Centre for Forensic Behavioural Science, Monash University, and the Victorian Institute of Forensic Mental Health, Melbourne, Australia
University of Manchester, UK
Centre for Forensic Behavioural Science, Monash University, and the Victorian Institute of Forensic Mental Health, Melbourne, Australia.
Correspondence: Rachael Fullam, Centre for Forensic Behavioural Science, School of Psychology, Psychiatry and Psychological Medicine, Monash University, Victorian Institute of Forensic Mental Health, Locked Bag 10, Fairfield VIC 3078, Australia. Email: rachael.fullam{at}forensicare.vic.gov.au
None. Funding detailed in Acknowledgements.
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There is relatively little existing information regarding the neural correlates of deception in individuals with psychopathic traits.
Aims
To investigate the relationship between neural responses during deception and psychopathic personality traits in a sample of male participants drawn from the normal population.
Method
Twenty-four male participants carried out a simple deception paradigm while undergoing functional magnetic resonance imaging. Psychopathic traits were assessed in the sample using the Psychopathic Personality Inventory (PPI).
Results
Mean response times were greater for the lie than truth condition. Lie responses resulted in enhanced activation of the ventrolateral prefrontal cortex. The PPI sub-scales, coldheartedness, fearlessness, Machiavellian egocentricity, social potency and stress immunity were found to be correlated with activation patterns in the brain circuitry implicated in both deception and related processes such as behavioural restraint and social cognition.
Conclusions
This is a novel technology that may prove useful in our understanding of some of the key components of the psychopathy construct in both clinical and non-clinical contexts.
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The aim of the present study was to use a simple fMRI deception paradigm devised by Spence et al4 to investigate the relationship between BOLD responses during deception and psychopathic personality traits measured using the PPI in a sample of male participants drawn from the normal population. Similar to Nunez et al,9 a lie was defined by the three basic features described by Coleman & Kay.22 That is, the intentional giving of a false response and awareness that the response is false rather than a mistake. We predicted that consistent with the findings of previous studies using the same paradigm,1,4 deceitful responding (relative to truthful responding) would be associated with increased BOLD responses in the ventrolateral prefrontal cortex, and increased response times for false responses indicating an interference effect. We further predicted that scores on the PPI sub-scales would be significantly associated with BOLD responses in brain areas previously implicated in the neural control of deception.
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Measurement of psychopathic personality traits
Psychopathic personality traits were assessed using the Psychopathic
Personality
Inventory.19 The
PPI is a 187-item self-report questionnaire with a total score and 8
sub-scales designed to measure psychopathic personality traits in a
dimensional manner.
These include:
Each item consists of a statement to which participants must indicate how accurately it applies to them using a 4-point scale ranging from 1 `false' to 4 `true'. The PPI has been shown to have good convergent and discriminant validity in both community and criminal samples.19,23–27 In particular, it shows good criterion related validity when compared with structured, collaboratively rated clinical assessments of psychopathy such as the PCL–R.18,24 The PPI scores for the sample are shown in Table 1. The mean total PPI score for the sample was lower than that reported by Lilienfeld et al (S. Lilienfeld, personal communication, 2008), for a large sample of substance misusing male prisoners (see online supplement for details). However, individuals in the present sample did show total scores at or above the criminal mean and the fearlessness, social potency, coldheartedness and stress immunity scores for the present sample were remarkably similar to those reported for the criminal population. Additional figures demonstrating the sample distribution of scores on each sub-scale can be found in the online Fig. DS1.
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Table 1 The Psychopathic Personality Inventory scores for the sample
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Deception paradigm
The deception task used in the present study was based on the task reported
by Spence et
al.4 Prior to
scanning, participants were asked to fill in a questionnaire determining if
they had performed 36 everyday acts during the current day (making the bed,
taken a tablet, etc). Once in the scanner, participants were asked to lie or
tell the truth about the performance of the 36 acts. In a standard ABAB block
design, each participant was required to lie about the performance of each act
once and tell the truth about the performance of each of the 36 acts once.
Each of the 12 blocks contained 6 acts and each act was displayed visually on
a screen for 5 s in the form `In the course of today have you... (made the
bed)'. Participants were required to make a motor response on a button box in
order to answer yes or no. They were instructed to lie or tell the truth
depending on which prompt appeared on the screen. In order to increase task
performance, participants were informed that an experimenter would be
monitoring their responses in order to detect whether they were lying.
Participants carried out a practice block prior to the main task. Response
accuracy was calculated by comparing responses made to the truth or lie prompt
during the task to the original response made in the 36-item questionnaire.
Response times (seconds) were recorded for each trial and average response
times during the truth and lie conditions were compared using a two-tailed
paired-sample t-test. In addition, response times and response
accuracy (relative to the original questionnaire items) were correlated with
PPI sub-scales using Spearman's correlations.
MRI image acquisition
Images were acquired using a Philips (Eindhoven, Holland) 1.5 T Gyroscan
ACS NT retrofitted with Powertrak 6000 gradients, operating at a software
level 6.1.2 T2*-weighted volumes were acquired using a
singleshot echo-planar imaging pulse sequence. Each volume comprised 40
contiguous axial slices, (response time (TR)/echo time (TE) 5000/40 ms,
64x64 data matrix, 3.5 mm thickness with an inplane resolution of
3x3 mm). The stimuli were rear projected onto a screen using a liquid
crystal display projection system. Task administration was coupled to image
acquisition using personal computer software and hardware linked to a response
button.
Analysis
Imaging data were analysed using Statistical Parametric Mapping (SPM5,
Friston, The Welcome Department of Cognitive Neurology, London, UK). Images
were corrected for motion and then realigned with the first scan serving as a
reference. The scans were then normalised into a standard stereotactic
space28 using
Montreal Neurological Institute templates. Images were finally smoothed with a
10 mm Gaussian filter to facilitate inter-individual averaging. After this
spatial preprocessing, at an individual level, a general linear model with a
delayed boxcar waveform was used to model BOLD signal changes during the task.
The individual images were then combined in a random effects analysis that
would allow inference to the general population using an independent samples
t-test to investigate the main effect of the task. The main effect
for the lie condition was the BOLD signal seen in the lie condition minus the
BOLD signal seen in the truth condition. The main effect for the truth
condition was the reverse subtraction.
The resulting statistical maps were thresholded at P<0.001
uncorrected with only cluster sizes of five or more contiguous voxels being
reported. As the inferior (frontopolar/orbitofrontal/ventrolateral
prefrontal), and superior frontal (dorsolateral/dorsomedial prefrontal) cortex
are the regions in which activations are most consistently reported across
different deception paradigms in the literature, we concentrated our primary
analysis solely on these areas. In order to control for type I errors we
applied small volume
corrections29 for
family-wise error at P
0.05 to these a priori regions of
interest. Areas of activation at the P<0.001 uncorrected level are
also reported when bilateral activations were seen.
In addition, we performed an exploratory analysis of signal in those areas less consistently identified by the past literature as active during deceptive responses; anterior cingulate, caudate, insula, thalamus, temporal lobes, temporal poles, posterior cingulate and precuneus. Again, in these regions we performed small volume corrections for family-wise error.
The association between BOLD responses during the lie condition and scores
on the PPI sub-scales was investigated using simple regression analysis.
During this analysis, for each a priori specified brain area of
interest that exhibited a significant voxel-based correlation, the BOLD signal
change observed during the lie condition was extracted from SPM and used in
Spearman's correlational analysis (SPSS version 14 for Windows) in order to
produce confirmatory r-values. As a further protection against type I
errors we have only reported results where the probability value of the
associated r-value exceeded P
0.001 for unilateral
activations and P
0.01 for bilateral activations.
Finally, in order to control for possible within-sample variation in age, we examined the correlation between age and BOLD responses during the deception condition. Age was found to be positively correlated with BOLD response in the temporal poles and insula and was therefore entered as a nuisance covariate in any analyses where significant BOLD responses were exhibited in these areas.
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Mean response times (seconds) were significantly slower during the lie condition compared with the truth condition (lie mean response time 2.66 s (s.d.=0.42), truth mean response time 2.56 s (s.d.=0.39); t=2.43, P=0.024).
There were no significant correlations between any of the other mean PPI sub-scales/factor scores and mean response accuracy or response time for the lie condition or truth condition.
Functional MRI data
Main effect of task
During the lie condition (relative to the truth condition) an increased
BOLD response was seen in the left ventrolateral prefrontal cortex (Brodmann
area (BA)47). An increased BOLD response at the P<0.001
uncorrected level was also seen in the right ventrolateral prefrontal cortex
(Table 2 and online Fig.
DS2).
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Table 2 Main effect of the deception task
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During the truth condition (relative to the lie condition) an increased BOLD response was seen bilaterally in the frontopolar area of the prefrontal cortex (BA10) extending into the medial superior frontal cortex (Table 2).
The results remained similar when the analysis was rerun excluding six participants who achieved less than 90% overall response accuracy for the task.
Relationship between the PPI sub-scales and BOLD response during the lie condition
The results of the correlational analysis are shown in
Table 3. During the lie
condition (relative to the truth), fearlessness scores were negatively
correlated with BOLD responses in the right orbitofrontal cortex
(Fig. 1). Coldheartedness
scores were negatively correlated with BOLD responses bilaterally in the
temporal poles (Fig. 2).
Machiavellian egocentricity scores were negatively correlated with BOLD
responses bilaterally in the caudate. Social potency scores were negatively
correlated with BOLD responses bilaterally in the right posterior cingulate.
Stress immunity scores were negatively correlated with BOLD response
bilaterally in the insula. These associations remained significant after
covarying for handedness and age (where appropriate).
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Table 3 The association between Psychopathic Personality Inventory (PPI)
sub-scale scores and blood oxygen level dependent (BOLD) responses in brain
areas of interest
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Fig. 1 The association between Psychopathic Personality Inventory (PPI)
fearlessness and blood oxygen level dependent response in the right
orbitofrontal cortex during deception.
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Fig. 2 The association between Psychopathic Personality Inventory (PPI)
coldheartedness and blood oxygen level dependent response in the temporal
poles during deception.
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There were no significant associations between BOLD responses during the lie condition in any of the brain areas of interest and the PPI total score or impulsive non-conformity, carefree non-planfullness and blame externalisation sub-scale scores.
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Behavioural data
Consistent with previous studies in this
field4,9
we found that the behavioural data indicated that mean response times were
significantly longer for the lie compared with the truth condition but there
was no effect of personality trait scores. It is possible that the relatively
small sample size may account for the lack of an observed association between
response time and personality traits. However, Nunez et
al9 also failed
to find an association between response times during lie responses and scores
on the PPI. We did find, however, that stress immunity, which reflects a lack
of anxiety, was positively correlated with response accuracy in the lie
condition. This would support the argument that interpersonal differences in
trait anxiety can mediate behavioural and physiological responses during
deception.30,31
This is an area that may warrant further investigation in imaging studies of
deception.
Main effect of task imaging data
Consistent with our hypothesis, we found that the lie condition (relative
to the truth condition) was associated with increased BOLD responses
bilaterally in the ventrolateral prefrontal cortex. This is a replication of
the finding reported by Spence et
al4 using the
same task in a smaller sample, and as such represents the first
between-laboratory replication of an fMRI deception finding (a research gap
recently highlighted by
Spence32). This
finding also supports previous studies using different deception paradigms
that have reported deception related BOLD responses in inferior frontal
areas.6,8,9,14
As the ventrolateral prefrontal cortex has been shown to be active during a
number of cognitive control
paradigms33–36
this finding also adds further weight to the argument that deception engages
executive prefrontal systems in order to achieve the production of a `lie' at
the same time as withholding the
truth.1,4
Similar to Spence et
al4 we did not
find any significant BOLD responses during deception in any of the other
frontal areas of interest. Given that previous studies in the
area4–13
have shown deception-related activity in the dorsolateral prefrontal cortex
and orbitofrontal cortex, it is possible that between-study deception paradigm
and sample size differences may account for the current lack of findings in
these areas.
We also found that the truth condition was associated with increased BOLD responses bilaterally in the frontopolar cortex. In a recent review of frontopolar function, Koechlin et al37 suggest that during decision-making tasks, lateral inferior frontal regions inhibit frontopolar regions in order to switch to and maintain a given response set. They also propose that frontopolar regions are able to store a previous response set in a back-up buffer in order to reinstate it following a reduction in top-down inhibition. In the present study, during the lie condition, the lateral inferior frontal cortex may have been exerting a strong inhibitory influence on the frontopolar regions in order to override the alternative truthful response set and switch to the deceitful set. In the truth condition, the frontopolar regions may have shown enhanced activation while accessing and returning to the use of the truthful response set. It is possible, therefore, that the underlying `task-switching' nature of the deception paradigm used in the current study may be largely responsible for the activations seen during the truth condition. The majority of published studies in this area do not specifically examine BOLD responses during the truthful condition; however, of those that do, few reported any areas of activation during truthful responding.1,8–10 Despite these negative findings, Langleben et al7 reported truth-related activations in the left medial frontal gyrus (BA46). The differences in findings may not only reflect inter-study differences in methodology, but also, in this case in particular, inter-laboratory differences in the ability to accurately image the frontopolar region without a large degree of airspace related signal drop out.
Relationship between personality factors and imaging findings
Psychopathy as a construct is generally considered to be characterised by
high levels of callous unemotional traits and these traits are believed to be
related to dysfunction in the limbic (amygdala) striatal prefrontal
circuitry.38 The
ability to measure key components of the psychopathy construct in less
pathological samples allows us to postulate on the potential neuropathology of
this disorder in clinical samples. The present study found evidence that BOLD
responses during deception in a number of brain areas of interest were
correlated with some, but not all, psychopathic personality trait scores.
Specifically focusing on the prefrontal cortex, we found inverse correlations
between fearlessness scores and BOLD responses in the right orbitofrontal
lobe. This suggests that those with low levels of fear and harm avoidance may
find it easier to lie and therefore do not activate the orbitofrontal cortex
which is a key neural structure implicated in behavioural inhibition in a
number of previous imaging
studies.33,39
Our own work on the neuropsychology of behavioural inhibition in samples of
offenders with antisocial personality disorder suggests that this clinical
group are significantly impaired on tasks probing orbitofrontal cortex
function compared with healthy
controls.40 Given
reports of increased white matter volume in some of the prefrontal subregions
implicated in deception-related neurocircuitry in those who lie, cheat and
manipulate
others,16,17
this is a brain area that warrants more detailed investigation.
In our exploratory analysis, we found that coldheartedness was inversely correlated with temporal pole BOLD responses. As the temporal pole has been found to be active during theory of mind tasks,41 our findings highlight the importance of looking at the role of callous unemotional traits and theory of mind/mentalising ability in tasks assessing the cognitive elements that may be involved in the deception and manipulation of others. Nunez et al9 found that coldheartedness assessed using the PPI was negatively correlated with BOLD responses in the posterior cingulate and precuneus cortices. In the present study, BOLD signal in the posterior cingulate was inversely associated with PPI social potency scores. Differences between studies may reflect the gender differences in the nature of the samples studied. Base rates of psychopathic traits are lower in female populations,42 and female populations exhibit lower scores on some (but not all) specific symptoms such as callousness/lack of empathy on the PCL–R,42 PPI stress immunity, PPI social potency and on a factor similar to PPI coldheartedness.43 In addition, there is some indication of a gender difference in the bio-behavioural correlates of psychopathy, with only male cohorts exhibiting a lack of physiological reactivity to aversive stimuli44 and stress.45
In this study we also found that lower stress immunity scores (i.e. more anxiety/stress) were associated with greater BOLD responses in the bilateral insula. As the insula has been shown to be involved in error processing during Go/No Go tasks,46 it is possible that stress immunity (which may relate to vigilance) may influence the function of the neural circuitry involved in the processing and monitoring of errors. Although at least some degree of anxiety is needed to engage error processing circuitry appropriately, it is possible that high levels may impair accuracy performance on behavioural tasks and moderate neural responses in imaging studies. Further studies are required to investigate the significance of both trait and state anxiety in deception-related brain activation patterns in those with antisocial and deceptive personality traits.
We found that higher Machiavellian egocentricity scores were associated with reduced BOLD responses in the bilateral caudate. Although there is a limited literature to compare the findings of the present study, decreased caudate activity appears to be associated with higher scores on the interpersonal (deceptive/superficial/grandiose) component of psychopathy,47 indicating that people with these and related personality traits, such as Machiavellian egocentricity, show reduced activation of caudate regions which are a key component of the subcortical straital network. A common finding across species and methodologies is the involvement of the striatum, the input structure of the basal ganglia, in a circuit responsible for mediating goal-directed behaviour.48 In functional imaging studies, the caudate has been shown to be involved in the inhibition of both motor and mental responses49–55 and appears to be specifically involved in the mediation of arousal.56
Overall, our findings fit with the previous literature suggesting that simple deception tasks activate prefrontal regions implicated in behavioural restraint and conflict monitoring and that lying results in greater activation than truthful responding. Our findings also tentatively suggest that specific personality traits may have a modulating effect on brain responses to deception tasks and that future studies examining brain activation during deception in offenders with and without psychopathic traits may be of value in understanding the neuropathology of psychopathy and antisocial personality disorder.
Limitations
Although the results of the present study are suggestive of an association
between psychopathic traits and the neural processes involved in deception,
there are a number of limitations that need to be taken into consideration.
The deception paradigm used is highly constrained and similar in terms of
cognitive demands to a Go/No Go test of behavioural inhibition. Recent imaging
studies of deception are utilising more complex ecologically valid paradigms.
For example, a recent study by Abe et
al13 has
demonstrated the involvement of the amygdala in a deception paradigm with a
social component and it is possible that this neural response may also show
some relationship with the callous/unemotional aspects of psychopathy. In
addition, the use of the PPI in the present study may have limited the
measurement of the core deceitful/manipulative components of psychopathy. The
majority of the PPI items focus on impulsive/antisocial or fearless/dominant
traits,26 a more
selective use of multiple measures of deception, such as those used by Yang
et
al,16,17
may have produced more specific neural correlates of a deceitful personality
type.
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This article has been cited by other articles:
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A. Ehjaz Psychopathic traits and studies of deception The British Journal of Psychiatry, September 1, 2009; 195(3): 270 - 270. [Full Text] [PDF] |
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