neitherwasmentionedatall(2.1%),themention references to the subject. In a logistic regression, referent
used a referring expression other than a pronoun or name position was the only significant factor in modeling the
(1.9%), or the relationship between the continuation and binary outcome of pronominal referring expression (β =
the prompt was not clear (2.6%). This left a dataset of −2.14, p < 0.001), with more pronouns used for subject
1516 continuations. mentions than object mentions across all verb types:
918 H. Rohde and A. Kehler
Subject references pronouns as unbound variables (Hobbs, 1979). The
1.0 Non-subject references
predicted interpretation bias for this model is thus
s
n
u 0.8 estimated to be the next-mention bias P(referent) meas-
o
n ured in the no-pronoun condition. The second competing
o
r 0.6
p model is what we call the Mirror model, according to
n
o 0.4 which the interpretation bias towards a referent is propor-
orti tional to the likelihood that a speaker would produce a
p 0.2
o pronoun to refer to that referent. Capturing the intuition
r
P
0.0 that speakers will choose a pronoun in those cases in
Subj-biased IC Obj-biased IC Non-IC
which hearers will be biased towards the correct referent,
Figure 2. Rate of pronominalisation, by verb bias and referent thepredictedinterpretationbiasforthismodelisestimated
position(subject vs. non-subject). using the pronominalisation rate P(pronoun∣referent)
measured in the no-pronoun condition. Because these
values will not typically result in a valid probability
77.5% vs. 26.6% for subject-biased IC verbs; 80.8% vs.
distribution (i.e., the probabilities over referents will not
21.7% for object-biased IC verbs; 85.0% vs. 16.5%
sum to 1), the values are normalised with a scaling factor
for non-IC verbs. To test for a main effect of verb bias
(the sum of the pronominalisation rate of both referents).
5 and its interaction with referent position, we again used a
1 Finally, for the Bayesian model, the predicted interpreta-
0 sum-coding numeric representation of the verb bias
y 2 predictor.Weconductedtwolikelihood-ratiotestsbetween tion bias results from combining estimates of the pro‐
uar mixed-effects models differing only in the presence or babilities utilised by both of these models: the prior
n probability for next-mention of a referent P(referent) and
a absence of a verb bias main effect or interaction. The
J
6 likelihood-ratio test showed no main effect of verb bias the probability of producing a pronoun when re-mention-
2
6 (p = 0.56, 1 d.f.) nor a referent position × verb bias ingthereferentP(pronoun∣referent),scaledbythenormal-
0
6: interaction (p = 0.95, 1 d.f.).7 ising probability P(pronoun) which, per Equation (3), is
at 1 As such, the lack of effect of semantic biases on the numerator summed over the two referents in question.
] We then compare these three predicted interpretation
y pronoun production previously shown for unambiguous
rsit contexts is found in ambiguous contexts as well: Even values against the observed pronoun interpretation biases
e P(referent∣pronoun), as measured by the data collected in
niv when the comprehender’s ability to successfully interpret the pronoun-prompt condition.
U thepronoun isatstake,pronoun productionbiasesarenot
ell affected by the same semantically driven contextual Weexpectthatthepredictionsofallmodelswillreveal
n some degree of correlation with the observed data: The
k factors that have been demonstrated to influence pronoun
uc Mirror model should capture the differences in biases
B interpretation. Counter to the intuition that speakers will
[ between subject and non-subject referents, whereas the
y pronominalise mentions of referents in just those cases in
b Expectation model should capture differences across
ed whichcomprehenderswillbebiasedtoassignpronounsto context type. Crucially, however, in combining the biases
d those same referents, it is most striking that we find the
a captured by both models, we expect the Bayesian model
o
nl same rates of pronominalisation in contexts that give rise to be more highly correlated than either of the other
w
to strongly divergent next-mention biases. Instead, the
o models alone. Figure 3 shows the observed and model-
D
evidence just surveyed suggests that grammatical role is
predicted rates at which a pronoun will be interpreted to
the critical factor in determining pronoun production
refer to referents in the two grammatical roles across the
biases, without regard to the bias that the comprehender
three verb bias conditions. As can be seen, the observed
will bring to the interpretation process after factoring in
values are most consistently matched by the Bayes-
prior, top-down next-mention expectations. derived values.8 For the statistical analysis, we use a
Finally, as previously mentioned, we can use the data linear model to test the correlation between the values
collected here to test our Bayesian Hypothesis, i.e., that observed in the pronoun-prompt condition and the values
Equation (3) captures the relationship between pronoun under the three different models. The correlation is
productionandpronouninterpretationbiases.Wecompare performed over participant and item means; each particip-
the predictions of the Bayesian model and two competing ant (or item) contributes a value for the four pronoun
models against the actual interpretation biases witnessed, interpretation estimates in each of the verb bias × referent
foreachparticipantanditem.Thefirstcompetingmodelis combinations. We excluded data from participants (or
what we call the Expectancy model, according to which items) for which the Mirror- and Bayes-derived values
the interpretation bias towards a referent equals the could not be estimated—specifically if a participant’s no-
probability that the referent gets re-mentioned. This pronoun-prompt responses for a particular verb type
prediction follows from the Expectancy Hypothesis of contained no mentions of a particular referent or no
Arnold (2001), as well as the Hobbsian treatment of pronouns for either referent; in both cases computing the
Language, Cognition and Neuroscience 919
Expectancy
1.0 Mirror
Bayes
0.8 Observed
y
bilit 0.6
a
b 0.4
o
r
P
0.2
0.0
IC1:Subj IC2:Subj NonIC:Subj IC1:NonSubj IC2:NonSubj NonIC:NonSubj
Figure3. EstimatedandobservedpronouninterpretationbiasesacrossconditionsandreferentsinExperiment1.Forexample,thebars
in the “IC1:Subj” group show the predicted rates at which pronouns would be interpreted as referring to the subject referent in IC1
contexts under (1) the Expectancy model, (2) the Mirror model, and (3) the Bayesian model; these rates can be compared to (4) the
Observed rate. Errorbars represent standard error over participantmeans.
Table 1. Correlations between observed data and model cannotbeconflated.Sometimesnon-subjectsservetherole
predictions, byparticipants andbyitems. of sentence topic (Lambrecht, 1994, p. 118); for instance
5 the sentence Few people amaze Brittany intuitively pre-
1 Obs∼Mirror Obs∼Expectancy Obs∼Bayes
0 dicates a property of Brittany and not of few people.
2
y Byparticipants R2= 0.59* R2=0.13* R2= 0.69* The idea that one of the functions of pronouns is to
ar Byitems R2= 0.69* R2=0.16* R2= 0.74*
u signal a continuation of the current topic—which we refer
n
Ja *Indicatessignificanceatorbelow0.001. to as the Topichood Hypothesis—offers an alternative
26 explanation of the production data that we have seen in
06 the foregoing experiments.Under thishypothesis, speakers
6: predicted probabilities of the Mirror and Bayesian models preferentially realise a continuing topic as a pronoun,
1
at would involve division by zero. whereas comprehenders mustinfer the identity ofthe topic
] The results are shown in Table 1. As predicted,
y from properties of the discourse context, including the
rsit whereasallofthemodelsarecorrelatedwiththeobserved grammatical roles occupied by the alternatives. On this
Unive danatda,mitoissttchoenBsiasyteenst-dfeitr.i9vedvaluesthatprovidetheclosest awnealfyinsids,atsheorenfeorme,otvheesddeocwlinninthgeragtreasmomfpatriocnaolmobinliaqluiseantieosns
ell hierarchy (subjects > objects > other referents) in fixed
n
ck Interlude: subjecthood versus topichood word order languages would therefore reflect the declining
u
B likelihood that an entity in that position is the topic, rather
[ The results of Experiment 1 and those of the previous
y than being related directly to grammatical role.10
b studies surveyed agree that the semantically driven next-
d Sothequestionbeforeusiswhetherproductionbiases
e mention biases that have been demonstrated to affect
ad interpretation do not influence production. On the other are really dictated by the grammatical roles that potential
o
nl hand, these results also agree that grammatical role does referents occupy or by the likelihood that a potential
w
o have an effect on production: Across experiments, rates of referent is the current topic. None of the experiments
D
pronominalised reference to the previous subject are carried out to date resolve the issue, since none have
substantially higher than for other grammatical roles. A manipulated the likelihood that a potential referent is the
grammatical role-based preference is not the only possible topic without also varying grammatical role. To examine
explanation for this pattern, however. In particular, several this question, we can take advantage of the fact that
authors haveclaimed thata central functionofpronounsis different syntactic constructions mark the potential for
to signal a continuation of the current topic (Ariel, 1990; topicality of their grammatical role occupants to different
Grosz et al., 1995; Gundel et al., 1993; Lambrecht, 1994; degrees, in some cases placing the presumed topic in a
inter alia). The sentence topic, a pragmatic, information- particular syntactic position (Davison, 1984; Gundel &
structural concept rather than a grammatical one, is Fretheim, 2004; Ward & Birner, 2004, inter alia).
commonly (albeit informally) characterised as the constitu- Consider the contrast between active and passive voice:
ent that expresses what the sentence is about, i.e., as
(6) a. Amanda amazed Brittany.
denoting the entity about which an utterance is primarily
b. Brittany was amazed by Amanda.
intended to expand the addressee’s knowledge (Gundel,
1974; Kuno, 1972; Lambrecht, 1994; Reinhart, 1981; Sentences (6a) and (6b) convey the same proposition.
Strawson, 1964, inter alia). While subject and topic are However, not only do they differ with respect to which
highlycorrelatedinEnglish—indeed,subjectpositionisthe entityisconsideredthedefaulttopic(thesubjectsAmanda
canonical place for a topic to appear—the two notions in (6a) and Brittany in (6b)), but they also differ with
920 H. Rohde and A. Kehler
respect to the likelihood that their respective subjects condition estimate the biases towards next mention that
serveasthetopic:Brittanyismorelikelytobethetopicin participants favour before they encounter any referring
(6b) than Amanda is in (6a). That is, whereby Amanda is expression. Based on the IC biases reported in previous
merelythedefaulttopicin(6a)outsideofalargercontext, studies, participants are predicted to rely primarily on the
the promotion of another constituent to the syntactic verb’s semantic bias in the no-pronoun condition and
subject (and hence, topical) position in (6b) constitutes a therefore write more continuations about the logical
much stronger signal that the subject is the topic; indeed subject Amanda than Brittany. Second, as before, if
establishing a non-Agent as a topic is commonly con- pronoun production is conditioned by subjecthood or
sidered to be one of the primary functions of the passive topichood, the Bayesian formulation predicts that provid-
(Givón, 1990; Shibatani, 1985, inter alia). ing a pronoun in each pronoun-prompt condition should
We can thus use the active–passive alternation to test pull the distribution of first mentions towards the subject
the hypothesis that manipulating the likelihood of poten- position as compared to the corresponding no-pronoun
tial referents being the topic will influence speakers’ condition.Third,theBayesiananalysisalsopredictsthat,in
biases to pronominalise even when grammatical position the pronoun condition, there will be a greater number of
is kept constant. We do this in Experiment 2. references to Amanda (the IC-congruent referent) in the
activecondition(7c)thaninthepassiveone(7d),sincethe
fact that Brittany is the surface subject of (7d) is expected
5 Experiment 2
1 tocounteracttheICbiastowardsAmanda.Finally,wewill
0
y 2 Basedontheideathatbeingthesubjectofapassivevoice test the correlation between the actual interpretation biases
ar clause is a stronger indicator of topichood than being the measuredinthepronounconditionandthevaluespredicted
u
n subject of an active voice clause, we ask whether this by Equation (3) using data collected in the no-pronoun
a
6 J differencehasaneffectonrateofpronominalisationofthe condition, as we did in Experiment 1.
2 subject across constructions. Consider the story continua-
6
0 tion prompts in (7), which describe the same event in the
6:
1 activeandpassivevoice. Followingstandardterminology,
y] at we will henceforth refer to Amanda as the logical subject MPaertthicoidpsants
ersit i(n7aa)llafnodur(p7rco)m(patnsd,alnidkeAwmisaendBariattsatnhyesinyn(t7acbt)icasnudbj(e7cdt)i)n. Forty-two monolingual English-speaking undergraduates
niv Because the verb amaze in (7) is known to be a subject- from UC San Diego participated in the experiment for
ell U bcaiausseedoIfCtheveervbe,nittiinsaAllmcaasnedsa. who is implicated as the extra credit in Linguistics courses.
n
ck Materials and procedure
u (7) Manipulation of topichood and continuation
B For the experimental items, each context sentence men-
d by [ a. Apmroanmdpatamazed Brittany. ________________ tbiioanseeddtIwCovreerfber,enastsiinn(a7n).evTehnet dtwesocrciboemdpwetiitnhgarseufebrjeenctts-
de [Active, no-pronoun prompt]
a were of the same gender, counterbalanced between male
o b. Brittany was amazed by Amanda. ____________
nl and femalenames. Twenty verbs were taken from a set of
w [Passive, no-pronoun prompt]
o subject-biased IC verbs that have been used in previous
D c. AmandaamazedBrittany.She _______________
studies on IC: aggravate, amaze, amuse, annoy, astonish,
[Active, pronoun prompt]
bore, charm, deceive, disappoint, exasperate, fascinate,
d. BrittanywasamazedbyAmanda.She_________
frighten, humiliate, infuriate, inspire, intimidate, irritate,
[Passive, pronoun prompt]
offend, scare and surprise. Voice and prompt type varied
If production biases are sensitive specifically to gram- within participants and within items.
matical role, then the rate at which participants produce Theexperimentconsistedof68items:20experimental
pronominalised references to the syntactic subject in items interleaved with 24 items for an unrelated experi-
the no-pronoun condition is predicted to be the same ment and 24 additional fillers. The stimuli for the
across (7a) and (7b). If the Topichood Hypothesis is interleaved experiment contained sentences with transfer-
correct, however, we expect the rate at which partici- of-possession verbs followed either by a no-pronoun
pants pronominalise references to the syntactic subject prompt or an ambiguous pronoun prompt (John brought
in the passive (7b) to be higher than the rate at which a glass of water to a guy. (He)_______). The additional
they pronominalise such references in the active fillers consisted of context sentences containing non-IC
case (7a). verbs followed by intersentential connectives, pronoun or
Our study will also examine a set of secondary no-pronoun prompts. Story continuations were collected
predictions. First, recall that the first-mention statistics using the same web-based interface that was used in
revealed by the continuations in the no-pronoun-prompt Experiment 1.
