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Establishing propositional truth-value in counterfactual and real-world contexts during sentence comprehension: differential sensitivity of the left and right inferior frontal gyri.

15 Feb 2012-NeuroImage (Academic Press)-Vol. 59, Iss: 4, pp 3433-3440

TL;DR: The fMRI study investigated the neural circuits that are sensitive to the propositional truth-value of sentences about counterfactual worlds, aiming to reveal differential hemispheric sensitivity of the inferior prefrontal gyri tocounterfactual truth- Value and real-world truth- value.

AbstractWhat makes a proposition true or false has traditionally played an essential role in philosophical and linguistic theories of meaning. A comprehensive neurobiological theory of language must ultimately be able to explain the combined contributions of real-world truth-value and discourse context to sentence meaning. This fMRI study investigated the neural circuits that are sensitive to the propositional truth-value of sentences about counterfactual worlds, aiming to reveal differential hemispheric sensitivity of the inferior prefrontal gyri to counterfactual truth-value and real-world truth-value. Participants read true or false counterfactual conditional sentences ("If N.A.S.A. had not developed its Apollo Project, the first country to land on the moon would be Russia/America") and real-world sentences ("Because N.A.S.A. developed its Apollo Project, the first country to land on the moon has been America/Russia") that were matched on contextual constraint and truth-value. ROI analyses showed that whereas the left BA 47 showed similar activity increases to counterfactual false sentences and to real-world false sentences (compared to true sentences), the right BA 47 showed a larger increase for counterfactual false sentences. Moreover, whole-brain analyses revealed a distributed neural circuit for dealing with propositional truth-value. These results constitute the first evidence for hemispheric differences in processing counterfactual truth-value and real-world truth-value, and point toward additional right hemisphere involvement in counterfactual comprehension.

Topics: Counterfactual conditional (63%), Counterfactual thinking (63%), Proposition (55%), Sentence (54%)

Summary (3 min read)

Introduction

  • Language is a computationally remarkable, uniquely human system, not to mention their principal and most efficient means of communication.
  • These findings testify to the fact that an extended network of brain regions is sensitive to sentence truth-value, even if participants are not explicitly instructed to establish truth-value.

Participants

  • Twenty-eight right-handed students (14 males, mean age=22.9 - years) participated in this study for monetary compensation.
  • All participants were native Spanish speakers, had normal or corrected-to- normal vision, and gave written informed consent.
  • Participants had no neurological or psychiatric disorders, nor had they seen the materials before in an earlier experiment.
  • Four participants were excluded from the final analysis due to excessive movement during the experiment.

Development and pretest of materials

  • Materials were identical to those used by Nieuwland and Martin (2012), and were selected from 133 Spanish sentence quadruplets with two counterfactual and two real-world sentences (see Table 1).
  • Counterfactual sentences described hypothetical consequences of common-knowledge historical events not having taken place, whereas real-world sentences described actual consequences of these events.
  • The authors first established the expectedness of critical words.
  • Twenty students of the University of the Basque Country completed one of two lists with one version of each item truncated before the critical word.
  • Twentyfour different students evaluated one of four counterbalanced sentence lists containing only one condition per quadruplet, and decided whether the sentences were true (1=False, 7=True), skipping any they could not evaluate.

Experimental procedure

  • While inside the scanner, participants read sentences presented via back-projection onto the middle of the screen, and would view the stimuli via a mirror attached to the head coil.
  • Moreover, while Tesink et al. reported effects of truth-value of single sentences, the Menenti et al. study involved multi-sentence stories rather than single sentences, and the reported coordinates in that study might thus not be optimal for the comparisons in the current study.
  • FMRI data acquisition, preprocessing and analysis Imaging took place on a 3-T MR scanner (Siemens TrioTim) with echoplanar imaging capability.
  • Each subject then viewed one of the four counterbalanced sentence lists with the sentence trials and fixation trials, across six functional runs.
  • The explanatory variables were modeled as a fixed response (box-car) waveform temporally convolved with the canonical HRF along with its temporal derivative (Friston et al., 1998), while controlling for serial correlations.

Region-of-interest analysis

  • Given the a priori hypothesis about the role of the IFG, a region-ofinterest (ROI) analysis was performed using the Marsbar toolbox (Brett et al., 2002) by extracting average parameter estimates per condition and per subject for 2 LIFG ROIs and their right hemisphere counterparts.
  • These ROIs were based on the results of a related study that reported activations within different subregions of the left and right IFG (pars orbitalis/triangularis; BA 45/47) for world knowledge violations in healthy adults during sentence processing (Tesink et al., 2011; see also Tesink et al., 2009, for similar results).
  • A 2(Context: counterfactual, real-world) by 2(Propositional truth-value: true, false) by 2(hemisphere: left, right) repeated measures analysis of variance was performed on the extracted parameter estimates per ROI.

Whole-brain analysis

  • The whole-brain analysis did not reveal any significant clusters for the interaction between Context and Propositional truth-value.
  • Consistent with the absence of a significant Context by Propositional truth-value interaction effect, the false minus true contrast elicited similar activation increases for counterfactual and real-world sentences (see Table 3 and Fig. 2).
  • These clusters were located in left and right inferior frontal gyrus (LIFG and RIFG, BA 45 and BA 47) extending into the middle frontal gyrus (MFG, BA 8/9), left middle temporal gyrus (MTG, BA 21), medial parts of the superior frontal gyrus (SFG, BA 6/8), and the left inferior parietal lobule (IPL, BA 40).
  • Consistent with the main effect of context, the contrast (Counterfactual False>Real-world False) elicited a significant cluster in LMTG (k=440, peak voxel coordinates [−48 −32 4]), as did the contrast (Counterfactual True>Real-world True) (k=1421, peak voxel coordinates [−50 −24 −14]).

ROI analysis

  • Differences in parameter estimates corresponding to the effect of truth-value (false minus true sentences) per sentence type and ROI are plotted in Fig. 1b.
  • This differential effect of truth-value in the right BA 47 ROI for the two sentence types was of a quantitative nature rather than a qualitative: the effect of truth-value was statistically significant for each sentence type, but it was stronger in counterfactual sentences (F(1,23)=6.83, pb .001) than in real-world sentences (F(1,23)=2.21, p=.037).
  • This difference was driven mainly by a large response to counterfactual false sentences, which was larger than the response to real-world false sentences (F(1,23)=3.59, p=.002), while the responses to counterfactual true and real-world true sentences did not differ (F(1,23)= 1.06, p=.31).

Discussion

  • This fMRI study investigated the neural circuits that are sensitive to the propositional truth-value of sentences about counterfactual worlds or about the real world, and aimed to reveal hemispheric differences between the inferior prefrontal gyri in processing counterfactual truth-value and real-world truth-value.
  • No such pattern was found for the left and right BA 45 ROIs.
  • The current larger sensitivity of the RIFG to counterfactual truth-value than to real-world truth-value may thus reflect increased semantic processing due to the semantic complexity of the counterfactual false sentences.
  • The larger effect in the RIFG for counterfactual truth-value is consistent with right hemisphere activations associated with comprehending contextual and figurative meaning and with complex sentences and discourse level processing (e.g., Kuperberg et al., 2006; Stringaris et al., 2006; Xu et al., 2005 see Jung-Beeman, 2005; Mason and Just, 2006).
  • First of all, these differences occurred before the critical words, and their effects were accounted for by separate.

MFG

  • Contexts may have been the use of historical counterfactual conditionals.
  • Whereas Menenti et al. created novel and unfamiliar fictional stories, alternative endings to known historical events may be more easily computed, for example because relevant information is also part of their real-world knowledge (e.g., the fact that the Soviets were also making substantial progress in landing somebody on the moon at the time that the USA managed to do so).
  • In the current study, counterfactual and real-world sentences elicited similar effects of truth-value in the left middle temporal gyrus.
  • These results may reflect increased semantic retrieval of relevant information in long-term memory (e.g., of the correct information) from medial temporal lobe, governed by the inferior prefrontal gyri (e.g., Bookheimer, 2002; Hagoort et al., 2009; Lau et al., 2008).
  • Interestingly, activity increases in this region have been reported for syntactic errors but not for semantic anomalies (they may even result in relative deactivations; e.g., Hagoort et al., 2004; Nieuwland et al., 2007, 2011; Tesink et al., 2009).

Acknowledgments

  • This research was supported by a Plan Nacional research grant from the Spanish Ministry of Science and Innovation (grant number PSI2010-18087) to MSN.
  • Many thanks to Javi Miqueleiz for help with stimulus construction, to Natalia Barrios and Larraitz Lopez for help with data collection, and to two anonymous reviewers and Andrea Eyleen Martin for comments on an earlier version of this manuscript.

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Establishing propositional truth-value in counterfactual and real-world contexts
during sentence comprehension: Differential sensitivity of the left and right inferior
frontal gyri
Mante S. Nieuwland
Basque Center on Cognition, Brain and Language (BCBL), Paseo Mikeletegi 69-2, 20009, Donostia-San Sebastian, Spain
abstractarticle info
Article history:
Received 22 September 2011
Revised 24 October 2011
Accepted 4 November 2011
Available online 13 November 2011
Keywords:
Language comprehension
Real-world knowledge
Propositional truth-value
Counterfactuals
fMRI
LIFG
RIFG
What makes a proposition true or false has traditionally played an essential role in philosophical and linguis-
tic theories of meaning. A comprehensive neurobiological theory of language must ultimately be able to ex-
plain the combined contributions of real-world truth-value and discourse context to sentence meaning. This
fMRI study investigated the neural circuits that are sensitive to the propositional truth-value of sentences
about counterfactual worlds, aiming to reveal differential hemispheric sensitivity of the inferior prefrontal
gyri to counterfactual truth-value and real-world truth-value. Participants read true or false counterfactual
conditional sentences (If N.A.S.A. had not developed its Apollo Project, the rst country to land on the
moon would be Russia/America) and real-world sentences (Because N.A.S.A. developed its Apollo Proj ect,
the rst country to land on the moon has been America/Russia) that were matched on contextual constraint
and truth-value. ROI analyses showed that whereas the left BA 47 showed similar activity increases to coun-
terfactual false sentences and to real-world false sentences (compared to true sentences), the right BA 47
showed a larger increase for counterfactual false sentences. Moreover, whole-brain analyses revealed a dis-
tributed neural circuit for dealing with propositional truth-value. These results constitute the rst evidence
for hemispheric differences in processing counterfactual truth-value and real-world truth-value, and point
toward additional right hemisphere involvement in counterfactual comprehension.
© 2011 Elsevier Inc. All rights reserved.
Introduction
Language is a computationally remarkable, uniquely human system,
not to mention our principal and most efcient means of communica-
tion. It is often assumed that language evolved as an adaptation for
communication about the world (e.g., Pinker and Bloom, 1990). The ex-
change of information through statement of fact routinely affords veri-
cation processes through which people are able to agree or disagree
with what they read or hear, and draws upon our capacity to recall
word meanings and everyday facts and events (i.e., declarative memo-
ry; Eichenbaum, 2000). Conditions that make a proposition true or false
have traditionally played an essential role in philosophic al and linguis-
tic theories of meaning (e.g., Montague, 1974; Tarski, 1944). Yet, while
language retains its power for exchanging information about the world,
its productive and combinatorial nature enables us to think and talk
about concepts beyond the real world. One prominent example of this
cognitive ability is counterfactual reasoning about what is in fact false
as if it were true (e.g., If China had entered the Vietnam war,
then…”), which is pervasive in everyday life (e.g., Byrne, 2002;
Kahneman & Miller, 1986; Roese, 1997), and considered one of the
hallmarks of complex reasoning skills (e.g., Braine and O'Brien, 1991;
Byrne & Johnson-Laird, 2009). Counterfactual comprehension is often
thought to require keeping in mind both what is true and what is
false (e.g., Byrne, 2002, 2007; for discussion see Evans, 2006; Evans et
al., 2005). This makes counterfactual comprehension an interesting
test-case for identifying the brain regions that are sensitive to proposi-
tional truth-value; whereas establishing the truth-value of a regular de-
clarative sentence requires a straightforward mapping of its
propositional meaning onto real-world knowledge that is stored in
long-term memory, establishing counterfactual truth-value requires
the online construction of a contextually relevant interpretation by
temporarily bracketing factual knowledge about the real world (e.g.,
Searle, 1975; Stalnaker, 1968). The current fMRI study aims to unravel
the neural circuits that are sensitive to propositional truth-value, as
expressed in sentences about counterfactual worlds or about the real
world.
According to cognitive theories of text comprehension (e.g.,
Gernsbacher, 1997; Kintsch, 1988; Myers and O'Brien, 1998),
comprehension of counterfactual language requires the suppression
or inhibition of automatically activated world knowledge. All infor-
mation in memory that is related to unfolding linguistic input is
initially activated, and this network of co-activations is subsequently
pruned so that only the information that is most relevant to the
NeuroImage 59 (2012) 34333440
E-mail address: m.nieuwland@bcbl.eu.
1053-8119/$ see front matter © 2011 Elsevier Inc. All rights reserved.
doi:10.1016/j.neuroimage.2011.11.018
Contents lists available at SciVerse ScienceDirect
NeuroImage
journal homepage: www.elsevier.com/locate/ynimg

ongoing interpretation is kept active. Similar assumptions have been
made in neurocognitive accounts of semantic processing during
language comprehension (e.g., Bookheimer, 2002; Hagoort, 2005;
Hagoort et al., 2009; Lau et al., 2008): word-elicited semantic informa-
tion is selected for message-level semantic integration through the acti-
vation of relevant concepts and inhibition of competing concepts,
drawing upon activity in and interaction between the temporal and in-
ferior prefrontal brain regions that subserve semantic memory process-
es (see also Badre and Wagner, 2002; Thompson-Schill et al., 1997).
A canonical nding supporting the role of the left inferior frontal
gyrus for recruiting factual world knowledge during sentence com-
prehension was reported by Hagoort et al. (2004). In an fMRI
experiment, sentences that were regarded by Dutch participants as
false (e.g., Dutch trains are white) elicited common activity
increases in the left inferior frontal gyrus (LIFG, BA 45/47) as
sentences that contained lexical-semantic anomalies (e.g., Dutch
trains are sour, which is not only false but also makes no sense
given the semantic constraints of the words trains and sour), each
compared to true sentences (e.g., Dutch trains are yellow). Later
studies replicated and extended these ndings by showing that
world knowledge violations elicit additional activations in other
brain regions, most notably in right inferior prefrontal cortex, middle
and superior prefrontal gyrus, middle temporal gyrus, and the inferior
parietal lobule (e.g., Groen et al., 2010; Menenti et al., 2009; Tesink et
al., 2009, 2011). These ndings testify to the fact that an extended
network of brain regions is sensitive to sentence truth-value, even if
participants are not explicitly instructed to establish truth-value.
These ndings are consistent with a recent neurocognitive frame-
work of language comprehension, the Memory-Unication-Control
framework (e.g., Hagoort, 2005; Hagoort et al., 2009), which posits
that the left inferior frontal cortex (with additional support from
other areas) has top-down control over the combinatorial semantic
processes that compose multi-word utterances from word-elicited in-
formation as represented by the left middle temporal cortex. Moreover,
knowledge from different sources and modalities (e.g., speaker identi-
ty, real-world knowledge, discourse context) is immediately brought to
bear on utterance interpretation, by the same brain system that com-
bines the meanings of individual words into a larger whole (Hagoort,
2005; see also Hagoort and Van Berkum, 2007). However, while
many event-related potential (ERP) studies have revealed a rapid inter-
action between world knowledge and discourse context (e.g., Hald et
al., 2007; Nieuwland and Kuperberg, 2008; Nieuwland and Van
Berkum, 2006; Van Berkum et al., 2008, 2009; for eye-tracking and
ERP results on online counterfactual comprehension, see Ferguson et
al., 2008; Ferguson and Sanford, 2008), the neural mechanisms that un-
derlie the unication of real-world knowledge with discourse context
remain understudied. A comprehensive neurobiological theory of lan-
guagemustultimatelybeabletoexplainthecombinedcontributions
of real-world truth-value and discourse context.
In the only fMRI study thus far that examined these issues
(Menenti et al., 2009), sentences that
without any context were
regarded as false or true (e.g., Donald Duck's nephews are thieves/
boy scouts) were preceded by either a counterfactual (i.e. ctional)
context that was congruent with the false sentences (e.g., a story
about early sketches wherein the three nephews were depicted as
young bad boys who rob old ladies) or by a neutral context that
was congruent with the true sentences (e.g., a story about early
sketches where they were depicted as helping old ladies). The results
showed that the impact of world knowledge violations (false minus
true sentences) was more reduced due to counterfactual context in
the RIFG than in the LIFG: world knowledge violations did not elicit
effects in RIFG but remained to elicit signicant effects in the LIFG
despite the counterfactual context. Additionally, in the left angular
gyrus, the effect of the world knowledge violation was actually
reversed following the counterfactual context, suggesting that this
brain region was most sensitive to discourse coherence. The authors
offered a tentative interpretation that whereas the LIFG continues to
relate incoming information to prior world knowledge, the RIFG is
more sensitive to whether incoming information is congruent with
the discourse (however, counterfactual context did not reverse the
effect of world knowledge in the RIFG). This functional division of
labor between LIFG and RIFG is congruent with a body of literature
on right hemisphere involvement in high-level aspects of language
(e.g., discourse processing and pragmatic language comprehension;
Bookheimer, 2002; Jung-Beeman, 2005; Mason and Just, 2006; Ferstl
et al., 2008). One inuential account holds that the right hemisphere
processes incoming information more coarsely and is therefore more
sensitive to unusual or novel semantic relationships (e.g., Jung-
Beeman, 2005). Semantic selection processes, which inhibit compet-
ing concepts to select one concept for message-level semantic
integration, may then draw upon the RIFG more strongly when the
information that needs to be inhibited is more active in the right
hemisphere (e.g., Jung-Beeman, 2005; see also Faust and
Gernsbacher, 1996, for discussion). Perhaps in a similar vein, neuro-
cognitive research on reasoning has revealed right lateral prefrontal
activations when participants inhibit their world knowledge in
order to arrive at a logically sound conclusion (Goel and Dolan,
2003; see also Goel, 2007).
The current fMRI study therefore aimed to address the following
question: Are the LIFG and RIFG differentially engaged in balancing the
recruitment of information in long-term memory with the online con-
struction of a discourse-relevant and contextualized interpretation? Ad-
ditionally, and more generally, what brain regions are sensitive to
sentence truth-value? This study aims to answer those questions in the
context of counterfactual sentence comprehension, by directly compar-
ing the neural processing consequences of sentences that are false with
regard to a hypothetical, counterfactual world with those of sentences
that are false with regard to the current real-world knowledge. Partici-
pants read counterfactual and real-world sentences in which a specic
critical word, belonging to a word pair, rendered the sentence false or
true. For each word pair, one word rendered the counterfactual sentence
true while rendering the real-world sentence false, and vice versa for the
other word (see Tables 1 and 2). The contextual constraints were
matched for counterfactual and real-world sentences, so that, on aver-
age, critical words that rendered sentences true were equally expected
for each sentence type, and so that these sentence types were similar
in truth-value (as had been established in an independent sentence com-
pletion pre-test and truth-value rating pre-test, respectively; see
Materials and methods section). The results from an earlier ERP study
with these materials (Nieuwland and Martin, 2012) showed that
words that rendered sentences false elicited identical N400
effects (compared to words that rendered sentences true) in counterfac-
tual sentences and real-world sentences. These results suggest that, if de-
scribed consequences are true and predictable given the counterfactual
premise, real-world knowledge does not impede or delay counterfactual
comprehension, at least at the moment that propositional truth-value
can be established. However, fMRI might reveal differences between
counterfactual or real-world sentence comprehension processes that
occur at a wider timescale and account for the larger network that is en-
gaged for establishing propositional truth-value in both contexts.
The current study is the
rst to deal directly with the comprehen-
sion of counterfactual conditional sentences. The main prediction of
the current study is that the LIFG and RIFG will be differentially sen-
sitive to real-world and counterfactual truth-value: the RIFG being
more sensitive to counterfactual truth-value than the LIFG, but
being equally or perhaps less sensitive to real-world truth-value
(e.g., Hagoort et al., 2004).
An additional, more general objective of this study is to reveal the
neural circuits that are sensitive to truth-value, using a design where
propositional truth-value of the two sentence types hinges on oppo-
site pairs of critical words, thereby controlling for the impact of differ-
ences in lexical-associative factors between words in true and false
3434 M.S. Nieuwland / NeuroImage 59 (2012) 34333440

sentences. Compared to true sentences, false sentences are predicted
to increase activation in left and right inferior prefrontal gyrus, and
possibly in left middle frontal gyrus, left middle temporal gyrus and
in left inferior parietal cortex (e.g., Groen et al., 2010; Hagoort et al.,
2004; Menenti et al., 2009; Tesink et al., 2009, 2011).
Materials and methods
Participants
Twenty-eight right-handed students (14 males, mean age=22.9 -
years) participated in this study for monetary compensation. All par-
ticipants were native Spanish speakers, had normal or corrected-to-
normal vision, and gave written informed consent. Participants had
no neurological or psychiatric disorders, nor had they seen the mate-
rials before in an earlier experiment. Four participants were excluded
from the nal analysis due to excessive movement during the
experiment.
Development and pretest of materials
Materials were identical to those used by Nieuwland and Martin
(2012), and were selected from 133 Spanish sentence quadruplets
with two counterfactual and two real-world sentences (see
Table 1). Critical words were predicates, nouns or proper names,
and never sentence-nal. Counterfactual sentences described hypo-
thetical consequences of common-knowledge historical events not
having taken place, whereas real-world sentences described actual
consequences of these events. The two sentence types differed in
three respects: counterfactuals started with the conditional Si, con-
tained a negative premise, and involved conditional verb tense, real-
world sentences started with Como (because), were afrmative,
and contained no conditional verb tense.
We rst established the expectedness of critical words. Twenty
students of the University of the Basque Country completed one of
two lists with one version of each item truncated before the critical
word. They were instructed to complete the sentence with the rst
sensible word coming to mind. Cloze value was computed as the per-
centage of participants who used the intended critical word.
We subsequently determined whether sentences (truncated after
the critical word) were, on average, regarded as true or false. Twenty-
four different students evaluated one of four counterbalanced sen-
tence lists containing only one condition per quadruplet, and decided
whether the sentences were true (1=False, 7=True), skipping any
they could not evaluate.
Based on these results, we excluded quadruplets with low cloze
value, containing true/false sentences rated below/over 4, or sen-
tences skipped by more than two participants. In the ultimate set of
120 quadruplets, true and false sentences had similar cloze values
and ratings across conditions (see Table 1), and critical words were
matched for mean log frequency (CT/RWT =1.44/1.55; p=.11;
Davis & Perea, 2005) and word length (CT/RWT=6.65/6.89 letters;
p=.24). Average counterfactual sentence length was 16.2 words
(SD=2.8), and real-world sentence length was 14.6 words
(SD=2.7).
We created four counterbalanced lists so that each sentence
appeared in only one condition per list, but in all conditions equally
often across lists. Within each list, items were pseudo-randomly
mixed with 60 ller sentences to limit succession of identical sen-
tence types while matching trial types on average list position. The
ller sentences did not start with Si or Como
, and consisted of
two clauses separated by a comma.
Experimental procedure
While inside the scanner, participants read sentences presented
via back-projection onto the middle of the screen, and would view
the stimuli via a mirror attached to the head coil. They were
instructed to minimize movement and read the sentences attentively,
and to answer yes/no comprehension questions that appeared after
some of the sentences with a left- or right-hand button-press (left-
or right-hand assignment for yes/no was counterbalanced across
participants).
Four trial lists were used (each subject was pseudorandomly
assigned to one of the four trial lists, so that the lists were equally dis-
tributed across subjects). For the rst list, 30 items from each condi-
tion were pseudo-randomly mixed with the ller sentences such
that no trial type occurred more than three times consecutively and
trials of each type were matched on average list position. The other
Table 1
Example sentences and approximate translations with average truth-value rating and
cloze value of the critical word for each condition.
This table is adapted from Nieuwland and Martin (2011).
Condition Example sentences Mean rating
of truth-value
Mean cloze
value (%)
Counterfactual
True (CT)
Si la N.A.S.A. no hubiera desarrollado
su proyecto Apollo, el primer país en
pisar la luna habría sido
Rusia
seguramente.
5.62 (.97) 68 (22)
If N.A.S.A. had not developed its
Apollo Project, the rst country to
land on the moon would have been
Russia surely.
Counterfactual
False (CF)
Si la N.A.S.A. no hubiera desarrollado
su proyecto Apollo, el primer país en
pisar la luna habría sido
América
seguramente.
1.68 (.74)
If N.A.S.A. had not developed its
Apollo Project, the rst country to
land on the moon would have been
America surely.
Real-World
True (RWT)
Como la N.A.S.A. desarrolló su
proyecto Apollo, el primer país en
pisar la luna ha sido
América
seguramente.
5.50 (1.03) 65 (25)
Because N.A.S.A. developed its
Apollo Project, the rst country to
land on the moon was
America
surely.
Real-World
False (RWF)
Como la N.A.S.A. desarrolló su
proyecto Apollo, el primer país en
pisar la luna ha sido
Rusia
seguramente.
1.55 (.64)
Because N.A.S.A. developed its
Apollo Project, the rst country to
land on the moon was
Russia
surely.
Filler sentence La gastronomía vasca está muy bien
considerada, es conocida en todo el
mundo.
Basque gastronomy is highly
regarded, it is known around the
world
Note. Standard deviations are given in parentheses. Critical words are underlined for
expository purposes. For truth-value rating, 1=False, 7= True.
Table 2
Schematic representation of the regressors corresponding to the different sentence
parts.
Counterfactual
Context
5. If N.A.S.A. had not developed its Apollo Project, the
rst country to land on the moon would have been
1. Russia
surely.
5. If N.A.S.A. had not developed its Apollo Project, the
rst country to land on the moon would have been
2. America
surely.
Real-World
Context
6. Because N.A.S.A. developed its Apollo Project, the
rst country to land on the moon was
3. America
surely.
6. Because N.A.S.A. developed its Apollo Project, the
rst country to land on the moon was
4. Russia
surely.
3435M.S. Nieuwland / NeuroImage 59 (2012) 34333440

lists were derived from the rst by rotating the trial types. The total of
180 sentences was divided into 6 sessions (presented in xed-order
across trial lists) of approximately 8 min each. Following the third
session, participants exited the scanner for a short break.
Participants silently read sentences presented in black letters on a
light-gray background. The rst clause was presented as a whole for
4000 ms, followed by a xation cross and blank screen each for
500 ms, and the second clause was presented word-by-word
(screen-centered, 400 ms word duration, 200 ms inter-word-
interval). Following every nal word, a blank screen was presented
for 500 ms, followed by either a xation period of variable duration
(58s)orbyrst a yes/no comprehension question and then a xa-
tion period. During the xation period, participants xate on a cross
in the middle of the screen and awaited the start of the next trial. If
a comprehension question appeared, it was presented for 2 s, fol-
lowed by a response screen that disappeared upon button-press or
after 1 s. The questions only served to keep participants more atten-
tive. They always probed their world knowledge related to words in
the sentence (e.g., Does N.A.S.A. have a headquarters in Houston?)
but did not probe knowledge that was critical for understanding the
sentences, and did not probe about the counterfactual premise.
These 60 questions (30 requiring a yes button-press response)
were distributed across sentence types. Participants performed with
92% accuracy on average (range across subjects 7798%).
fMRI data acquisition, preprocessing and analysis
Imaging took place on a 3-T MR scanner (Siemens TrioTim) with
echoplanar imaging capability. Head motion was minimized using
pillows and cushions around the head. Each subject then viewed
one of the four counterbalanced sentence lists with the sentence trials
and xation trials, across six functional runs. Each functional run
lasted around 570 s during which whole head T2
-weighted EPI-
BOLD fMRI data were acquired using an interleaved even acquisition
EPI sequence (TR=2 s; TE =30 ms; ip angle =90°; 32 axial slices;
matrix size = 64 ×64; slice thickness =3 mm; slice gap=0.75 mm;
transverse orientation acquisition; isotropic voxel-size=
3×3×3 mm
3
). After the functional runs, subjects underwent one
high-resolution 3D structural scan, using a T1-weighted MPRAGE se-
quence (176 transverse slices; volume TR=2530 ms; TE =2.97 ms;
TI=1100 ms; transverse orientation acquisition; ip angle = 7°;
slice matrix=256×256; slice thickness=1 mm, slice gap =0.5 mm).
Image preprocessing and statistical analysis was performed using
the SPM8 software (http://www.l.ion.ucl.ac.uk). The functional
EPI-BOLD contrast images were realigned, and the mean of realigned
images was co-registered with the corresponding structural MRI by
using mutual information optimization. These images were subse-
quently slice-time corrected, spatially normalized (images were re-
sampled with a 2 × 2 ×2 mm3 resolution), transformed into a com-
mon space (MNI-T1 template), and spatially ltered with an isotropic
3D Gaussian kernel (10 mm FWHM). The data were analyzed using
the general linear model and statistical parametric mapping. We in-
cluded the following explanatory variables (see Table 2, for a sche-
matic representation): each of the four critical conditions
(1=Counterfactual True, 2=Counterfactual False, 3 =Real-world
True, 4 = Real-world True) modeled separately from the onset of
the critical word with a duration extending to the end of the sentence
including the sentence-nal word, counterfactual context modeled
from the onset of each counterfactual sentence with a duration
extending to the offset of the pre-critical word (pooled across coun-
terfactual true and false sentences because they were identical up to
the critical word, number 5 in Table 2), real-world context modeled
from the onset of each real-world sentence with a duration up
extending to the offset of the pre-critical word (pooled across real-
world true and false sentences because they were identical up to
the critical word, number 6 in Table 2). Importantly, pre-critical
word differences between counterfactual and real-world sentences
in presence/absence of negation and in sentence length can thus not
account for observed differences in the critical regions. The xation
period was modeled from the onset of the xation mark until it disap-
peared from the screen. Effects of no-interest included one regressor
that pooled all ller sentences (modeled from sentence onset to off-
set), one regressor for the comprehension question and response
screen, and additional regressors for session and subject effects. The
explanatory variables were modeled as a xed response (box-car)
waveform temporally convolved with the canonical HRF along with
its temporal derivative (Friston et al., 1998), while controlling for se-
rial correlations. Low-frequency noise was removed with a high-pass
lter (time constant 128 s).
Region-of-interest analysis
Given the a priori hypothesis about the role of the IFG, a region-of-
interest (ROI) analysis was performed using the Marsbar toolbox
(Brett et al., 2002) by extracting average parameter estimates per
condition and per subject for 2 LIFG ROIs and their right hemisphere
counterparts. These ROIs were based on the results of a related
study that reported activations within different subregions of the
left and right IFG (pars orbitalis/triangularis; BA 45/47) for world
knowledge violations in healthy adults during sentence processing
(Tesink et al., 2011; see also Tesink et al., 2009, for similar results).
1
Signal was sampled from 2 spherical ROIs with a 10 mm radius cen-
tered on coordinates [ 44 29 12] and [36 268] for BA 45 and 47 re-
spectively (see Fig. 1a). These ROI center coordinates approximated
the average of peak voxel coordinates reported by Tesink et al.
(2011) (BA 45: [ 40 30 4] and [ 44 28 14], BA 47: [38 2210] and
[ 34 308]), with a small adjustment to avoid ROI overlap. A 2(Con-
text: counterfactual, real-world) by 2(Propositional truth-value: true,
false) by 2(hemisphere: left, right) repeated measures analysis of var-
iance (ANOVA) was performed on the extracted parameter estimates
per ROI.
Whole-brain analysis
In addition to ROI analyses, a whole-brain analysis was performed
to examine whether other brain regions were sensitive to counterfac-
tual and real-world truth-value. Average parameter estimates for the
explanatory variables were generated for each subject, and subjected
to a second-level random effects analysis with non-sphericity correc-
tion for correlated repeated measures, according to the 2 (Context:
counterfactual, real-world) by 2 (Truth-value: true, false) design.
The results of the random effects analyses were thresholded at
P=0.001 (uncorrected) and the cluster-size statistics were used as
the test statistic, only clusters are reported that were signicant at
P 0.05 corrected for multiple comparisons using the false discovery
rate (FDR; Genovese et al., 2002). All local maxima are reported as
MNI coordinates (Evans et al., 1993). Anatomical location and ap-
proximate Brodmann areas and were determined using the AAL tool-
box for SPM8 (Tzourio-Mazoyer et al., 2002) and with the xjView
toolbox (www.alivelearn.net/xjview8).
1
The coordinates were based on the results reported by Tesink et al. (2011) rather
than those reported by Hagoort et al. (2004) or Menenti et al. (2009). Hagoort et al.
reported coordinates that referred to the common activation for semantic violations
and world knowledge violations compared to the correct condition, and may thus
not be optimal for investigating the current effects of sentence truth-value (for exam-
ple, semantic violations and world knowledge violations are associated with different
peak activity coordinates, as reported by Tesink et al.). In addition, while Hagoort et
al. only reported a single cluster of common activation in the LIFG, the Tesink et al.
study revealed bilateral effects of truth-value for the same items. Moreover, while
Tesink et al. reported effects of truth-value of single sentences, the Menenti et al. study
involved multi-sentence stories rather than single sentences, and the reported coordi-
nates in that study might thus not be optimal for the comparisons in the current study.
3436 M.S. Nieuwland / NeuroImage 59 (2012) 34333440

Results
ROI analysis
Differences in parameter estimates corresponding to the effect of
truth-value (false minus true sentences) per sentence type and ROI
are plotted in Fig. 1b. Overall, false sentences elicited more activity
than true sentences in the BA 45 ROIs (F(1,23)=31.43, pb .001) and
in the B47 ROIs (F(1,23) =80.98, p b .001). In the BA 45 ROIs the effect
of truth-value was similar for counterfactual and real-world sen-
tences (F(1,23) = .005, p=.95), and did not differ between the left
and right ROI (F(1,23) =1.11, p =.30). In contrast, in the BA 47 ROIs
the effect of truth-value was larger for counterfactual sentences
than for real-world sentences (F(1,23)=5.08, p=.034), but this pat-
tern differed for the left and right ROI, as reected in a signicant
3-way interaction effect (F(1,23) = 4.58, p =.043). The effect of
truth-value was greater for counterfactual sentences than for real-
world sentences in the right BA47 ROI (F(1,23)=6.90, p = .015),
but not in the left BA 47 ROI (F(1,23)=.13, p=.73). This differential
effect of truth-value in the right BA 47 ROI for the two sentence types
was of a quantitative nature rather than a qualitative: the effect of
truth-value was statistically signicant for each sentence type, but it
was stronger in counterfactual sentences (F(1,23) =6.83, p b .001)
than in real-world sentences (F(1,23) = 2.21, p = .037). This differ-
ence was driven mainly by a large response to counterfactual false
sentences, which was larger than the response to real-world false
sentences (F(1,23)=3.59, p= .002), while the responses to counter-
factual true and real-world true sentences did not differ (F(1,23)=
1.06, p=.31).
Whole-brain analysis
The whole-brain analysis did not reveal any signicant clusters for
the interaction between Context and Propositional truth-value. How-
ever, because the ROI analyses revealed differential effects of truth-
value in counterfactual and real-world sentences, the following linear
contrasts (and their reverse counterparts) were further specied:
Counterfactual False > Counterfactual True, Real-world False>Real-
world True, Counterfactual>Real-world. Consistent with the absence
of a signicant Context by Propositional truth-value interaction effect,
the false minus true contrast elicited similar activation increases for
counterfactual and real-world sentences (see Table 3 and Fig. 2).
These clusters were located in left and right inferior frontal gyrus
(LIFG and RIFG, BA 45 and BA 47) extending into the middle frontal
gyrus (MFG, BA 8/9), left middle temporal gyrus (MTG, BA 21), medi-
al parts of the superior frontal gyrus (SFG, BA 6/8), and the left inferi-
or parietal lobule (IPL, BA 40). For real-world sentences an additional
cluster was located in the caudate nucleus. These results are a clear
replication of effects of world-knowledge violations as reported by
Hagoort and colleagues (Groen et al., 2010; Hagoort et al., 2004;
Menenti et al., 2009; Tesink et al., 2009, 2011).
Finally, the reverse contrast yielded no clusters that showed more
activity to true sentences than to false sentences. However, there was
a main effect of Context: counterfactual sentences overall elicited
more activity than real-world sentences in the left and right middle
temporal gyrus, a nding that is consistent with the results of
Menenti et al. (2009), who reported more activation in this region
for counterfactual context compared to real-world context. Consis-
tent with the main effect of context, the contrast (Counterfactual Fal-
se>Real-world False) elicited a signicant cluster in LMTG (k =440,
peak voxel coordinates [ 48 32 4]), as did the contrast (Counter-
factual True>Real-world True) (k=1421, peak voxel coordinates
[ 50 24 14]). Consistent with the interaction effect observed
in the ROI analysis, the contrast (Counterfactual False > Real-world
False) elicited a signicant cluster in RIFG (k=837, peak voxel coor-
dinates [36 282]), whereas the contrast (Counterfactual True > Real-
world True) did not.
Discussion
This fMRI study investigated the neural circuits that are sensitive
to the propositional truth-value of sentences about counterfactual
worlds or about the real world, and aimed to reveal hemispheric dif-
ferences between the inferior prefrontal gyri in processing counter-
factual truth-value and real-world truth-value. BOLD responses
were compared to critical words that rendered counterfactual or
3
2
1
0
3
2
1
0
Left Right
False - True
BA 45
False - True
BA 47
CF CFRW RW
CF
CF
RW RW
45
47
Fig. 1. (left graph) ROIs in the current study. Two 10-mm sphere centered at MNI coordinates [ 44 29 12] (BA 45, top) and [ 36 268] (BA 47, bottom) and their right hemisphere
equivalents. (right graph) Effect of propositional truth-value in counterfactual sentences (dark gray bars, CF) and real-world sentences (light gray bars, RW) in four ROIs (left/
right, BA 45/47). Displayed are the false-minus-true difference score (and 95% condence intervals) in average beta parameter value per sentence type and per ROI. (*pb .05).
3437M.S. Nieuwland / NeuroImage 59 (2012) 34333440

Citations
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Journal ArticleDOI
TL;DR: It is proposed that counterfactual thinking depends on an integrative network of systems for affective processing, mental simulation, and cognitive control that together enable adaptive behavior and goal-directed decision making and make recommendations for the study ofcounterfactual inference in health, aging, and disease.
Abstract: Counterfactual reasoning is a hallmark of human thought, enabling the capacity to shift from perceiving the immediate environment to an alternative, imagined perspective. Mental representations of counterfactual possibilities (e.g., imagined past events or future outcomes not yet at hand) provide the basis for learning from past experience, enable planning and prediction, support creativity and insight, and give rise to emotions and social attributions (e.g., regret and blame). Yet remarkably little is known about the psychological and neural foundations of counterfactual reasoning. In this review, we survey recent findings from psychology and neuroscience indicating that counterfactual thought depends on an integrative network of systems for affective processing, mental simulation, and cognitive control. We review evidence to elucidate how these mechanisms are systematically altered through psychiatric illness and neurological disease. We propose that counterfactual thinking depends on the coordination of multiple information processing systems that together enable adaptive behavior and goal-directed decision making and make recommendations for the study of counterfactual inference in health, aging, and disease.

46 citations


Cites background from "Establishing propositional truth-va..."

  • ...That counterfactual reasoning is strongly constraint by prior knowledge explains the increased engagement of the lateral temporal lobe (Nieuwland, 2012; Urrutia et al., 2012; Van Hoeck et al., 2013, 2014)....

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  • ...…that supports core processes for mentally undoing the present state of affairs and imagining alternative realities ‘‘if only’’ different decisions were made or actions taken (e.g., Nieuwland, 2012; Urrutia et al., 2012; De Brigard et al., 2013; Kulakova et al., 2013; Van Hoeck et al., 2013, 2014)....

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  • ...We suggest that the hippocampus is more likely to be engaged during counterfactual thinking in situations requiring extensive arbitrary relational binding (Nieuwland, 2012; Urrutia et al., 2012; De Brigard et al., 2013; Kulakova et al., 2013; Van Hoeck et al., 2013, 2014)....

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  • ...…processing counterfactual information (e.g., Coricelli et al., 2005, 2007; Chua et al., 2009; Fujiwara et al., 2009; Van Hoeck et al., 2010, 2014; Nieuwland, 2012; Xue et al., 2012; De Brigard et al., 2013), but this representational role seems to be in service of executive, goal-directed…...

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Journal ArticleDOI
TL;DR: The results suggest that different brain mechanisms are involved in the simulation of personal and impersonal counterfactual thoughts, and that the extent to which regions associated with autobiographical memory are recruited during the Simulation of Counterfactuals involving others depends on the perceived similarity and familiarity with the simulated individuals.
Abstract: Previous research has shown that autobiographical episodic counterfactual thinking—i.e., mental simulations about alternative ways in which one's life experiences could have occurred—engages the brain's default network (DN). However, it remains unknown whether or not the DN is also engaged during impersonal counterfactual thoughts, specifically those involving other people or objects. The current study compares brain activity during counterfactual simulations involving the self, others and objects. In addition, counterfactual thoughts involving others were manipulated in terms of similarity and familiarity with the simulated characters. The results indicate greater involvement of DN during person-based (i.e., self and other) as opposed to object-based counterfactual simulations. However, the involvement of different regions of the DN during other-based counterfactual simulations was modulated by how close and/or similar the simulated character was perceived to be by the participant. Simulations involving unfamiliar characters preferentially recruited dorsomedial prefrontal cortex. Simulations involving unfamiliar similar characters, characters with whom participants identified personality traits, recruited lateral temporal gyrus. Finally, our results also revealed differential coupling of right hippocampus with lateral prefrontal and temporal cortex during counterfactual simulations involving familiar similar others, but with left transverse temporal gyrus and medial frontal and inferior temporal gyri during counterfactual simulations involving either oneself or unfamiliar dissimilar others. These results suggest that different brain mechanisms are involved in the simulation of personal and impersonal counterfactual thoughts, and that the extent to which regions associated with autobiographical memory are recruited during the simulation of counterfactuals involving others depends on the perceived similarity and familiarity with the simulated individuals.

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  • ...…of semantic evaluation of non-autobiographical hypothetical and counterfactual statements show relatively little involvement of DN regions (Nieuwland, 2012; Kulakova et al., 2013), further suggesting that object-based counterfactual simulations may primarily recruit processes outside the…...

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  • ...…simulation is sufficient to engage the DN. Reduced activation of DN regions during object- versus personbased counterfactual simulations is consistent with findings in sentence-comprehension tasks involving counterfactual statements, which tend to recruit processes outside of DN (Nieuwland, 2012)....

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TL;DR: It is suggested that the left inferior frontal gyrus (lIFG) plays a major role in the interplay between the evaluation and generation networks and that inhibiting this region’s activity may have an effect on “releasing” the generation neural network, resulting in greater originality.
Abstract: Human creative cognition is commonly described as a twofold cyclic process that involves an idea generation phase and an idea evaluation phase. Although the evaluation phase makes a crucial contribution to originality, its underlying mechanisms have not received sufficient research attention. Here, we suggest that the left inferior frontal gyrus (lIFG) plays a major role in the interplay between the evaluation and generation networks and that inhibiting this region's activity may have an effect on "releasing" the generation neural network, resulting in greater originality. To examine the neural networks that mediate the generation and evaluation of ideas, we conducted an fMRI experiment on a group of healthy human participants (Study 1), in which we compared an idea generation task to an idea evaluation task. We found that evaluating the originality of ideas is indeed associated with a relative increase in lIFG activation, as opposed to generating original ideas. We further showed that temporarily inhibiting the lIFG using continuous theta-burst stimulation (Study 2) results in less strict evaluation on the one hand and increased originality scores on the other. Our findings provide converging evidence from multiple methods to show that the lIFG participates in evaluating the originality of ideas.

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  • ...For example, the lIFG was found to be sensitive to false sentences (Nieuwland 2012), judgment of congruent vs. incongruent reasoning (Tsujii et al. 2011), planning novel articulations (McGettigan et al. 2013), semantic unification (Zhu et al. 2012), and ambiguous words (Hargreaves et al. 2011)....

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TL;DR: The results suggest that counterfactual reasoning is a more complex cognitive process than false belief reasoning, showing stronger activation of the dorsomedial, left dorsolateral PFC, cerebellum and left temporal cortex.
Abstract: Behavioral studies indicate that theory of mind and counterfactual reasoning are strongly related cognitive processes. In a neuroimaging study, we explored the common and distinct regions underlying these inference processes. We directly compared false belief reasoning (inferring an agent's false belief about an object's location or content) and counterfactual reasoning (inferring what the object's location or content would be if an agent had acted differently), both in contrast with a baseline condition of conditional reasoning (inferring what the true location or content of an object is). Results indicate that these three types of reasoning about social scenarios are supported by activations in the mentalizing network (left temporo-parietal junction and precuneus) and the executive control network (bilateral prefrontal cortex [PFC] and right inferior parietal lobule). In addition, representing a false belief or counterfactual state (both not directly observable in the external world) recruits additional activity in the executive control network (left dorsolateral PFC and parietal lobe). The results further suggest that counterfactual reasoning is a more complex cognitive process than false belief reasoning, showing stronger activation of the dorsomedial, left dorsolateral PFC, cerebellum and left temporal cortex.

31 citations


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  • ...Although this region is commonly engaged by different forms of mental simulations, studies indicate it is stronger engaged while simulating a new or possible event, in contrast to a factual event (e.g., Addis et al., 2007, 2009; De Brigard et al., 2013; Nieuwland, 2012; VanHoeck et al., 2013)....

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This paper investigated the role of the left inferior frontal gyrus for counterfactual reasoning about what is in fact false as if it were true.