University of Toronto Personality and Individual Differences Article Summary This is one of the latest research work on personality and neuroscience. Your

University of Toronto Personality and Individual Differences Article Summary This is one of the latest research work on personality and neuroscience. Your assignment is to read and summarise the main findings and the limitations in this research. Personality and Individual Differences 103 (2016) 74–81
Contents lists available at ScienceDirect
Personality and Individual Differences
journal homepage: www.elsevier.com/locate/paid
Hans Eysenck’s interface between the brain and personality: Modern
evidence on the cognitive neuroscience of personality
Rachel L.C. Mitchell a,?, Veena Kumari b,c
a
b
c
Centre for Affective Disorders, Institute of Psychiatry Psychology & Neuroscience, King’s College London, London, UK
Department of Psychology, Institute of Psychiatry Psychology & Neuroscience, King’s College London, London, UK
NIHR Biomedical Research Centre for Mental Health, South London and Maudsley NHS Foundation Trust, London, UK
a r t i c l e
i n f o
Article history:
Received 12 January 2016
Accepted 1 April 2016
Keywords:
Personality traits
Neuroticism
Extraversion
Emotion perception
Cognition
a b s t r a c t
In this review, incorporating functional and structural MRI and DTI, with evidence gathered over the last 15 years,
we examine the neural underpinnings of extraversion and neuroticism, the two major personality dimensions in
Eysenck’s (1967) biological model of personality. We present clear evidence that, as proposed by Eysenck nearly
half-a-century ago, these traits relate meaningfully to the functioning and structure of various cortical and limbic
brain regions. Speci?cally, there is a robust relationship between neuroticism and the functioning of several emotion processing networks in the brain, particularly during exposure to negative stimuli. The brain regions showing this association include a number of cortical regions implicated in emotion regulation, depression and
anxiety, in addition to many sub-cortical/limbic regions. Currently, there are few studies directly assessing the relationship between extraversion and the cortical arousal system in the context of varying stimulations but data
available so far are remarkably consistent with Eysenck’s model. Future neuroimaging studies guided by relevant
personality and cognitive theories, and with suf?cient power to allow application of sophisticated analysis
methods (for example, machine learning) are now needed to improve our understanding of the biological
basis of individual differences and its application in the promotion of well-being and mental health.
© 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/).
1. Introduction
Well before the advent of modern human brain imaging, Hans
Eysenck, the visionary psychologist and the most in?uential personality
researcher in recent history, proposed a theory (Eysenck, 1967) that
went beyond description and measurement of personality and, for the
?rst time, provided the neurophysiological causes of personality. It
was unique in trying to explain extraversion and neuroticism, the two
major personality dimensions in Eysenck’s model (the third dimension,
psychoticism, added formally later in 1975), in terms of individual differences in the functioning of aspects of the central nervous system
(Eysenck, 1967). Here, we review neuroimaging evidence, gathered
mainly over the last 15 years, examining the association between extraversion and/or neuroticism and brain activation/connectivity patterns
elicited by a wide range of cognitive and affective tasks. We have included relevant functional magnetic resonance imaging (MRI), structural
MRI and diffusion tensor imaging (DTI) studies generated in the context
of Eysenck’s three-factor factor model as well as Costa and McCrae’s
?ve-factor personality model (Neuroticism, Extraversion, Openness to
? Corresponding author at: Centre for Affective Disorders, (PO Box 72), Department of
Psychological Medicine, Institute of Psychiatry Psychology & Neuroscience, King’s
College London, 16 De Crespigny Park, Denmark Hill, London SE5 8AF, UK.
E-mail address: Rachel.Mitchell@kcl.ac.uk (R.L.C. Mitchell).
Experience, Agreeableness & Conscientiousness). There is a reasonable
correspondence between the two models for extraversion and neuroticism (Costa & McCrae, 1995). We have also considered ?ndings relating
to the remaining three factors of the ?ve-factor model as well as those
relating to psychoticism, the third dimension in Eysenck’s revised
model (Eysenck & Eysenck, 1975), were examined within the same
study, for completeness.
2. fMRI evidence
2.1. Cognitive processing
Eysenck’s theory proposed that the extraversion–introversion dimension (extraversion = positive affectivity, marked by pronounced engagement with the external world and characterized by high sociability,
talkativeness, energy and assertiveness) is caused by variability in cortical
arousal (Eysenck, 1967). Those who score low for extraversion (introverts) have lower response thresholds and are consequently more cortically aroused than those who score high for extraversion (extraverts). It
further postulated an inverted U-shaped relation between cognitive performance and ‘level of arousal’, jointly determined by environmental
arousal potential (de?ned in terms of a range of environmental manipulations and task parameters) and subject arousability as re?ected in
http://dx.doi.org/10.1016/j.paid.2016.04.009
0191-8869/© 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
R.L.C. Mitchell, V. Kumari / Personality and Individual Differences 103 (2016) 74–81
extraversion. These postulates jointly predict that, at low environmental
arousal potential, extraverts’ performance would be lower than that of introverts’. As environmental arousal increases, performance of extraverts
should improve and they should catch up with introverts; and, at high
levels of environmental arousal, extraverts should out-perform introverts
with a decline in introverts’ performance, until it becomes so arousing as
to evoke transmarginal inhibition (TMI) (Eysenck, 1994; Gray, 1964).
With evocation of TMI, introverts may experience lower arousal increments than extraverts. There is considerable support for these predictions
from behavioral studies (Eysenck, 1981). Eysenck’s model further postulated that level of arousal, resulting from a combination of environmental
arousal and subject arousability, is mediated by activity in a ‘cortical
arousal system’, modulated by reticulo-thalamic-cortical pathways
(Eysenck, 1967, 1981). A circuit that seemingly corresponds to this cortical arousal system, including the dorsolateral prefrontal cortex (dlPFC)
and anterior cingulate regions, has been identi?ed in studies applying
fMRI to a wide range of cognitive tasks (Duncan & Owen, 2000). Importantly, ?ndings of an fMRI study (Kumari, ffytche, Williams, & Gray,
2004), the only one so far to test the predictions concerning extraversion
and cortical activity at different cognitive loads (or stimulation levels), are
remarkably consistent with Eysenck’s model. Speci?cally, this study
showed that the higher the extraversion score, the greater the change in
fMRI signal in the dlPFC and anterior cingulate from rest (through 1and 2-back) to the 3-back working memory load condition. Furthermore,
also consistent with Eysenck’s model, which treats neuroticism and
psychoticism dimensions as independent of extraversion, the relationship
between extraversion and dlPFC and anterior cingulate activity was not
found for neuroticism or psychoticism in Kumari et al.’s (2004) study.
Concerning neuroticism, Eysenck proposed that the neuroticismstability dimension (neuroticism = negative affectivity, marked by
emotional instability and low tolerance for stress or aversive stimuli,
and characterized by anxiety, fear, moodiness, worry, envy, frustration,
jealousy, and loneliness) is explained by differences in the level of
activity primarily in the limbic system (Eysenck, 1967). Perhaps not
surprisingly, most existing fMRI studies have examined the effects of
neuroticism in implicit or explicit affect processing, emotion regulation,
fear/anxiety stress induction paradigms (reviewed and discussed in
the next section) rather than with pure cognitive paradigms. A very
recent study, which examined the effects of personality using the ?vefactor model, found that decreased and increased effective connectivity
within the working memory network, activated by a 3-back working
memory task, were associated with high neuroticism and high conscientiousness, respectively (Dima, Friston, Stephan, & Frangou, 2015).
Although these ?ndings show a signi?cant effect of personality in
neuroplasticity, their interpretation is rather dif?cult because neuroticism and conscientiousness had opposite effects. The effects of conscientiousness, however, appear consistent with possible extraversion
effects, since conscientiousness correlates positively with extraversion
when assessed using the Eysenckian scales (Costa & McCrae, 1995).
Notably, extraversion itself, as in the ?ve-factor model, did not have
any in?uence in this study.
An important line of enquiry in relation to fMRI of neuroticism using
cognitive (and other) paradigms is indicated by experimental evidence
showing greater trial-to-trial variability in cognitive performance (particularly reaction time) of high neuroticism scorers, relative to low
neuroticism scorers (Robinson & Tamir, 2005). This behavioral effect
may re?ect task-irrelevant cognitions such as worries and preoccupations in neurotic individuals. Moment-to-moment brain signal variability is also known to be present in neuroimaging studies and has
important implications for fMRI activation and connectivity studies
(Garrett et al., 2013). Interestingly, moment-to-moment brain signal
variability correlates with less, rather than more, reaction time variability across various paradigms and samples (Garrett, Kovacevic, McIntosh,
& Grady, 2011; McIntosh, Kovacevic, & Itier, 2008; Misic, Mills, Taylor, &
McIntosh, 2010; Raja Beharelle, Kovacevic, McIntosh, & Levine, 2012).
Despite a highly likely in?uence of neuroticism in this phenomenon,
75
given its known association with reaction time variability, no published
study has yet examined the effect of neuroticism in moment-tomoment/trial-to-trial variability in brain activations.
2.2. Affect
One of the great challenges faced by the human mind is the need to
comprehend the content of other minds. Thus a rapidly increasing literature has sought to explore the psychological and neural mechanisms
behind “the mental operations that underlie social interactions, including perceiving, interpreting, and generating responses to the intentions,
dispositions, and behaviors of others” (Green et al., 2008), namely ‘social cognition’. One of the most fundamental means we have of making
these inferences is the emotion cues that other people display. However, individual differences associated with personality traits are a key in?uence on the way we perceive and respond to emotion cues (Britton,
Ho, Taylor, & Liberzon, 2007). Indeed, our personality, whether we
tend to be shy or outgoing, anxious or contented, has a major in?uence
on our lives and the way we interact with the world around us (Hamann
& Harenski, 2004). For example, highly neurotic individuals preferentially respond to negative emotion cues, and highly extravert individuals preferentially respond to positive emotion cues (Canli et al.,
2001). Personality has these effects because it comprises an integrated
pattern of thinking, feeling and behaving that varies between individuals but is relatively stable within individuals over time (Suslow et al.,
2010). These chronic affective styles associated with personality tune
the affective system to be more sensitive towards one class of cues
than to another (Cunningham, Arbuckle, Jahn, Mowrer, & Abduljalil,
2010; Fruhholz, Prinz, & Herrmann, 2010). Beyond their everyday
implications for understanding normal socio-cognitive behavior,
neuroticism and extraversion are of great importance as trait dimensions, because of the implications for individual vulnerability for
emotion-related psychopathologies such as anxiety and mood disorders
(Brandes & Bienvenu, 2006; Foster & MacQueen, 2008; Gale et al., 2011;
Keller, 2004; Klein, Kotov, & Bufferd, 2011; Wright, Kelsall, Sim, Clarke,
& Creamer, 2013).
Adoption of cognitive neuroscience techniques undoubtedly facilitates a clearer understanding of how personality in?uences the way
people react to emotion cues. It has even been said by some that neuroimaging might prove superior to behavioral or cognitive paradigms in
characterising the effects of personality dimensions on reactivity to
emotion cues (Harenski, Kim, & Hamann, 2009). The thinking here is
that whereas behavioral and cognitive indices represent the combined
effects of all brain activity components during a task, neuroimaging
can isolate speci?c aspects of neural reactivity as being in?uenced by
speci?c personality dimensions. Although some psychological determinants of individual variability in emotional reactivity have been determined at the behavioral level, research has only recently begun to
explore the brain mechanisms that might enable this individual variability (Canli et al., 2001). This is because most prior neuroimaging
studies have taken a group-based approach, in which the mechanism
that determines emotional reactivity is studied in a group of healthy
individuals not preselected for any speci?c criteria (Calder, Ewbank, &
Passamonti, 2011; Hamann & Canli, 2004). Here the effect of individual
differences on emotion perception at the neural level is frequently ignored or dismissed as statistical noise (Calder et al., 2011; Canli, 2004;
Hamann & Canli, 2004). Yet these individual differences can exhibit
remarkable stability within participants, suggesting that they are not
random ?uctuations, and that they relate to traits that are different
between, but consistent within, individuals (Canli, 2004). With a correlational approach, individual differences in neural reactivity do not
represent noise, rather they represent valuable signal that can reveal
much about aspects of brain function of fundamental value to the
study of social cognition (Canli & Amin, 2002; Hamann & Canli, 2004).
Since the trait of neuroticism involves enhanced processing of negative emotion cues (Canli et al., 2001), one way of establishing the
76
R.L.C. Mitchell, V. Kumari / Personality and Individual Differences 103 (2016) 74–81
in?uence of neuroticism on patterns of brain activity is to study the neural response to negative emotions (Haas, Constable, & Canli, 2008). In
the original study of neuroticism, extraversion and neural reactivity to
emotion cues, Canli et al. observed that neuroticism correlated positively with neural reactivity to negative scenes in the middle frontal and
temporal gyri, whilst extraversion correlated with reactivity to positive
scenes in the inferior, middle and superior frontal gyri, the cingulate, the
inferior and middle temporal gyri, the basal ganglia and amygdala
(Canli et al., 2001). These correlations were both robust; and in the expected direction, that is greater neural reactivity to positive emotion
cues was associated with high extraversion, whilst greater neural reactivity to negative emotion cues was associated with high neuroticism.
Since this original study, subsequent research has con?rmed and
extended these ?ndings in the visual modality, using symbols, faces or
scenes. Thus, neuroticism has been associated with activity in the
middle frontal gyrus (‘negative’ upsetting scenes) (Canli et al., 2001),
medial PFC (sad faces) (Haas et al., 2008), anterior cingulate (‘negative’
upsetting scenes) (Haas, Omura, Constable, & Canli, 2007), temporal
pole (sad faces) (Jimura, Konishi, & Miyashita, 2009), amygdala (‘negative’ upsetting scenes) (Cunningham et al., 2010; Harenski et al., 2009),
and the basal ganglia (‘negative’ non-smiling/sad emotion symbols)
(Bruhl, Viebke, Baumgartner, Kaffenberger, & Herwig, 2011), when
perceiving facial emotion cues.
Beyond passive viewing of visual emotion cues or forced-choice
labelling tasks, other research on personality and affective reactivity
has sought to actively direct participant’s view towards or away from
emotion cues, by manipulating their attention. In this line of research,
neuroticism has been shown to in?uence activity in brain regions such
as the caudate and supramarginal gyrus even before a negative emotion
cue is visible, that is through directing attention towards its mere anticipation (Bruhl et al., 2011), activation of the former having also been
demonstrated more broadly for the anticipation of emotional music
(Salimpoor, Benovoy, Larcher, Dagher, & Zatorre, 2011). Increasing the
evaluative attentional processing demands by introducing emotionrelated con?ict has demonstrated that in such circumstances, neuroticism is typically associated with increased amygdala activity (Fruhholz
et al., 2010), which makes sense given the role of the amygdala in
vigilance (Davis & Whalen, 2001), and the aforementioned association
of neuroticism with a predisposition towards negative emotion cues.
Indeed, according to Eysenck’s own biological theory of personality,
high levels of neuroticism were hypothesized to re?ect increased reactivity of the limbic system (of which the amygdala is part), which then
predisposes highly neurotic people to react strongly to emotionally
arousing experiences and take longer to return to pre-arousal states
(Eysenck, 1967, 1994). Elsewhere in the limbic system, neuroticism
has also been observed to associate with degree of activity in the medial
PFC in response to emotional arousal, the authors in this study suggesting that neuroticism in?uences emotional reactivity by enhancing
neural sensitivity to high levels of emotional arousal, predisposing highly neurotic individuals to react strongly to arousing experiences (Kehoe,
Toomey, Balsters, & Bokde, 2012). Some emotion-relevant brain regions
show increased or decreased activity in association with neuroticism
depending upon speci?c emotional response/processes involved. For
example, highly neurotic individuals show increased activity during
anticipation of painful stimulation (possibly re?ecting higher vigilance,
anticipatory anxiety and emotional over-arousal) and decreased activity during painful stimulation (possibly re?ecting emotional blunting,
avoidance/passive coping strategy, learned helplessness, etc.) in the
anterior cingulate, thalamus, parahippocampal gyrus and thalamus
regions (Coen et al., 2011; Kumari et al., 2007).
In the temporal domain, evidence has shown that higher degrees of
neuroticism are associated with a sustained haemodynamic response
across time in the medial PFC to negative stimuli, not just with an instantaneous response (Haas et al., 2008). Such a link might thereby create a mechanism whereby rumination over time could facilitate the
association of neuroticism with increased vulnerability for depression.
The importance of taking temporal dynamics into account when using
neuroimaging to study the in?uence of personality on affective reactivity is further underscored when distinguishing between initial reactivity
to an emotional stimulus, and subsequent recovery once an emotion cue
terminates or ceases to be relevant. Closer examination of the time
course of neural response in the amygdala in one study demonstrated
that whilst initial amygdala reactivity did not predict trait neuroticism,
slower amygdala recovery from negative images after their offset did
predict greater neuroticism (Schuyler et al., 2012). Because neuroticism
is associated with greater perseveration of emotional events (Robinson,
Wilkowski, Kirkeby, & Meier, 2006), this link between greater neuroticism and slower amygdala recovery might form …
Purchase answer to see full
attachment