ssentences: Insights into the nature of ‘truth’ in language
icola
Univer
MAC, V
, Italy
fMRI ª 2008 Elsevier Srl. All rights reserved.
philosophers, with Protagoras defending that ‘‘man is the
measure of all things’’ and Socrates criticizing his relativism.
In the last decades philosophers have mainly sided up with
Protagoras, emphasizing that truth cannot be objectively
defined, but rather is relative to the individual who claims it
(Blackburn, 2005).
either consider that there are qualitative differences in the
processing of true and false statements (i.e., true and false
statements involve different mechanisms or processes) or
consider that these processes are fundamentally the same
and only differ in quantitative terms (i.e., true and false
statements are similarly processed and only differ in terms of
* Corresponding author. Faculty of Psychology and Education, University of Lisbon, Lisbon, Portugal.
available at www.sciencedirect.com
.el
cortex 45 (2009) 759–768E-mail address: jfredmarq@fpce.ul.pt (J.F. Marques).1. Introduction
The inquiry on the nature of truth in language comprehension
has a long history that can be traced to the ancient Greek
In empirical terms this debate is related to the process of
online language comprehension, where the meaning of
a sentence is derived and its truth verified. In this context,
a similar opposition can be found between perspectives thatAction editor Gereon Fink
Published online 8 November 2008
Keywords:
Cognitive processes
Meaning
Semantic memory
Language
using event-related functional-Magnetic-Resonance-Imaging ( fMRI). We show that when
true and false concept-feature statements are controlled for relation strength/ambiguity,
their processing is associated to qualitatively different processes. Verifying true statements
activates the left inferior parietal cortex and the caudate nucleus, a neural correlate
compatible with an extended search and matching process for particular stored informa-
tion. In contrast, verifying false statements activates the fronto-polar cortex and is
compatible with a reasoning process of finding and evaluating a contradiction between the
sentence information and stored knowledge.J. Frederico Marques
a,
*, N
a
Faculty of Psychology and Education,
b
Department of Neuroscience and CER
c
CRESA, Vita-Salute University, Milan
d
National Neuroscience Institute, Italy
article info
Article history:
Received 4 January 2008
Reviewed 1 February 2008
Revised 11 April 2008
Accepted 9 July 20080010-9452/$ – see front matter ª 2008 Elsevi
doi:10.1016/j.cortex.2008.07.004Canessa
b,c,d
and Stefano Cappa
b,c,d
sity of Lisbon, Portugal
ita-Salute University and San Raffaele Scientific Institute, Milan, Italy
abstract
The inquiry on the nature of truth in language comprehension has a long history of
opposite perspectives. These perspectives either consider that there are qualitative
differences in the processing of true and false statements, or that these processes are
fundamentally the same and only differ in quantitative terms. The present study evaluated
the processing nature of true and false statements in terms of patterns of brain activitycomprehensionResearch report
Neural differences in the proce
journal homepage: wwwer Srl. All rights reservedsing of true and false
sevier.com/locate/cortex.

whether the sentence was true or false. True and false state-
cortex 45 (2009) 759–768760level of activation). The latter relativist position finds support
in behavioral studies showing that the time required to
process true and false statements depends on the strength of
the relation between the concept and the property that is
being evaluated (e.g., ‘‘the dog has four legs’’). More specifi-
cally, independently of their true/false status, the stronger the
relation between property and concept, the quicker the
answer in terms of reaction time (RT) (Hutchinson and Lock-
head, 1977; Rips et al., 1973).
The possibility of qualitative different processes for veri-
fying true and false sentences remains an open question. In
fact, in our daily lives the distinction between true and false
statements is usually more subtle and not reducible to ambi-
guity or relation strength. Moreover, this relation strength in
terms of subject–predicate can be controlled across true and
false sentences. This control can be achieved by using true
and false sentences where subject and predicate are seman-
tically related which results in no RT or small RT differences
between the two types of sentences (McCloskey and Glucks-
berg, 1979). What may happen in this situation? Would it be
possible then to find any qualitative distinction or marker of
true vs false sentences processing?
Some behavioral studies suggest that true and false infor-
mation are initially represented as true (Gilbert et al., 1990,
1993). Next, other studies suggest that deciding that a sen-
tence is true may just involve finding the sentence informa-
tion in memory, while deciding that it is false may involve
finding a contradiction between the sentence information and
stored knowledge (e.g., Collins and Quillian, 1969; Glass et al.,
1974). In the first case, the task may be similar to the recall or
recognition of a specific memory trace, while in the second
case it may require reasoning or problem-solving. However,
the discussion about this possibility has been long forgotten
amidst the decline of interest in semantic memory as related
to sentence verification tasks (Chang, 1986). Moreover, since
neither the qualitative or quantitative models completely
accounted for all the observed data, each was modified in
order to achieve this goal. The result was that in many
instances it became very difficult to tell the two views apart
from behavioral data (Murphy, 2004).
With the development of imaging techniques it is now
feasible to explore the neural correlates of language process-
ing and in this way evaluate alternative cognitive theories on
the basis of brain activation patterns (e.g., Cappa, 2006;
Umilta´, 2006; Vallar, 2006; but see Coltheart, 2006 for an
opposing view). The relativist position finds support in terms
of patterns of neural activity from a recent paper by Hagoort
et al. (2004). These authors have shown that true and false
sentences increase the activation of the same brain regions in
the left inferior frontal cortex (BAs 45 and 47) in comparison to
a low-level baseline. Moreover, the activation in these regions
was higher for false than for true sentences. This quantitative
difference may be interpreted in terms of false sentences
requiring extra processing, as they provide information that is
more ambiguous or uncertain as compared to true sentences.
In accord with this interpretation are also results showing
increased activation in BA 45 for sentences containing
ambiguous words relative to sentences with unambiguouswords (Rodd et al., 2005). On the other hand, different patterns
of brain activity have been recently reported by Harris et al.ments were equated in terms of concept–feature relation
strength and exactly the same concepts and features were
used across the two types of sentences. As such, similar to
McCloskey and Glucksberg (1979), we expect no significant RT
differences, or small RT differences, between the two types of
sentences. Furthermore, if processing true and false senten-
ces involves only a single process then we expect that the
difference between the two conditions will be apparent in
quantitative terms within the commonly activated regions.
Alternatively, if processing true and false sentences involves
qualitative processing differences instead of a single process,
we expect that these will be reflected in the activation of
incompletely overlapping brain activity patterns (Cappa,
2006).
2. Method
2.1. Participants
Twenty-one healthy right-handed (Oldfield, 1971) partici-
pants, native speakers of Italian (9 males, 12 females; mean
age¼ 26.09 years, SD¼ 1.89, range¼ 24–29) took part in the
study. All subjects had normal or corrected-to-normal visual
acuity. All reported no history of psychiatric or neurological
disorders, and no current use of any psychoactive medica-
tions. Participants gave informed written consent to the
experimental procedure, which was approved by the local
Ethics Committee.
2.2. Experimental design and materials
The experiment involved a single within-subjects design,
where statement status was true or false. Statements were
composed of concept–features pairs embedded in a simple
sentence: concept X has/is feature Y (e.g., ‘The bottle floats’).(2008) for true, false and undecidable statements from a wide
range of contents (e.g., geographical, mathematical, semantic
synonyms, autobiographical). True compared to false state-
ments activated the ventromedial frontal cortex, while the
reverse comparison engaged the left inferior frontal gyrus,
anterior insula, dorsal anterior cingulate and superior parietal
cortex. When the statement was undecidable (such as ‘‘you
had eggs for breakfast on Dec 8th, 1999’’), the contrast with
true and false statements showed an increased activity in the
anterior cingulate, and a deactivation of the caudate nucleus
(Harris et al., 2008). However, the study did not control for
sentence ambiguity and the fact that true statements were
verified more rapidly than false statements is certainly related
to this lack of control. Moreover, the study did not evaluate for
common activations or for differences within these common
activations and, as such, does not allow us to compare the two
alternative theories.
The present study examined the impact of true and false
sentences on brain activity with a feature verification task and
fMRI. Participants read simple sentences composed of
a concept–feature pair (e.g., ‘the plane lands’) and decidedConcepts regarded animals and objects, and features were
either visual form/surface or motor/action features in equal