Thematic reasoning and theory of mind. Accounting for social inference difficulties in schizophrenia

Evolutionary Psychology
human-nature.com/ep – 2005. 3: 1-19
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Original Article


Thematic reasoning and theory of mind. Accounting for social inference
difficulties in schizophrenia

Rhiannon Corcoran, Psychology Department, University of Manchester, Oxford Road, Manchester
M13 9PL, UK. Email: mbrxsrc3@fs1.fse.man.ac.uk. (Corresponding author)

Christopher D. Frith, Institute of Neurology, University College London, Wellcome Department of
Cognitive Neurology, 12 Queen Square, London, WC1N 3BG, UK. Email: c.frith@fil.ion.ucl.ac.uk.

Abstract:

Background: Corcoran (2000, 2001) has suggested that theory of mind judgements
can be arrived at using analogical reasoning skills and she has proposed that this is
the route that people with schizophrenia take when they make inferences about
others’ mental states. Recent work has demonstrated a robust relationship between
mental state inference and autobiographical memory, providing initial support for the
model. This study examines the model further by exploring the assertion that in
schizophrenia the ability to infer the mental states of others also depends upon
effective social reasoning in conditional contexts.
Method: 59 people with a DSM IV diagnosis of schizophrenia and 44 healthy
subjects performed four versions of the thematic selection task. The versions varied
according to the familiarity and social nature of the material they incorporated. The
same subjects also completed the Hinting Task, a measure of theory of mind and tests
of intellectual functioning and narrative recall.
Results: The schizophrenia and the normal control groups differed in their
performance on all of the measures except that of intellectual functioning.
Explorations within the schizophrenia group indicated that social reasoning was most
markedly affected in the patients with negative signs and in those with paranoid
delusions while for the hinting task, those with negative signs performed significantly
worse than those in remission but this difference seemed to be due to these patients’
poorer narrative memory. There was evidence in the schizophrenia data to support the
hypothesis of a relationship between theory of mind and social conditional reasoning.
Conclusion: This work provided further support for the idea that in patients with
schizophrenia at least, judgements about the mental states of others are achieved
using analogical reasoning.

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Conditional reasoning and theory of mind in schizophrenia
Keywords: schizophrenia, theory of mind, conditional reasoning, social contract
theory, analogical reasoning.

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Introduction

I. The social reasoning of people with schizophrenia

Many of the characteristic symptoms of schizophrenia reflect alterations in
how patients view themselves within their social spheres (Cutting and Murphy,
1990). Biases in reasoning have been reported in association with psychosis for many
years (e.g., Von Damarus, 1944; Williams, 1964). More recently, authors have
focussed on different types of social reasoning in schizophrenia. Kemp, Chua,
McKenna and David. (1997) for example have examined emotive and neutral
syllogistic reasoning. Bentall and colleagues have, for many years, examined
attributional style in people with paranoid delusions (See Bentall, Corcoran,
Kinderman, Blackwood and Howard, 2001 for a review of this work). Probabilistic
reasoning has been the focus of Garety and colleagues (e.g., Garety, Hemsley and
Wessely, 1991) while other authors have explored probabilistic reasoning biases in
people with delusions using salient social material (Dudley, John, Young, Over,
1997; Young and Bentall).

Of particular relevance to the study reported here is the research that
continues to accumulate on theory of mind problems in people with schizophrenia.
Theory of mind (Premack and Woodruff, 1978) is a term that is now widely used to
describe the understanding that our own and other’s behaviour is determined by
thoughts, beliefs and intentions. Typical empirical tests of this skill use vignettes and
require participants to infer what is in the mind of one of the characters in the story.
Commonly, an understanding of another’s false belief and acts of deception are tested
(see Frith and Corcoran, 1996 for example) but the ability to understand pragmatic
language where intentions are hidden is an effective way to explore this skill in adult
samples (see Corcoran, Mercer and Frith, 1995)

This work began with the publication of Frith’s (1992) neuropsychological
account of schizophrenia where he argued that difficulty understanding the mental
states of other people was central to the formation and maintenance of paranoid
delusions. An impairment of this skill was also proposed to underlie some negative
and positive behavioural signs. In a series of four studies, Corcoran and Frith
attempted to test this hypothesis (Corcoran, Mercer and Frith.,1995; Frith and
Corcoran, 1996; Corcoran and Frith, 1996; Corcoran, Cahill and Frith 1997). The
initial study in the series supported the hypothesis with the subsequent studies
replicating the findings using different paradigms.

Since the original studies, several independent groups have explored theory of
mind in schizophrenia and all of them have confirmed problems in this skill in some
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Conditional reasoning and theory of mind in schizophrenia
patients (e.g., Langdon et al. 1997; Sarfati et al.,1997; Doody et al., 1998; Pickup and
Frith, 2001, Randell, Corcoran, Day and Bentall, 2003, Greig, Bryson and Bell,
2004).

Corcoran (2000, 2001) has attempted to ‘unpack’ the cognitive components of
mental state inference in a way that makes sense of the differential performance seen
in people with schizophrenia according to their clinical features. She has proposed
that when people attempt to infer another’s mental state, they refer initially to
autobiographical memory to see if any remembered event can inform the ongoing
problem-solving. Any relevant retrieved recollection will form a base from which the
inference process will proceed. Reasoning processes will work upon this memory to
render a solution suitable to the current situation by considering the relevant
conditional or situational variables at play. In other words, this model of mental state
inference proposes that people infer other’s mental states by retrieving information
from episodic memory and reasoning in a conditional manner about the similarities
and differences between the memory and the current situation. The model, being an
attempt to account for socio-cognitive difficulties in schizophrenia, presents an
alternative way of ‘mentalizing’ that is quite different from the modular view of
theory of mind dominant in the cognitive neuroscience literature (Leslie, 1994; Frith
and Frith, 2003). It does however have some similarities to the simulation model of
theory of mind proposed by Harris (1992) which proposes that the appreciation of
another’s mental state is achieved by imagining oneself in the other’s situation.

In work that provides support for this ‘alternative’ model, Corcoran and Frith
(2003) found robust correlations between the strength of autobiographical memory
retrieval and theory of mind functioning in people with schizophrenia. This study
assessed theory of mind using tests of pragmatic language (the hinting task) and
stories incorporating false belief and deception. Furthermore, Corcoran (2003)
demonstrated a substantial correlation between hinting task performance and an
ambiguous sentence comprehension task that required inductive reasoning skills
(Corcoran, 2003). Clearly, the performance of people with and without theory of
mind difficulties upon a task that explores conditional reasoning within social and
non-social contexts and within contexts that are either familiar or unfamiliar will
challenge the model further. This challenge is the focus of the current study.

II. Reasoning in familiar or unfamiliar and social or non-social contexts - the
thematic selection task


The Wason Selection Task (Wason, 1966) is a card selection task in which the
ability of people to reason in a logical fashion is explored. In the original version of
this classic deductive reasoning task, the subject is told that each card within a set has
a letter on one side and a number on the other. Then the experimenter states that the
rule: “If a card has a vowel on one side (p) then it has an even number on the other
side (q)” should hold. The subject is then shown one side of 4 cards from the set. The
exposed sides show a vowel (card p), a consonant (card not p), an even number (card
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q) and an odd number (card not q). The subject is then asked to decide which of the 4
cards it would be sufficient to turn over to see if the rule does indeed hold. When the
rule is expressed as an ‘if…then…’ statement then the logical choice is always to turn
over the card with the vowel on it (card p) and the card with the odd number on it
(card not q). Using this original, abstract version of the test, Wason and Johnson-
Laird (1972) reported that only 10% or fewer subjects could solve the problem. Most
people selected the ‘p’ card correctly but then erroneously selected the ‘q’ card. This
choice reflects the confirmation bias (i.e. the tendency to try to confirm a rule rather
than disprove it). This is an extremely robust empirical finding in the normal
population that has lead to the conclusion that people are extremely poor deductive
reasoners.

However, empirical work conducted during the early 1970’s seemed to
demonstrate that people became more able to solve the selection task problem if it
was couched in a familiar context (Wason and Shapiro, 1971; Johnson-Laird,
Legrenzi and Legrenzi, 1972). While the task remained a deductive one (since no
information other than that which was incorporated into the task was actually needed
to solve the problem) the familiarity of the context meant that people could rely upon
knowledge gleaned from other sources (i.e. inductive reasoning) to solve the problem.
In other words, if subjects had any relevant prior knowledge they would use it,
resulting in a performance that was more proficient. This explanation of this ‘content’
or ‘thematic’ effect came to be known as the ‘availability hypothesis’ (Tversky and
Kahneman, 1973). It remained relatively unchallenged as an explanation of reasoning
facilitation (though it was manipulated and extended by Cox and Griggs (1982) and
Griggs (1983)) until the rise of the domain-specific reasoning theories of which one is
social contract theory (Cosmides, 1985, 1989). The proponents of social contract
theory suggest that ‘Darwinian algorithms’ have evolved enabling more efficient
reasoning in situations involving social contracts. For example, the ‘cheater detector’
algorithm enables us to detect the behaviour of others aimed at increasing their own
net benefit at the expense of our own. If a selection task content activates this, or
another specialized algorithm, then deductive reasoning will be facilitated.
The results offered in support of the domain-specific theories are compelling and
argue against a straight-forward availability hypothesis. For example, Cosmides
(1989) showed that, even when apparently unfamiliar contexts are used, reasoning is
still facilitated providing the cheater detector algorithm is invoked. The idea that
specialized modules or algorithms exist to help us reason within particular social
situations is akin to the notion that a ‘theory of mind’ module has evolved in the
human brain, a notion that has received support from imaging studies of this skill
(Frith and Frith, 2003; Gallagher an Frith, 2003).

However, it can be argued that the extension or reformulation of the
availability hypothesis offered by Griggs (1983) can adequately account for
Cosmides’s findings. According to Griggs’s formulation, the facilitated reasoning for
the so-called unfamiliar social contexts arises because we can bring to bear
experience that, though not equivalent, is analogous to the context of the thematic
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selection task problem. In other words, analogical reasoning, or current problem-
solving achieved using similar information derived from past experience (Sternberg,
1977), can account for the facilitation effects used to support domain-specific
theories. This account of facilitation for social reasoning where specialized modules
or algorithms are not evoked, is consistent with the model of theory of mind proposed
by Corcoran (2000, 2001) (outlined above).

The aim of this study was to determine whether a relationship exists between
theory of mind and social conditional reasoning in a sample of people with
schizophrenia some of who will show poor theory of mind performance.

Method

Subjects


Fifty-nine people with a DSM IV diagnosis of schizophrenia were included in
this study. The majority of these participants lived independently in the community or
in staffed hostels. All but three, were taking antipsychotic medication. Typically these
were depot or atypical neuroleptics. Most of the sample was male. Data was also
obtained from forty four normal subjects gathered from various sources. These two
samples were matched for sex ratio (Chi sq. = 0.87, 1df, ns), age (t(equal variances
not assumed) = -1.84, 93.4df, ns)and estimated IQ.(t(equal variances not assumed) =
1.19, 93.4 df, ns) The demographic details of the samples can be seen in Table One.


Table 1: Demographic Details of the two groups.
Schizophrenia Normal
Control
Number 59
44
Mean Age (sd)
40.5 (10.1)
40.0 (13.7)
M:F ratio
51:8
35:9
Mean duration illness(SD) 13.9 (10.5)
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The current symptoms of the schizophrenic sample were assessed prior to
testing using the Present State Examination (PSE version 9; Wing, Cooper and
Sartorius, 1974). Ten participants had prominent negative signs including blunted
affect, social withdrawal and poverty of speech. A further ten participants had formal
thought disorder without negative signs. Sixteen had paranoid delusions including
delusions of persecution, reference, misinterpretation and thoughts being read but no
negative signs or thought disorder. Eight described passivity delusions including
delusions of control, delusions of influence, thought insertion and thought withdrawal
in the absence of paranoid delusions or behavioural signs and fifteen were in
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Conditional reasoning and theory of mind in schizophrenia
remission and reported being well for at least the preceding two weeks.

The Tasks

All subjects performed the 4 tasks described below.

The Thematic Selection Task


Four thematic selection task items were used in the study. The items, the word
count and Flesch Reading Ease scores for the stories as well as the instructions given
can be seen in the Appendix to this paper. Performance was not time-limited.

(i) The non-social unfamiliar version (NSU) incorporated the conditional rule within
a story where it was necessary to check that the correct type of trees had been felled.

(ii) The non-social familiar version (NSF). Here the conditional rule is embedded
within a story where it was necessary to check that hot taps were fitted with red dots
on them.

(iii) The social unfamiliar version (SF). In this case the conditional rule is embedded
within a story where it is necessary to check whether young men are legitimately
joining a tribal dance

(iv) The social familiar version (SU). Here the conditional rule is embedded within a
story where it was necessary to check whether people are drinking under age.


Scores ranging from 0-2 were computed for social reasoning and non-social
reasoning comprising for each the familiar and the unfamiliar form. The amount of
facilitation afforded by social contexts for each participant was calculated by
subtracting the number of non-social versions correct from the number of social
versions correct (i.e., (SF+SU)-(NSF+NSU)). Similarly, the amount of facilitation
afforded by familiarity for each participant was calculated by subtracting the number
of unfamiliar versions correct from the number of familiar versions correct (i.e.
(SF+NSF) – (SU+NSU)).

The Hinting Task


This task, devised by Corcoran et al. (1995), is a simple theory of mind test
where the participant must infer the intention behind veiled speech acts. The hints
constitute the final speech act of a main character in each of ten very short vignettes.
After the stories are read out (stories are available for the participant to read through
as many times as necessary), the subject is asked what the character really meant by
what he/she said. If an inference is not made or, if an inappropriate conclusion is
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drawn, more is added to the story in the form of an even more obvious hint. The task
has a maximum score of 20 and normal adults tend to score close to ceiling. An item
taken from the hinting task is presented in the appendix to this paper.

The Quick Test (Ammons and Ammons, 1962)


This is a measure of word-to-picture matching designed to give an estimate of
the level of general functioning expressed as an IQ and based upon the Wechsler
Adult Intelligence Scale (Wechsler, 1955). The participant is asked to state for each
given word which of four pictures the word goes best with. As such it is a measure
that assesses word –knowledge as well as the more ‘fluid’ ability of contextual
analysis. The test is an appropriate measure of the kinds of general skill that might be
used when answering ToM tests. It is therefore a particularly well- suited measure of
general functioning for this study.

Immediate Narrative Recall


The Story Recall subtest from the Adult Memory and Information Processing
Battery (Coughlan and Hollows, 1985) was used to assess the ability to recall a short
prose passage immediately after hearing it. It is important to assess the potential
influence of this ability for two reasons. First, people with schizophrenia are reported
to have poor episodic memories. Second, the conditional reasoning task used here
loads significantly on narrative memory.

Results

1. Schizophrenia versus normal control comparisons


Table 2 provides information about the group performances on the single
reasoning task items. Table 3 gives summary scores on background cognitive tasks,
the hinting task, social reasoning, non-social reasoning and facilitation afforded by
social and familiar contexts for the groups.

The results of statistical tests indicated that differences existed on the
performance of the experimental tasks between the sample of people with
schizophrenia and the normal control sample. Highly significant group differences
were found to exist on performance of the hinting task and the narrative recall task
with the schizophrenia sample performing poorly compared to the normal controls.
(Hinting: t = 5.15, 65.65 df, p<0.0001; story recall: t = 12.81, 101df, p<0.0001). It is
clear from Table 2 that the normal control group and, to a lesser extent, the
schizophrenia group as a whole perform better on the social versions of the reasoning
task than on the non-social versions. Paired sample ‘t’ tests comparing the total score
for the social and non-social items confirmed this impression for both groups (normal
control t=5.37, 43 df, p<0.0001; schizophrenia t=3.09, 58 df, p<0.005).
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To explore the effect of group membership on performance on the thematic
selection task items while taking into account differing narrative memory ability, a
multivariate analyses of covariance was conducted. This was significant (Wilks’
Lambda F(4, 96) = 3.504, p,0.05). Univariate tests indicated a significant effect of
group on the number of the social items answered correctly (F(1,99) =
10.12,p<0.005) as well as the number of non-social items answered correctly (F(1,99)
= 7.35, p<0.01). However, no significant effect of group was observed on the extent
of facilitation afforded social reasoning (F(1,99) =0.69, ns) or familiar reasoning
(F(1,99) = 0.636, ns). In none of these analyses was performance on immediate story
recall found to be a significant covariate.


Table 2: Percentage of each group giving correct answers for each reasoning task
item.

Non-social
Non-social
Social
Social
unfamiliar
familiar
unfamiliar familiar
Normal control group
32
32
52
84
Schizophrenia group
5
10
13.5
27


Table 3: Summary of Task Performance by the 2 groups – means and (sds) (CRT =
conditional reasoning task).

Schizophrenia
Normal
Control
Estimated IQ
100.7 (10.6)
102.7 (5.8)
Immediate story recall *
13.3 (7.3)
31.5 (6.9)
Social CRT score**
0.41 (0.67)
1.36 (0.72)
Non-social
0.15 (0.41)
0.64 (0.75)
CRT score ***
Extent of Social facilitation
0.25 (0.63)
0.73 (0.90)
Extent of Familiar facilitation
0.19 (0.60)
0.33 (0.84)
Hinting Task *
14.86 (5.3)
18.56 (1.2)

* p<0.0001 **p<0.005 ***p<0.01

2. Exploring the effects of signs and symptoms in schizophrenia
(See Table 4)


As outlined earlier, the literature on theory of mind in schizophrenia suggests
that some patients have more problems with ToM than others and that this difference
may be related to the nature of the signs and symptoms present. In particular, ToM
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difficulties have been associated with negative signs, thought disorder and paranoia.
In order to determine whether symptom specific findings arose in this sample for
theory of mind and for social conditional reasoning, the schizophrenia group was
divided according to current prominence of signs and symptoms displayed and
analyses of variance explored differential effects on the conditional reasoning task
and the hinting task. With respect to the conditional reasoning task, one way
ANOVAs indicated that symptom subgroup differences existed for social conditional
reasoning performance (F(4,54)=3.16, p<0.05)but follow-up post hoc tests were not
able to establish where the paired-group differences lay. However, the descriptive
data indicated that the largest differences in performance existed between the
paranoid group and the group with non-persecutory delusions and this difference
approached significance (p=0.058, 2 tailed test). The group with prominent negative
features also displayed more markedly poor functioning than those with non-
persecutory delusions (p=0.084, 2 tailed test). By contrast no significant group
difference was evident for non-social conditional reasoning performance (F(4,54)=
0.37, ns). These analyses were followed-up by a univariate ANCOVA to examine if
the symptom subgroup differences in social reasoning survived correction for
differences in non-social reasoning, immediate story recall and estimated IQ between
the groups. This analysis demonstrated a significant effect of group (F = 2.89, 4df,
p<0.05) with estimated IQ (F= 4.23, p<0.05) and performance on non-social
reasoning (F=11.18, p<0.005) significant covariates. Again, post-hoc pair-wise
comparisons were not able to illustrate where the significant group differences
existed. However, the difference between the estimated marginal means of the
paranoid group and the group with non-persecutory delusions was the largest and
approached significance (p=0.08, 2 tailed test). The same approach was used to assess
the symptom subgroup differences that existed for the Hinting Task. The one way
analysis indicated a significant effect of subgroup on hinting task performance
(F(4,54) = 4.43, p<0.005). Post hoc Dunnett’s tests demonstrated that the significant
difference arose between the group with prominent negative features and those in
remission. However, when a univariate ANCOVA was conducted to take into account
differences in immediate story recall and any impact of IQ, group differences on
hinting task performance did not survive (F = 1.19, 4df, ns). Immediate narrative
recall performance had a significant impact on hinting task performance (F= 13.11,
p<0.005) but estimated IQ did not (F = 1.12, ns).

There were marked differences in the extent of facilitation afforded by social
contexts within the schizophrenia groups as can be seen by the pie charts displayed in
Figure 1 (overleaf). It is clear from these that the group of patients in remission as
well as the small group with non-persecutory delusions perform most similarly to the
normal control group.



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Figure 1: Extent of social facilitation
in each of the groups
Normal controls
No facilitation
Non-persecutory delusions
50% facilitation
100% facilitation
Remission
Thought disorder
Paranoid delusions
Negative signs





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Document Outline

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