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Puppet Master: Possible Influence of the Parasite Toxoplasma Gondii on Managers and Employees


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The article reviews recent literature on the effects of host manipulation by the parasite Toxoplasma gondii (prevalent in about a third of the world’s population) on perception, cognition, and behavior of humans, and on the changes in their physical appearance and personality characteristics. I argue that the mind-affecting parasite paradigm offers many research opportunities for management sciences, especially for organizational psychology and neuroscience. The article summarizes the parasite’s physiological mechanisms of affecting the host; highlights important behavioral effects of the infection in humans; and speculates on the possible impacts on skills and careers of employees and managers, organizational dynamics, intercultural management, and gender work roles. The conclusion shows limitations of the presented speculations and possible directions for future research on Toxoplasma’s effect on organizational dynamics.
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rAcademy of Management Perspectives
2017, Vol. 31, No. 1, 6381.
University of Economics in Prague and Jan Evangelista Purkyn ˇ
e University
The article reviews recent literature on the effects of host manipulation by the par-
asite Toxoplasma gondii (prevalent in about a third of the worlds population) on
perception, cognition, and behavior of humans, and on the changes in their physical
appearance and personality characteristics. I argue that the mind-affecting parasite
paradigm offers many research opportunities for management sciences, especially
for organizational psychology and neuroscience. The article summarizes the para-
sites physiological mechanisms of affecting the host; highlights important behav-
ioral effects of the infection in humans; and speculates on the possible impacts on
skills and careers of employees and managers, organizational dynamics, intercul-
tural management, and gender work roles. The conclusion shows limitations of the
presented speculations and possible directions for future research on Toxoplasmas
effect on organizational dynamics.
Toxoplasmosis is a disease caused by the uni-
cellular parasite Toxoplasma gondii. This infection
afflicts 30% to 40% of worldwide human pop-
ulation, and the prevalence of toxoplasmosis, un-
like most other pathogens, is high even in some
developed countries (Tenter, Heckeroth, & Weiss,
2000) (see Figure 1). The disease is clinically latent,
and infected people usually do not show any visible
symptoms, so most afflicted people are unaware of
their infection. Nevertheless, knowing the life cycle
and effects of the parasite is useful for organiza-
tional researchers and practicing managers, be-
cause Toxoplasma is able to covertly alter cognition
and personal characteristics of infected individ-
uals. It systematically changes their physical ap-
pearance, their health, and ultimately their ability
to perform at work (Flegr, 2013a, 2013b; Webster,
Kaushik, Bristow, & McConkey, 2013). The aim of
this paper is to show how toxoplasmosis might
influence the cognitive and personality characteristics
of employees and managers, and offer speculations
on the possible impacts of these changes on the
careers of the infected people and on organiza-
tional dynamics.
Toxoplasma affects behavior of infected humans
by manipulating the central nervous system (see
Figure 2), so it can serve as a source of natural case
studies of how and why the hypotheses of orga-
nizational neuroscience are useful in studying orga-
nizational processes and employeesand managers
decision-making. So far such specific studies have
not been conducted, although using the paradigm of
a mind-affecting parasite does not share the meth-
odological limitations for which organizational neu-
roscience is frequently criticized (Ashkanasy, Becker,
& Waldman, 2014; Butler, OBroin, Lee, & Senior,
2016; Cropanzano & Becker, 2013; Lindebaum &
Jordan, 2014).
Ashkanasy and colleagues (2014, pp. 909910)
pointed out four main issues of contention re-
garding the application of neuroscience to orga-
nizational behavior theory and practice: fear
of reductionism, that organizational neuroscience
seeks to reduce organizational behavior to activ-
ity in particular brain regions or even neurons;
I am very grateful to Jaroslav Flegr, Ludmila Hadincov´
Julie Nov´
a, Petr Koblovsk´
y, Daniel
y, Marek
Vranka, Academy of Management Perspectives editor
Phillip Phan and two anonymous reviewers, and partici-
pants at workshops at J. E. Purkynˇ
e University, the Uni-
versity of Economics in Prague, and Charles University for
their inspiring comments and helpful feedback. This re-
search received support from the grant V
SE IP300040.
Copyright of the Academy of Management, all rights reserved. Contents may not be copied, emailed, posted to a listserv, or otherwise transmitted without the copyright holders express
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legitimate concerns with limitations of the methods
and technologies that underlie neuroscience re-
search; [that] practical applications of neurosci-
ence may be inappropriate or meaningless, and the
potential for application to issues beyond individuals
(e.g., team-based phenomena) is nonexistent; and
that some applications of neuroscience ... have
all the characteristics of (yet) another manage-
ment fad.
I address each of these potential problems in
turn. First, the parasite affects the neural and hor-
monal systems directly, so its necessary to use
reductionist, mechanisticphysiological expla-
nations of perception, decision-making, and be-
havior in studying its impact on human behavioral
patterns. Nevertheless, the infected people remain
at their workplaces, in everyday situations instead
of artificial laboratory experiments. We can there-
fore apply predictions from the mechanistic/
physiological explanations to actual behavior of
employees in firms. As Toxoplasma alters primarily
cognitive and personality characteristics, affected
individualsrelationships with other people are
affected too. Second, the effects of infection are
connected to teamwork and organizational man-
agement, not just decisions and behavior of an in-
dividual as is typical for neuroscience laboratory
studies. Third, if the parasites influence is truly
genuine, in some cases more so than in others, then
knowledge of its impacts enriches organizational
behavioral theory and holds highly practical insights
for human resources management and organiza-
tional management in general. Finally, although
Toxoplasma infection generally affects people neg-
atively, under some circumstances it can also have
a positive impact (e.g., some Toxoplasma-positive
people have more pronounced extroversion, which
is a predictor of higher status in team contexts;
DesJardins, Srivastava, K ¨
ufner, & Back, 2015), and so
it could enable organizational scholars to observe the
Prevalence of Toxoplasmosis (Seroprevalence) Per Country in Percent of Population
There is no data for the countries that are not shaded in the map. The source of country-level statistics is Flegr and Dama (2014).
Toxoplasmosis is typically diagnosed by serological tests, which measure levels of antibodiesimmunoglobulin G (IgG) or immuno-
globulin M (IgM)in the blood of the tested people. Most of the seroprevalence data comes from women of childbearing age (the
seroprevalence is therefore adjusted to a standard age of 22 years). Nevertheless, the seroprevalence reported in the epidemiological
literature varies enormously (Chemoh et al., 2013), and in many countries it is now dramatically decreasing, possibly due to a shift in
hygiene habits
64 FebruaryAcademy of Management Perspectives
selection of Toxoplasma-infected individuals with
induced change of personality for specific organiza-
tional positions or roles.
Furthermore, due to a possibility that the parasite
affects the forms of human cultures and economic
institutions as well (Lafferty, 2006; Maseland, 2013),
the findings about the parasite could be also used in
the field of intercultural or international manage-
ment. (Toxoplasma, as this article will show, can
cause infected people to act impulsively, and toxo-
plasmosis is quite widespread in France, for exam-
ple.) Moreover, the findings can also be used in
general research on decision-making errors and
biases of managers.
While all these research propositions seem to be
long shots (and some of them are truly just specula-
tions, as I highlight later in the review), I believe that
in the area of organizational neuroscience it is true
that a study of latent toxoplasmosis ... has its best
years ahead(Flegr, 2013a, p. 161).
Yet methodological and ethical problems prevail
in this paradigm as well. First, its not possible to infect
humans in randomized experiments. Therefore, most
evidence of the influence of toxoplasmosis on human
personality and cognition is of a correlational nature,
and as we all know, correlation does not mean causa-
tion. Second, although the effects of toxoplasmosis
are not pathological, the latent infection is chronic
and typically incurable in people. The disease can
create a stigma in infected persons and lead to dis-
crimination against them.
With this as the backdrop, the article proceeds
as follows: I present some basic information on
the protozoan parasite Toxoplasma gondii and the
physiological mechanisms that affect its hosts. The
first part of this systematic review of the parasites
influence on humans is focused on changes in the
cognitive abilities of infected people and the possible
impacts of their impaired cognition on their jobs.
The second part of the review concerns permanent
changes in personality characteristics and traits (as
conceptualized by the five-factor model; Goldberg,
1990) or appearance that infected people may un-
dergo. I then speculate how toxoplasmosis may in-
fluence work performance and careers of infected
employees through these changes in personality
traits. This section is followed by a short speculation
on the possible influence of the parasite on cultures.
The conclusion shows the limitations of the pre-
sented inferences and possible future courses of
research on Toxoplasmas impact on organizational
The objective of Toxoplasma is to make its way
from its intermediate hosts (typically rodents, but
probably all warm-blooded animals) to its final
hostscats and other felines (members of the family
Felidae). Only in the digestive system of cats can the
parasite sexually reproduce and spread (through the
cats excrement). If an intermediate host is infected
by Toxoplasma, the parasite quickly reproduces
asexually and its oocytes settle in the hosts brain and
other tissues and begin altering the hosts behavior.
These manipulations are sometimes very specific
for example, infected rats are no longer afraid of cat
odor, but they dont lose fear of other predatory
species (Lamberton, Donnelly, & Webster, 2008).
Other manipulations are straightforward: The re-
action time of infected animals increases; vigilance
and motor activity deteriorate. Nonetheless, the
infected rats show further risky behavior (Webster,
2007). The chances of a cat catching an infected
rat increase drastically, which means that Toxo-
plasma reaches its final destination (where it sex-
ually reproduces) faster, and the cycle repeats. The
manipulation of hosts increases with the length of
the infection, indicating a causal influence of the
parasite on the changes in its intermediate hosts
AToxoplasma Tissue Cyst in the Brain of
a Chronically Infected Mouse
Width of the cyst is about 50 mm; small darker bodies around the
cyst are brain cells. During its life cycle, Toxoplasma gondii con-
verts into various stages with different morphology. There are
many Toxoplasma strains, but the majority in the United States
and Europe fall into three distinct lineages (Saeij, Boyle, &
Boothroyd, 2005). Printed by permission of Jaroslav Flegr.
2017 65Houdek
behavior. They could not be merely the side effects
of an acute infection, which would rather induce
a more pronounced behavioral change at the be-
ginning. It cannot be ruled out completely that the
manipulation by the parasite is a wide-ranging
consequence of a chronic diseasetissue destruc-
tion and the hosts immune system activity (Flegr,
2013a). Nevertheless, Webster, Lamberton, Donnelly,
and Torrey (2006) showed that anti-parasite med-
ications are efficient in preventing related be-
havioral alterations (moreover, medications used
to treat psychiatric diseases possess anti-parasitic
properties, too).
Any warm-blooded animal can be infected by
Toxoplasma, including humans. The infection is
most frequently contracted by consuming poorly
washed vegetables or fruits from places contami-
nated with feline excrement, coming into direct
contact with the excrement, or consuming insuffi-
ciently cooked meat of infected animals (e.g., pork,
lamb, or turkey). That may be the reason why
countries with a tradition of eating undercooked
meat have a higher prevalence of toxoplasmosis (as
do countries with more people working in agricul-
ture, poor hygienic standards, and cats as common
After a short acute stage that resembles the flu, the
infection quickly enters a latent stage characterized
by the permanent presence of the parasites cysts in
the muscles and central nervous system. The chronic
disease is seemingly asymptomatic in most people.
Serious health complications are rare and appear
primarily in prenatal infections (a congenital in-
fection can cause miscarriage or severe impairments
in the newborn) or in patients with weakened im-
munity from HIV/AIDS or immunosuppressants
(after organ transplantation).
Toxoplasma cannot recognize in which host it is
present, so its manipulation affects behavioral
patterns not only in rodents but also in its atypical
hosts, including humans (Webster et al., 2013). For
example, infected men rate the smell of cat urine as
more pleasant than uninfected individuals do (Flegr,
a, Hodn ´
y, & Vondrov´
a, 2011).
Physiological Mechanisms of Manipulations
Cysts containing Toxoplasma are distributed rela-
tively randomly across the brain (but see McConkey,
Martin, Bristow, & Webster, 2013); in rodents, cysts
are found especially in the olfactory bulbs, the amyg-
dala, the nucleus accumbens, the cerebral cortex, the
cerebellum, the medulla oblongata, the basal ganglia,
and the septohippocampal and perihippocampal
regions (Webster & McConkey, 2010). Cysts can
cause direct neurodegeneration (see similar effects
of cytomegalovirus; Novotn ´
a et al., 2005), but these
pathological processes alone are unlikely to be
responsible for the observed behavioral changes.
This is because important behavioral characteris-
tics are left intact, except for the observed specific
behavioral alterations.
The placement of the cysts in the olfactory bulbs
and in the amygdala is not surprising because the
change in the perception of cat odor is a common
manipulation of Toxoplasma, and because the
amygdala handles stimuli that cause fear. Similarly,
a strong candidate for the location of the parasite in
the brain of a host is the nucleus accumbens, which
has demonstrated a role in a range of behaviors re-
garding rewards, expectations, pleasure, and fear
(Cauda et al., 2011). However, any direct effect of
the parasite in the selected regions relies on the
premise that parasites can locate these regions and
then implement their manipulation with surgical
precisionwhich does not seem probable. The
handling mechanism is rather an indirect neuro-
transmitter modulation. Toxoplasma causes chem-
ical changes in its immediate surroundings and
thereby influences certain neurons playing a role in
the targetedbehavior. Thus, it can strengthen or
weaken certain neuronal pathways and make some
physiological and behavior effects more likely than
others (Webster & McConkey, 2010).
The parasite can change the concentration level of
the neurotransmitter dopamine in the brain by local
inflammation of certain neuronal areas. This was
observed physiologically in mice and indirectly in
humans. Infected people are characterized by re-
duced novelty seeking (Flegr et al., 2003; Skallov ´
Kodym, Frynta, & Flegr, 2006), which is a per sonality
trait significantly associated with the dopaminergic
system (Cloninger, Svrakic, & Przybeck, 1993).
Moreover, the genome of Toxoplasma also contains
genes for key enzymes of dopamine synthesis
(Gaskell, Smith, Pinney, Westhead, & McConkey,
2009). Because there is no simple explanation for
why Toxoplasma should have similar enzymes for
itself, it is expected that the parasite induces a release
of dopamine into hoststissues to manipulate them
(Prandovszky et al., 2011). Dopamine is involved in
behavior related to getting rewards and avoiding
loss, impulsivity, learning, novelty seeking, and risk
taking (Jocham, Klein, & Ullsperger, 2011; Pine,
Shiner, Seymour, & Dolan, 2010; Sharot, Shiner,
Brown, Fan, & Dolan, 2009). These characteristics
66 FebruaryAcademy of Management Perspectives
undoubtedly have effects in many aspects of organi-
zational life.
The impact of the infection could be significant
with regard to outbreaks of several neurological and
psychiatric diseases associated with a biased func-
tion of the dopaminergic system. For example, hav-
ing toxoplasmosis was found to increase the risk of
schizophrenia 2.7 times, which is approximately
equal to the increased risk of a cannabis user (Torrey,
Bartko, & Yolken, 2012). The influence of toxoplas-
mosis was even identified at the onset of personality
disorders, Parkinsons disease, Alzheimers disease,
obsessive-compulsive disorder, recurrent migraines,
autism, brain tumors, and even depression (for re-
views see Flegr, 2013a; Webster et al., 2013). The rate
of prevalence of toxoplasmosis is correlated with
countriessuicide rates (Ling, Lester, Mortensen,
Langenberg, & Postolache, 2011); women infected
with toxoplasmosis are twice as likely to commit or
attempt suicide than uninfected women (Pedersen,
Mortensen, Norgaard-Pedersen, & Postolache,
2012). This effect is concentrated closer to the
moment of infection (it doesnt intensify with the
duration of infection), so it appears to be an im-
mediate reaction rather than a cumulative impact
of latent disease.
Many of the above-mentioned psychiatric disor-
ders are associated with depressive states, showing
the possible effect of Toxoplasma on the metabolism
of serotonin. Serotonin is synthesized from trypto-
phan, an amino acid that is a basic nutrient for many
parasites, including Toxoplasma. Stemming from
this, depression thus could be caused by a fattening
parasite (Flegr, 2013a, but see also Healy, 2015). If it
is true that the Toxoplasma is involved in the onset of
depression, it may worsen infected employeeslife
satisfaction, and there is no doubt that employees
psychological well-being heavily influences their
work-related outcomes (Luthans & Youssef, 2007;
Youssef & Luthans, 2007).
Toxoplasmosis may also affect testosterone levels.
Toxoplasma-positive men have a higher concen-
tration of testosterone and Toxoplasma-positive
women have a lower concentration of testosterone
than Toxoplasma-free controls (Flegr, Lindov ´
a, &
Kodym, 2008). The opposite direction of the testos-
terone shifts can explain the observed gender spec-
ificity of behavioral and personal alterations in
Toxoplasma-positive participants (see more in the
following sections). These results could be caused
by the immunosuppressive nature of testosterone,
making men more likely to be infected. On the other
hand, a study (Lim, Kumar, Hari Dass, & Vyas, 2013)
showed that Toxoplasma infection enhances ex-
pression of genes involved in facilitating synthesis of
testosterone, resulting in greater testicular testoster-
one production in male rats. The same mechanism
could work also in humans.
How Do the Puppets Behave? Effects on Cognition
and Working Memory
A managers performance (as is most workers)is
undoubtedly related to his or her mental abilities
(Eggers & Kaplan, 2013; Teece, 2007). General cog-
nitive abilities largely predict both academic and
occupational levels attained and work perfor-
mance, and do so better than any other trait or dis-
position (Kuncel, Hezlett, & Ones, 2004; Schmidt &
Hunter, 2004). Its not surprising that a third to half
of CEOs attended an elite school, which placed
them in the top 1% of cognitive abilities (Wai &
Rindermann, 2015). Current research on cognitive
ability and performance in the workplace focuses
on finding out which emotional and cognitive
processessuch as bounded attention and perception,
memory, and problem solvingare active in manage-
rial and strategic decision making or which (un)suc-
cessful cognitive climatesare prevalent within
organizations (Baron, 2006; Foss & Lindenberg,
2013; Hodgkinson & Healey 2011; Houdek, 2016).
Although there arent many studies on the impact
of toxoplasmosis on job-related cognition, published
studies thoroughly confirm that even in humans,
toxoplasmosis generally impairs basic cognitive
functions (see Table 1 for a systematic review). The
infected humans arent in danger of being caught by
a cat, obviously, though their slower reactions can
cause death or injury. Studies have shown that
Toxoplasma-positive people are more likely to be
involved in traffic accidents and workplace acci-
dents (see Table 1), although the latter relationship
was demonstrated only in small subsamples of
workers from a low social class, so a generalization of
these findings remains questionable. The preferred
explanation of the results is that the negative impacts
of toxoplasmosis will mainly be manifested in al-
ready prone groups or situations and/or contexts
where the basal cognitive strength is weak. This ex-
planation stems from the finding that there is more
frequent and earlier manifestation of Alzheimers
disease in people with low cognitive reserves (Stern,
Just like mice, infected humans have slower re-
actions. In a simple double-blind experiment
cek, Gaˇ
a, Smith, Zv´
ara, & Flegr, 2001), the
2017 67Houdek
Studies on Toxoplasmas Influence on Human Cognitive Functions
Study Country
Type of study
[specific group]
positive/control) Methods Findings
Ferreira et al. (2013) Brazil Survey of hospital patients
[children 613 years old]
8/92 Scholastic performance test Infected subjects had lower results on
the mathematics subtest of the
scholastic performance test.
Flegr, Havl´
cek, Kodym,
y, & Smahel (2002)
Survey of subjects
involved in traffic
accidents (case-control)
146/446 Correlation between relative
risk of traffic accidents and
Toxoplasma infection
Infected subjects had increased risk of
traffic accidents.
Flegr, Klose, Novotn´
a, &
cek (2009)
Prospective cohort study
design [male draftees]
Of 3,890 subjects
29.7% were
Correlation between relative
risk of traffic accidents and
Toxoplasma infection
Infected subjects (but only RhD negative)
had increased risk of traffic
Flegr, Novotn´
a, Lindov´
a, &
cek (2008)
Behavioral study 58/278 Reaction time test
(psychomotor performance)
Infected subjects (but only women) had
lower psychomotor performance.
cek, Gaˇ
a, Smith,
ara, & Flegr (2001)
Double-blind behavioral
60/56 Reaction time test
(psychomotor performance)
Infected subjects had decreased
psychomotor performance.
Lanchava, Carlson,
a, Flegr, &
Nave (2015)
Behavioral study [women] 39/40 Financial decision-making
Infection was not associated with
financial decision making in
a et al. (2008) Czech
Behavioral study 1st study 41/73; Reaction time test
(psychomotor performance)
Infected subjects (but only RhD negative)
had decreased psychomotor
2nd study 151/288;
3rd study 95/220
a, &
Flegr (2014)
Double-blind behavioral
44/192 Test of acoustic prepulse
inhibition of simple
reaction times
Infected subjects had prolonged reaction
times to acoustic signals.
Beste, Getzmann,
Gajewski, Golka, &
Falkenstein (2014)
Germany Behavioral study
[seniors, 631]
36/36 Auditory distraction
Infected subjects had compromised
attentional allocation and
Gajewski, Falkenstein,
Hengstler, & Golka
Germany Double-blind behavioral
study [seniors, 651]
42/42 Battery of neuropsychological
Infected subjects had an impairment of
various aspects of memory.
Stock, Heintschel von
Heinegg, K¨
ohling, &
Beste (2014)
Germany Double-blind behavioral
18/18 Stopchange paradigm Infection was not associated with
cognitive control processes (infected
subjects were better at
these tasks).
Alvarado-Esquivel et al.
Mexico Cross-sectional survey
(convenience sampling)
71/143 Correlation between clinical
characteristics and
Infection was associated with memory
Liesenfeld, Estrada-
ınez, & Urbina-
Alvarez (2012)
Mexico Survey of subjects
involved in work
accidents (case-control)
Of 133 subjects
involved in
accidents, 12 were
Toxo-positive; of 266
control, 20 were
Correlation between relative
risk of work accidents and
Toxoplasma infection
Infected subjects (but only those with
low socioeconomic status) had an
increased risk of work
68 FebruaryAcademy of Management Perspectives
Study Country
Type of study
[specific group]
positive/control) Methods Findings
ırez et al.
Mexico Survey of subjects
involved in traffic
accidents (case-control)
Of 159 subjects
involved in
accidents, 54 were
Toxo-positive; of 164
control, 59 were
Correlation between relative
risk of traffic accidents and
Toxoplasma infection
Infected subjects had an increased risk of
traffic accidents.
Sugden et al. (2016)* New
birth-cohort study
236/601 Correlation between various
phenotypes and
Toxoplasma infection
Infection was not associated with poor
impulse control or neurocognitive
Guenter et al. (2012) Poland Behavioral study 26/44 Battery of neuropsychological
Infection was not associated with any
cognitive impairments.
Kocazeybek et al. (2009) Turkey Survey of subjects
involved in traffic
accidents (case-control)
Of 243 subjects
involved in
accidents, 130 were
Toxo-positive; of 200
control, 56 were
Correlation between relative
risk of traffic accidents and
Toxoplasma infection
Infected subjects had an increased risk of
traffic accidents.
Yereli, Balcio˘
glu, &
Ozbilgin (2006)
Turkey Survey of subjects
involved in traffic
accidents (case-control)
Of 185 subjects
involved in
accidents, 60 were
Toxo-positive; of 185
control, 16 were
Correlation between relative
risk of traffic accidents and
Toxoplasma infection
Infected subjects had an increased risk of
traffic accidents.
Gale, Brown, Erickson,
Berrett, & Hedges (2015)
USA Population-representative
Of 4,178 subjects,
19.1% were Toxo-
Battery of neuropsychological
Infected subjects (but only those with low
socioeconomic status and in certain
racial-ethnic groups) had various
impairments of cognitive functions.
Mendy, Vieira, Albatineh,
& Gasana (2015a)
USA Population-representative
study [children 1216
years old]
Of 1,755 subjects, 7.7%
were Toxo-positive
Battery of neuropsychological
Infection was associated with lower
reading skills and memory capacities.
Mendy, Vieira, Albatineh,
& Gasana (2015b)
USA Population-representative
study [seniors, 601]
Of 4,485 subjects, 41%
were Toxo-positive
Memory tests Infection was associated with lower
immediate memory.
Pearce, Kruszon-Moran, &
Jones (2014)
USA Population-representative
Of 4,234 subjects,
20.9% were Toxo-
Battery of neuropsychological
Infected subjects (but only those with low
socioeconomic status) had various
impairments of cognitive functions.
Note: The above-mentioned studies were selected through the Google Scholar and PubMed databases. Laboratory and field studies, case studies, and surveys estimating the
influence of toxoplasmosis on the cognition of otherwise healthy people were included. The databases were searched using the following keywords: human, Toxoplasma,
toxoplasmosis, cognition, cognitive, memory, attention, perception, reaction, and problem solving. Articlesfrom 1950 to May 2016 were included. The results comprised more than
14,000 references. After excluding unsuitable articles (reviews; conceptual papers; animal studies; in vivo studies; studies on psychiatric, neurological, and other diseases; cross-
country comparative studies; and unpublished studies, typically theses), 41 remained. Another 19 studies were excluded because they didnt relate directly to cognitive abilities;
they monitored the prevalence of toxoplasmosis in different professions and other groups, or they were duplicates referred to in Table 2. The number of Toxo-positive participants is
an estimate across different serological analyses (i.e., acute and latent infections).
*The study is presented in both systematic reviews.
2017 69Houdek
first of its kind, participants had to press a designated
key as quickly as possible after a certain shape
appeared on the screen. In the first minute of the
experiment, there was no difference in the reaction
times of infected and uninfected participants. After
the first minute, the infected people started getting
significantly slower, which suggests that Toxo-
plasma weakens long-term ability to concentrate.
Other studies have indicated that infected people are
more easily tired or not able to concentrate on longer-
lasting tasks (see Table 1).
Of these studies (see Table 1), 12 found a negative
influence of toxoplasmosis on various cognitive
functions, six found a negative influence only in
certain subgroups of subjects, and four found either
no effect or an opposite effect. However, most of
these studies are conducted in convenience samples
and test multiple variables and thus do bear a large
risk of false positives (Bettis, 2012; Simmons,
Nelson, & Simonsohn, 2011). (On the other hand,
as mentioned earlier, there exists some suspicion
that Toxoplasma increases testosterone levels and
thus stimulates competitiveness in men, so many
testsresults can be skewed away from identifying
negative influence of toxoplasmosis on cognition in
men, because infected men could work harder in the
competitive environment of an experiment.)
The results presented in this section show that
Toxoplasma-positive people have longer reaction
times, they are more easily distracted from th eir long-
term tasks, and their working memory is worse
(Table 1). Good working memory and ability to ex-
ercise cognitive control are of course crucial for pre-
dicting job performance on a number of measures
(Ackerman, Beier, & Boyle, 2005; Tang & Posner,
2009). The infection also appears to be linked with
recklessness (Lindov´
a, Pˇ
a, & Flegr, 2012). In
sum, it is expected that during prolonged tasks that
require concentration, infected people will achieve
worse outcomes than uninfected individuals.
Nevertheless, the correlative nature of the analyses
allows the interpretation that certain unfavorable
socioeconomic conditions are related to both low
cognitive abilities and a higher risk of being infected
with toxoplasmosis (such as eating unwashed vege-
tables or uncooked meat, living in the countryside,
etc.). The association between infection and cogni-
tive deficits is usually weaker or even disappears
when the covariates of age, socioeconomic status,
and gender are controlled for (Gale, Erickson,
Berrett, Brown, & Hedges, 2016). Cross-sectional
surveys, however, cannot exactly show whether
toxoplasmosis has a direct impact on cognition
(although there is strong evidence that the difference
in personality traits between infected subjects and
controls increases with time since the moment of in-
fection; see below). The relationship between cogni-
tion and toxoplasmosis is reversible and modulated
by many other factors: Low socioeconomic status can
lead to cognitive difficulties (Mullainathan & Shafir,
2013) and a higher risk of being infected with toxo-
plasmosis, or infection can lead to cognitive difficul-
ties and subsequent low social status.
Management research has shown that in organi-
zational practice, people with different personality
profiles hold different beliefs and react differently
to work challenges (George, 1992; Raja, Johns, &
Ntalianis, 2004). The first large meta-analysis (Barrick
& Mount, 1991), the results of which have been cor-
roborated by subsequent meta-analyses (Judge, Heller,
& Mount, 2002; Judge, Higgins, Thoresen, & Barrick,
1999), used a five-factor model (Goldberg, 1990),
which has a long influential history of explaining or-
ganizational behavior and will also be used below in
a demonstration of how toxoplasmosis may affect
the discussed personality traits in humans. Barrick
and Mounts (1991) study found that the trait of
conscientiousnessa persistent, planful, responsible,
and hardworking personalityconsistently positively
correlates with various indices of a workerspro-
ductivity (job proficiency, training proficiency, and
personnel data) across different professions. Further-
more, the trait of extroversiona sociable, gregarious,
assertive personality craving reward and status
influences productivity in positions with substantial
social interactions, such as managers and sales.
Extroversion and conscientiousness are also the
strongest predictors of leadership (Judge, Bono,
Ilies, & Gerhardt, 2002). The personality construct
openness to experiencecorrelates with perfor-
mance in training proficiency but not anywhere
else. On the other hand, other studies conclude that
openness to experience is strongly related to in-
novation and creativity of workers and with intrinsic
motivation not only at workplaces (George & Zhou,
2001; Shalley, Zhou, & Oldham, 2004).
Conversely, neuroticisma personality manifest-
ing emotional instability, anxiety, and lack of psy-
chological adjustmentcorrelates positively with
dissatisfaction at work, low productivity, and in-
ability to lead (Judge, Heller, & Mount, 2002; Judge,
Higgins, Thoresen, & Barrick, 1999).
70 FebruaryAcademy of Management Perspectives
Of the 15 studies listed in Table 2, 14 found some
influence of toxoplasmosis on various personality
traits; only one (large) study found no effect (again,
a number of studies bear a large risk of false posi-
tives). The personality characteristics of infected in-
dividuals change and the impact generally becomes
more severe the longer they are infected, so it is un-
likely that subjects with certain personality profiles
are more prone to Toxoplasma infection (neverthe-
less, without human infection experimentswhich
are clearly unethicalit is not possible to decide
whether a genuine causal relation exists between
Toxoplasma infection and personality and other
changes). However, there are disparities in the find-
ings, and toxoplasmosis generally explains only
a small part of the variability.
For example, Skallov´
a et al. (2005) found that
Toxoplasma-positive participants, both men and
women, had lower scores in the psychobiological
factor novelty seeking than Toxoplasma-free partic-
ipants, and that infected subjects had little or no need
for novel stimulation and preferred familiar places,
people, and situations; these results largely confirmed
results obtained by Flegr et al. (2003). Also, Toxoplasma-
positive subjects scored significantly lower on the
test of verbal intelligence than Toxoplasma-free
subjects (although this characteristic might be
explained by different backgrounds of infected and
uninfected individuals). As indicated above, lower
novelty seeking is expected to be associated with
an increased concentration of dopamine in the
brain tissue, a product of the increased synthesis of
dopamine due to Toxoplasma tissue cysts. These
studies also show that Toxoplasma-positive sub-
jects tend to be more organized and methodical and
prefer activities with strict rules and regulations. In
contrast, Lindov´
a et al. (2012) observed lower con-
scientiousness in Toxoplasma-infected subjects,
particularly in men. The relationship between the
pathogen and conscientiousness-related traits is
thus unclear.
Toxoplasma-infected male and female subjects
showed higher extroversion than Toxoplasma-free
subjects (Lindov´
a et al., 2012). Toxoplasma-infected
men tend to be suspicious and jealous, they break
the social rules more often, and they suffer from low
superego strength, but these results are not consis-
tent across studies (see Table 2). As personal qual-
ities significantly influence workplace relations,
leadership, and management skills as well as team-
work performance (Barrick, Stewart, Neubert, &
Mount, 1998; Bradley,Klotz, Postlethwaite, & Brown,
2013), one should expect that changes in personality
characteristics (or altered levels of them) may also be
reflected in corporate practice.
The exact effect of the infection on work perfor-
mance or career growth is difficult to predict because
it is demonstrated on many levels. Moreover, per-
sonality traits and individual skills are linked to their
respective organizational contexts, and their dis/
advantageousness may depend on situational con-
ditions, tasks, and team composition (further dis-
cussion of the topic would be out of the scope of this
article). For example, toxoplasmosis increases ex-
troversion (i.e., social dominance and sociability),
which would be particularly beneficial for sales-
people, managers, and team leaders, but it reduces
cognitive abilities and willingness to try new things.
As it has been proven that leadership skill correlates
with extroversion even more than with intelligence
(Judge, Bono, Ilies, & Gerhardt, 2002; Judge, Colbert,
& Ilies, 2004), the net impact of toxoplasmosis could
be positive for a manager or a leader. Because toxo-
plasmosis lowers conscientiousness, we can specu-
late that infected people would more frequently fail
at their tasks, so that their career dynamics would
look like a supernova, burning bright but perishing
young. Toxoplasma-infected managers can also re-
duce the work satisfaction and productivity of their
subordinates because of their negligence or lack of
a coherent managing system. Infected team members
can limit the performance of the whole team.
The unique questionnaire Toxo94, based on
a pilot study conducted by Flegr (2010), uncovered
even more specific differences between Toxoplasma-
positive and -negative individuals. For example, in-
fected men and women were more likely to agree
with the statements My instinctive (reflexive) be-
havior under imminent danger is rather slow and
passive. In a situation where most people get alarmed
and instinctively jump aside, I am slow to react,and
I believe that some people have the power to impose
their will on others under hypnosis or otherwise.
Toxoplasma-positive men also agreed more with
the statement When I am attacked, physically or
otherwise, or when I should fight for something
important, I stop fighting at that moment. It is not
a result of a rational decision not to fight, as in fact I
know that I should continue fighting and I would
like to do so, but my own subconscious betrays me
and I lose the will to fight back.
The cited statements have many complex mean-
ings; conclusions gained from these questionnaires
are therefore questionable from a psychometric point of
view. Despite that, I would speculate that Toxoplasma-
positive people may manifest paranoid notions about
2017 71Houdek
Studies on Toxoplasmas Influence on Human Personality Traits
Study Country Type of study
positive/control) Methods Findings
Flegr (2010) Czech
113/330; 68/242; 55/
136; 47/276
Unique questionnaire (Toxo94) Infected subjects expressed various
personality aberrations (see citations in
the main text).
Flegr & Havl´
sample of women
55/136 Cattells 16 Personality Factor
Infected women had higher intelligence,
lower guilt proneness, and possibly also
higher ergic tension.
Flegr & Hrd´
90/248 Cattells 16 Personality Factor
Toxoplasma-positive men had lower
superego strength and protension.
Flegr, Kodym, &
sample of women
230/0; 55/0 Cattells 16 Personality Factor
Affectothymia, surgence, high superego
strength, parmia, and protension were
correlated with the length of the infection.
Flegr, Preiss, &
Klose (2013)
Survey of military
154/337 N-70 and NEO-PI-R Questionnaire;
Wiener Matrizen-Test of intelligence
Infected subjects expressed lower levels of
potentially pathognomic factors,
measured with the N-70 questionnaire,
and neuroticism. Toxoplasma-infected
subjects expressed lower intelligence
score (while RhD-negative).
Flegr et al.
Survey of military
229/628 Cloningers Temperament and Character
Toxoplasma-positive subjects had lower
novelty seeking, impulsiveness,
extravagance, and disorderliness scores.
Infected subjects also had lower IQs.
Flegr, Zitkov´
Kodym, &
Frynta (1996)
103/291 Cattells 16 Personality Factor
Infection in men was positively correlated
with low superego strength, protension,
guilt proneness, and group dependency.
For women, the prevailing traits were
affectothymia, alaxia, and untroubled
adequacy and self-sufficiency.
a et al.
56/239 Experimental economic games Infected men were less cooperative and
infected women were more cooperative
compared to their uninfected
a et al.
49/214 Cattells 16 Personality Factor
Infected men scored significantly lower in
conscientiousness and self-control than
uninfected men; a trend in the opposite
direction was observed in women.
Infected men scored lower in warmth
than uninfected men, whereas there was
no difference in women.
a, &
Flegr (2012)
47/276 NEO-PI-R Questionnaire Toxoplasma-infected male and female
subjects had higher extroversion and
lower conscientiousness.
a et al.
Survey of military
Of 533 subjects, 25.0%
were Toxo-positive
Cloningers Temperament and Character
Inventory; Eysencks lie scale
Toxoplasma-positive subjects had lower
novelty-seeking scores.
72 FebruaryAcademy of Management Perspectives
Study Country Type of study
positive/control) Methods Findings
a et al.
Survey of blood
Of 290 subjects, 61.2%
were Toxo-positive
Cloningers Temperament and Character
Inventory; Eysencks lie scale
Toxoplasma-positive subjects had lower
novelty-seeking scores.
Cook et al.
Germany Survey of healthy
controls as a part
of a case-control
475/474 Questionnaire for Measuring Factors of
Aggression; Disinhibition subscale of
the Sensation Seeking Scale
Infection was associated with higher
reactive aggression scores among women
but not among men. Infection was also
associated with higher impulsive
sensation-seeking among younger men.
et al. (2013)
Iran Convenience
112/125 Cattells 16 Personality Factor
Infected women had higher apprehension,
privateness, and tension scores and lower
openness-to-change scores. Infected men
had higher vigilance and mistrust scores.
Sugden et al.
236/601 Correlation between various tests and
questionnaires and Toxoplasma
Infection was not associated with any
personality aberrations.
Note: The above-mentioned studies were selected through the Google Scholar and PubMed databases. Laboratory and field studies, case studies, and surveys estimating the
influence of toxoplasmosis on the personality traits of otherwise healthy people were included (studies estimating influence on psychiatric and mental diseases and personality
disorders were not targeted, as they are outside the scope of this paper). The databases were searched using the following keywords: human, Toxoplasma, toxoplasmosis,
personality, and traits. Articles from 1950 to May 2016 were included. The results comprised more than 12,000 references.After excluding unsuitable articles (reviews; conceptual
papers; animal studies; in vivo studies; studies on psychiatric, neurological, and other diseases; cross-country comparative studies; and unpublished studies, typically theses), 42
remained. Another 27 were excluded because they didnt relate directly to personality traits; they monitored the prevalence of toxoplasmosis in different professions and other
groups, or they were duplicates referred to in Table 1. The number of Toxo-positive participants is an estimate across different serological analyses (i.e. acute and latent infections).
*The study is presented in both systematic reviews.
2017 73Houdek
processes in organizations and consequently fall vic-
tim to an abusive supervisor (Chan & McAllister,
2014). As noted by De Vries and Miller (1986,p. 271):
[F]eelings of guilt, worthlessness, and inadequacy
are pervasive. Individuals downgrade themselves;
they are self-deprecating and feel inferior to others,
claiming a lack of ability and talent. They abdicate
responsibility. A sense of helplessness and hope-
lessness prevails. External sources for sustenance are
needed to combat insecurity.
Effects on Work Performance
In studying the impact of personality characteris-
tics on workplace behavior, leadership, and pro-
ductivity, organizational neuroscience can use the
quite specific influence of toxoplasmosis on the pro-
duction of the sex hormone testosterone. Its impacts
on personality characteristics (decision making and
behavior) and appearance are well documented
(Zitzmann & Nieschlag, 2001). Some studies have
found that Toxoplasma-positive men had higher
testosterone levels than non-infected men (Flegr,
a, & Kodym, 2008; Zghair, Al-Qadhi, &
Mahmood, 2015). Infected women,on theother hand,
had lower levels of the hormone (but see Shirbazou,
Abasian, and Meymand, 2011).
High levels of testosterone have been closely linked
to perceived social status (Eisenegger, Haushofer, &
Fehr, 2011). It plays a significant rolein willingness to
take risks, leadership, and entrepreneurship (Apicella
et al., 2008; Brañas-Garza & Rustichini, 2011; Garbarino,
Slonim, & Sydnor, 2011) and, based on other evidence,
also in impulse control, an increase in planning and
executive abilities (Dreber, Gerdes, Gr¨
ansmark, & Little,
2013), and willingness to engage in antisocial and/or
corrupt behavior (Bendahan, Zehnder, Pralong, &
Antonakis, 2015). High levels of testosterone are also
negatively related to the accuracy with which people
infer the thoughts and feelings of others (Ronay &
Carney, 2013).
Toxoplasma-positive men also appear more
masculine and dominant to women (Hodkov´
a, Skallov´
a, Lindov´
a, & Flegr, 2007). For
a person who wants to be a successful leader, it could
be more important to just appear authoritative and
convincing than to actually possess such personality
traits, because specific physical traits are robustly
associated with aggressive and self-interested behav-
ior (Haselhuhn, Wong, Ormiston, Inesi, & Galinsky,
2014; Spisak, Homan, Grabo, & Van Vugt, 2012).
Manipulative effects of Toxoplasma are related to an
increase in facial masculinity, and studies have
confirmed that managers who have more masculine
facial features indeed have higher salaries and work
for more successful companies (Rule & Ambady,
2008; Wong, Ormiston, & Haselhuhn, 2011).
In the case of testosterone, two contradictory ef-
fects of Toxoplasma on behavior make the final
impact difficult to predict. For example, better per-
formance (in the sense of higher profitability) for
a broker depends on his (only men were studied)
higher level of testosterone (Coates & Herbert, 2008),
which is boosted by Toxoplasma, but as the disease
also slows down reaction times, the real-life influ-
ence would be mixed. In summary, we can speculate
that Toxoplasma-positive people can achieve high
positions, but their performance may decline due to
a decrease in conscientiousness, increased neuroti-
cism, and possible health risks. Because of the dif-
ferent effect of toxoplasmosis on testosterone in men
(increased levels) and women (decreased levels), its
even possible that toxoplasmosis may be a partial
culprit in the inequality of men and women in
leading positions (see the next section for more in-
formation on toxoplasmosis and gender work roles).
I believe that toxoplasmosis offers an informative
variable in the psychological and neuroscientific
model of the effects of personality, cognitive traits,
and even physical appearance on human capital
and thus on organizational outcomes. It can help
improve identification methods in research on
the impact of personality characteristics on career
outcomes and on teamsand firmsinner workings
(Borghans, Duckworth, Heckman, & Ter Weel,
2008; Daly, Harmon, & Delaney, 2009; Heckman,
2011). If it is true that the parasite gradually and
significantly alters certain aspects of personality
characteristics by manipulating neural and hor-
monal systems of humans, it should be possible to
observe differences in decision making and actions
of infected employees and managers in the orga-
nizational environment compared to those not
These observations should be identifiable at the
firm, region, state, and country levels, as the preva-
lence of toxoplasmosis varies significantly between
and within countries. For example, in the United
States age-adjusted seroprevalence is higher in the
Northeast (29.2%) thanin the South (22.8%), Midwest
(20.5%), or West (17.5%) (Jones et al., 2001).
On a national level, a higher proportion of the
population infected with toxoplasmosis is associated
74 FebruaryAcademy of Management Perspectives
with stronger neuroticism (Lafferty, 2006). Lafferty
also showed associations between a prevalence of
toxoplasmosis and uncertainty avoidance and mas-
culine sex roles, but those results were not robust. It is
possible that cultural dimensions alter individual
personality through situational or educational con-
ditioning and/or experience and that an aggregate
national personality might be created through the
collective behavior of individuals with a specific
personality (Hofstede & McCrae, 2004). The same way
that infected individuals systematically show evi-
dence of certain personality characteristics, nations
where toxoplasmosis is more frequent demonstrate
these same tendencies as well. What are the charac-
teristics of nations with higher prevalence of toxo-
plasmosis? Lafferty concluded:
Individuals in populations that are masculinein the
sex-role cultural dimension reinforce traditional
gender work roles gender differentiation, and have
a higher focus on ego, ambition, money, material
possessions, self-achievement, and work than on re-
lationships, people, social support, and quality of
life. Individuals in populations that rate high in the
cultural dimension of uncertainty avoidance feel
threatened by uncertain or unknown situations,
leading to a rule oriented society geared to reduce
uncertainty. (2006, p. 2753; inner references omitted)
However, similar cross-country analyses suffer
from a strong endogeneity problem in the causality
direction and in operating variables (moreover, the
associations between personality shifts and Toxoplasma-
infected individuals differ between men and women).
Nevertheless, after carefully controlling for deter-
minants of the prevalence of toxoplasmosis in the
population, such as climate, urbanization, level of
sanitation, the consumption of meat, and religion (in
some countries religions promote vegetarianism and
toxoplasmosis is rare), the prevalence of Toxo-
plasma may be a suitable instrument for monitoring
the impact of cultural patterns on organizationsin-
ner workings, business practices, or economics in-
stitutions (Maseland, 2013), and it might help to
explain a huge variation in management practices
across organizations in different countries (Bloom,
Genakos, Sadun, & Van Reenen, 2012). As the
prevalence of toxoplasmosis is high even in some
developed countries (its prevalence is largely inde-
pendent from the economic well-being of nations), it
can be used to decrease the risk of misidentifying
the influence of other biological factors on economic,
cultural, or business variables (Bonds, Dobson, &
Keenan, 2012).
Research focusing on whether varying prevalence
of toxoplasmosis within a country can explain the
specifics of regional (business) cultures would be
methodologically purer and more useful. This data,
however, is currently lacking.
The cited literature suggests that Toxoplasma-
positive individuals have specific personality
differences compared with the non-infected pop-
ulation, and that such differences could be caused
by physiological manipulation by the parasite (al-
though in some cases there is still a probability that
people with certain personalities have a higher
likelihood of getting infected). Toxoplasma-positive
individuals have slower reaction times, they are
more easily distracted, and their working mem-
ory is worse. Toxoplasma may decrease an in-
dividuals life satisfaction. Infected people more
often believe that their instinctive behavior under
imminent danger is rather slow and passive, and
that some people have the power to impose their
will on others. They also believe that when they
are attacked, they stop fighting because their own
subconscious betrays them. Infected men have
higher levels of testosterone, and their physical
appearance is portrayed as more masculine and
dominant. Toxoplasma thus could offer a suitable
model for research on the influence of personality
traits and cognitive skills on individual work perfor-
mance and on organizational outcomes. At pres-
ent, however, there are no studies on the effects of
toxoplasmosis in the context of an organizational
Utilization of the Toxoplasma model in organiza-
tional neuroscience (or in organizational research in
general) certainly has several limitations. Even
though some impacts of the disease on physiological
mechanisms of dopamine, serotonin, and testoster-
one have been demonstrated (Flegr, 2013b), further
research on exactly which chemical and physiolog-
ical processes Toxoplasma uses to manipulate its
human victims is only at its beginning. For example,
manifestation of the disease depends on the RhD
blood group (Novotn´
a et al., 2008). A recent study
(Hari Dass & Vyas, 2014) found that Toxoplasma is
able to cause specific epigenetic changes in medial
amygdala circuits. Amygdala circuits are, inter alia,
responsible for the sexual behavior of animals; ap-
parently, cats are no longer perceived as a threat by
an infected rat, but instead become a sexually at-
tractive stimulus.
2017 75Houdek
Furthermore, Tan et al. (2015) showed that in-
fection with Toxoplasma increases the propensity of
infected rats to make more impulsive choices. Their
study concludes: T. gondii infection ... represents
a behavioural syndrome consisting of reduced innate
fear, increased sexual attractiveness and greater de-
lay aversion; all hallmarks of a carpe diemanimal
personality(Tan et al., 2015, p. 5). As of now there is
only one study that has tested the parasites impact
on sexual and/or mating behavior of humans (Flegr &
Kuba, 2016). Although this is just speculation, toxo-
plasmosis could influence the quality of relationships
between men and women in workplaces or the prev-
alence of sexual harassment in firms (as infected men
have higher testosterone levels and infected women
tend to exhibit more warmth).
It is not evident whether toxoplasmosis influences
other personality traits such as creativity, self-
ishness, honesty, personal integrity, and the dark
triad personality traits (narcissism, Machiavellian-
ism, and psychopathy). It can also be expected (as
many of the cited studies indicate) that with controls
on covariates such as personal background, de-
mographics, education, and training, the effects of
the parasite on personality are not that strong, espe-
cially not in the corporate environment. Also, the
reviewed literature presents contradictory findings,
some of which could be false positives due to pub-
lication bias. More replications of relevant studies
are necessary (see Byington and Felps, 2016, for
a more general review of the credibility crisis in
management sciences).
Research on the behavioral demonstration of the
impacts of toxoplasmosis also uses specific groups of
participants (usually students, seniors, pregnant
women, or soldiers), which makes it difficult to
generalize the findings to the general population or
specifically to the business world (although this
issue is common in neuroscientific research). Psy-
chological and cognitive tests are relatively context-
specific, and in most cases questionnaire-based with
an absence of real incentives or trade-offs. It is not
possible to predict how the proposed findings would
end up in the high-stakes multitasking environment
of firms.
Obviously, there are ethical problems as well
(Lindebaum, 2013). Toxoplasma-positive people
could be discriminated against when their infection
becomes known. Nevertheless, knowledge of ones
own infection should lead to higher awareness of
systematic biases and tendencies that are connected
to toxoplasmosis. Mindfulness training or cognitive
behavioral therapy sessions would be advisable for
some infected individuals. Conversely, if people
knew about their disease and outcomes connected
with it, it could make them adopt an infected
identity,and they might start rationalizing their
own mistakes, failures, and lapses (Dijksterhuis &
van Knippenberg, 1998; Vranka & Houdek, 2015).
Another open question is whether toxoplasmosis
should be treated as a preexisting condition in the
realm of legal matters (insurance, health, tort and
criminal law, etc.).
There are many other microorganisms that can
affect some aspects of the human mind and/or be-
havior (Kramer & Bressan, 2015). For instance, the
cytomegalovirus may alter the personality of in-
fected subjects (Novotn´
a et al., 2005), and gut bac-
teria may play a role in anxiety and depression
(Mayer, Knight, Mazmanian, Cryan, & Tillisch, 2014)
or in processing emotions and sensations (Tillisch
et al., 2013). There is even a (small) possibility that
the influenza virus could modify human social be-
havior before the onset of symptoms (Reiber et al.,
2010). Future studies should verify the robustness of
these observed effects and investigate their relevance
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Petr Houdek ( is a Ph.D. candidate
in business economics and management at the University of
Economics in Prague, Czech Republic; he is also a Ph.D.
candidate in theoretical an d evolutionary biology at Charles
University in Prague. He was appointed as an assistant
professor at the Faculty of Social and Economic Studies at J.
E. Purkynˇ
e University in ´
ınad Labem, Czech Republic.
His primary research interests include behavioral econom-
ics, social psychology, and management sciences.
2017 81Houdek
... Nevertheless, the findings suggest that the duration of infection exacerbates behavioral aberrations (Flegr, 2013). There is also significant publication bias in the field, as small studies use convenience samples and usually find positive results; however, large-scale and population studies using census data typically find small or no effects (Houdek, 2017a). The findings are often contradictory (Johnson & Koshy, 2020;Worth et al., 2013). ...
... As stated, the infection can amplify impulsivity and (in some cases) sensation-seeking, or risk-taking behaviors in humans. The predictions arise that it could be related to managerial, organizational (Houdek, 2017a(Houdek, , 2017b, or entrepreneurial roles (Johnson et al., 2018). Johnson et al. (2018) confirmed that toxoplasmosis infection is associated with a tendency to major in business-related fields among U.S. university students. ...
Full-text available
This perspective shows how neurodiversity can increase public organizations’ innovations and output quality. Studies from business and entrepreneurship fields are used to argue that public organizations may prosper if they recruit neurologically atypical individuals. Their unique thinking styles, coping strategies, and life experiences can lead to public services innovation. The management of public organizations through neurodiversity programs may gain competencies benefiting all employees. However, the promotion of neurodiversity cannot be achieved without demanding changes in organizational culture. The article also illustrates the benefits of neurodiversity using the example of a neurogenerative disease (toxoplasmosis).
... The apicomplexan parasite Toxoplasma gondii is one of the most successful pathogens of medical importance. It is estimated that one third of the human population is chronically infected with the parasite, and in some countries the seroprevalence can exceed 80% (Houdek, 2017). The success of their worldwide distribution is due in part to the multiple transmission mechanisms they have, which include the ingestion of undercooked meat containing cysts or contaminated water and vegetables containing oocysts (Dunay et al., 2018). ...
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Toxoplasma gondii is the causative agent of toxoplasmosis, a disease that affects warm-blooded animals and one third of the human population worldwide. Pregnant women who have never been exposed to the parasite constitute an important risk group, as infection during pregnancy often leads to congenital toxoplasmosis, the most severe form of the disease. Current therapy for toxoplasmosis is the same as it was 50 years ago and has little or no effect when vertical transmission occurs. Therefore, it is urgent to develop new strategies to prevent mother-to-fetus transmission. The implementation of experimental animal models of congenital toxoplasmosis that reproduces the transmission rates and clinical signs in humans opens an avenue of possibilities to interfere in the progression of the disease. In addition, knowing the parasite load in maternal and fetal tissues after infection, which may be related to organ abnormalities and disease outcome, is another important step in designing a promising intervention strategy. Therefore, we implemented here a murine model of congenital toxoplasmosis with outbred Swiss Webster mice infected intravenously with tachyzoites of the ME49 strain of T. gondii that mimics the frequency of transmission of the parasite, as well as important clinical signs of human congenital toxoplasmosis, such as macrocephaly, in addition to providing a highly sensitive quantitative real-time PCR assay to assess parasite load in mouse tissues. As the disease is not restricted to humans, also affecting several domestic animals, including companion animals and livestock, they can also benefit from the model presented in this study.
... Toxoplasma gondii, the parasitic protozoon of cats, infects about one-third of the human population in both developed and developing countries (Tenter et al., 2000). Infected humans express no specific symptoms of the life-long infection, however, they differ from non-infected subjects by a higher incidence of many diseases and disorders (Flegr & Escudero, 2016;Flegr, Klapilová, et al., 2014;Flegr, Prandota, et al., 2014) and also by specific changes in personality (Flegr, 2013;Khademvatan et al., 2013;Lindová et al., 2012) and behavior (Fekadu et al., 2010;Houdek, 2017). These behavioral differences are mostly considered to be products or by-products of the manipulative activity of Toxoplasma aimed to increase the chance of transmitting from the infected intermediate host, which can be any warm-blooded animal, to its definitive host, a cat (Webster, 2007). ...
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Humans infected by Toxoplasma gondii express no specific symptoms but manifest higher incidence of many diseases, disorders and differences in personality and behavior. The aim of this study was to compare the political beliefs and values of Toxoplasma-infected and Toxoplasma-free participants. We measured beliefs and values of 2315 responders via an online survey (477 Toxoplasma-infected) using the Political Beliefs and Values Inventory (PI34). This study showed Toxoplasma-infected and Toxoplasma-free participants of our cross-sectional study differed in three of four factors of PI34, scoring higher in Tribalism and lower in Cultural liberalism and Anti-Authoritarianism. We found sex differences in political beliefs associated with Toxoplasma infection. Infected women scored higher in tribalism and lower in cultural liberalism, compared with the Toxoplasma-free control group, while infected men scored higher in economic equity. These results fit with sexual differences in behavior and attitude observed after toxoplasmosis infection. Controlling for the effect of worse physical health and mental health had little impact, suggesting that impaired health did not cause these changes. Rather than adaptation to prevalence of parasites, as suggested by parasite-stress theory, the differences might be side-effects of long-term mild inflammatory reaction. However, to get clear picture of the mild inflammation effects, more research focused on different infectious diseases is needed.
... Rather than causing sexual attraction to cat urine, however, Toxoplasma causes emboldened, sometimes reckless behavior due to an inhibited fear response. For example, Toxoplasma may influence the behavior of individuals in business and entrepreneurial settings (Houdek 2017). Researchers have found that college students infected with Toxoplasma are more likely to major in business, and in particular in "management and entrepreneurship" (Johnson et al. 2018). ...
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A parasite is an organism that lives in an intimate and durable relationship with its host and imposes a cost on that host, in terms of its ability to survive, grow, and/or reproduce. Despite the fact that more than 40% of animal species are parasites, parasitism is rarely discussed in introductory biology courses. This may be because parasites are often hidden within their hosts—and therefore easy to ignore. But parasites have important roles to play in ecosystems and we ignore them at our own peril. In this module, students have the opportunity to discover the hidden world of parasites: they will come face to face with living parasites, learn about what differentiates parasites from free-living species, observe some common adaptations to a parasitic lifestyle, explore the ecological role of parasites in food webs, and assess how parasite abundance might change in a changing world. To accomplish these goals, this module includes an introductory PowerPoint presentation (including a video of parasite ecologist Dr. Chelsea L. Wood delivering this introductory lecture) and two exercises. The first exercise is a wet lab that involves dissecting an easy (and disturbing) source of live parasite material: fresh fish from your local seafood market. The second exercise is a computer lab that will allow students to engage with real data to answer the question: how do human impacts on ecosystems change the abundance of parasites in wildlife? This module will introduce students to the basics of parasite ecology and provide an opportunity to practice their data analysis and interpretation skills.
... Rather than causing sexual attraction to cat urine, however, Toxoplasma causes emboldened, sometimes reckless behavior due to an inhibited fear response. For example, Toxoplasma may influence the behavior of individuals in business and entrepreneurial settings (Houdek 2017). Researchers have found that college students infected with Toxoplasma are more likely to major in business, and in particular in "management and entrepreneurship" (Johnson et al. 2018). ...
... The latter might explain the greater representation of people seropositive to T. gondii in accidents, including car accidents (Flegr et al. 2002;Gohardehi et al. 2018;Sutterland et al. 2019). There is increasing evidence of links between latent T. gondii infection and psychiatric diseases including depression, bipolar disorder, schizophrenia, behavioural disorders and poor cognitive function (Henriquez et al. 2009;Torrey et al. 2012;Pearce et al. 2014;Fuglewicz et al. 2017;Houdek 2017;Akaltun et al. 2019). Toxoplasma gondii infection is also correlated with higher rates of suicide (Ling et al. 2011;Pedersen et al. 2012;Sutterland et al. 2019). ...
Context. Cats are the definitive or primary host for pathogens that cause diseases in people and livestock. These cat-dependent diseases would not occur in Australia if cats had not been introduced, and their ongoing persistence depends on contacts with cats. Toxoplasma gondii is a protozoan parasite that cycles between cats and any other warm-blooded animals. People infected by T. gondii may appear asymptomatic, or have a mild illness, or experience severe, potentially lethal symptoms; the parasite may also affect behaviour and mental health. T. gondii is also a major contributor to spontaneous abortion in sheep and goats. Two species of Sarcocystis, another genus of protozoan parasite, cycle through cats and sheep, causing macroscopic cysts to form in sheep tissues that reduce meat saleability. Toxocara cati, the cat roundworm, causes minor illnesses in humans and livestock, and the bacterium Bartonella henselae causes cat scratch disease, an infection that can be contracted by people when scratched or bitten by cats carrying the pathogen. Aims. We estimated the economic costs of cat-dependent pathogens in Australia. Methods. We collated national and global data on infection rates, health and production consequences. Key results. We estimated the costs of two cat-dependent diseases (toxoplasmosis, cat scratch disease) in people at AU $6.06 billion (plausible range AU$2.11–10.7 billion) annually, and the costs to livestock production from toxoplasmosis and sarcocystosis at AU$11.7 million (plausible range AU$7.67–18.3 million). Most of the human health costs are due to the associations between T. gondii and higher rates of traffic accidents and mental illness in people. The causality behind these associations remains uncertain, so those costs may be overestimated. Conversely, our estimates are incomplete, infections and illness are under-reported or misdiagnosed, and our understanding of disease outcomes is still imperfect, all of which make our costs underestimated. Conclusions. Our analysis suggests that substantial benefits to public health and livestock production could be realised by reducing exposure to cats and breaking parasite transmission cycles. Implications. Reducing feral cat populations in farming and urban areas, reducing the pet cat population and increasing rates of pet cat containment could help reduce the burden of cat-dependent diseases to people and livestock.
... But that wasn't the reason reviewers gave for rejecting it: their broad conclusion was that the paper had nothing to do with marketing. We felt somewhat vindicated when a paper appeared in a prestigious management journal a short time later, calling the bug a "puppet master," and elucidating its effects on the behavior of both managers and employees (Houdek 2017). If this bug affects the behavior of managers and workers, then it is certain that it affects the behavior of consumers as well. ...
This paper is composed of scholarly essays that explore the problematic nature of marketing’s influence within the academy and organizations, potential explanations and causes, and how conceptual and theoretical research can address and move our discipline forward. Each section represents material and research developed through interactive sessions from Academy of Marketing Science conferences. Topics include the history of the marketing discipline, its innovation and loss of domain expertise; important internal and external environmental concepts that have impeded relevance and theoretical impact; foundational elements of how the discipline frames problems, provides methodological-based solutions, and influences the very subjects of our research in such a way as to lesson our contribution to scholarship and practice; and finally the discipline’s inability to understand the intangible nature of marketing activities and outcomes, as well as marketers’ struggle to articulate relevance in a way that is easily understood in the language of finance. Through this critical self-examination of the field of marketing a central premise emerged—a discipline-wide drift and myopic approach to rigor and relevance.
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Purpose The purpose of this study is to understand how neuroscientific tools are used and discussed in ongoing research on strategy in organizations. Design/methodology/approach The authors used a bibliometric study of bibliographic pairing to answer the research question. They collected data from the Web of Science and Scopus databases using the keywords “neuroscience*,” “neurostrategy*” and “neuroscientific*.” Findings This study presents a framework that relates fundamental aspects discussed in current research using neuroscientific tools: Neuroscience and its research tools in organizations; emotions and information processing; interdisciplinary application of neuroscientific tools; and moral and ethical influences in the leaders' decision-making process. Research limitations/implications The inclusion of neuroscientific tools in Strategic Management research is still under development. There are criticisms and challenges related to the limitations and potential to support future research. Practical implications Despite recognizing the potential of neuroscientific tools in the mind and brain relationship, this study suggests that at this stage, because of criticisms and challenges, they should be used as support and in addition to other traditional research techniques to assess constructs and mechanisms related to strategic decisions and choices in organizations. Social implications Neuroscientific methods in organizational studies can provide insights into individual reactions to ethical issues and raise challenging normative questions about the nature of moral responsibility, autonomy, intention and free will, offering multiple perspectives in the field of business ethics. Originality/value In addition to presenting the potential and challenges of using scientific tools in strategic management studies, this study helps create methodological paths for studies in strategic management.
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Humans infected by Toxoplasma gondii express no specific symptoms but manifest higher incidence of many diseases, disorders and differences in personality and behaviour. The aim of this study was to compare the political beliefs and values of Toxoplasma-infected and Toxoplasma-free participants. We measured beliefs and values of 2315 responders via an online survey (477 Toxoplasma-infected) using the Political Beliefs and Values Inventory (PI34). This study showed Toxoplasma-infected and Toxoplasma-free participants of our cross-sectional study differed in three of four factors of PI34, scoring higher in Tribalism and lower in Cultural liberalism and Anti-Authoritarianism. We found sex differences in political beliefs associated with Toxoplasma infection. Infected women scored higher in tribalism and lower in cultural liberalism, compared with the Toxoplasma-free control group, while infected men scored higher in economic equity. These results fit with sexual differences in behaviour and attitude observed after toxoplasmosis infection. Controlling for the effect of worse physical health and mental health had little impact, suggesting that impaired health did not cause these changes. Rather than adaptation to prevalence of parasites, as suggested by parasite-stress theory, the differences might be side-effects of long-term mild inflammatory re-action, although definitive conclusions cannot be reached due to lack of relevant literature.
Humans, wildlife, and domestic animals are intimately linked through shared infections. Many parasites and pathogens use multiple host species, either opportunistically or sequentially, such that managing disease risk frequently requires a broader understanding of the ecological community. The coccidian protozoan Toxoplasma gondii infects more than one hundred species of vertebrates, ranging from bats to beluga whales. In humans, acute toxoplasmosis can have serious health consequences for immunocompromised individuals. Even amongst asymptomatic patients, however, toxoplasmosis has been linked to a range of behavioral alterations and conditions, such as changes in risk tolerance, neuroticism, mental illness, suicide, and accident proneness. Whether such links are causal or simply correlational has been the subject of intense study and debate; from an evolutionary standpoint, selection may favor parasite-induced alterations in host behavior that increase the likelihood a host is consumed by the definitive host—in this case a domestic or wild felid. Here, we examine current evidence for parasite-induced manipulations of host behavior, in both humans and other animals. We critically evaluate proposed mechanisms through which infection might influence host behavior, which range from inflammation in the brain to changes in hormones or neurotransmitters. Considering estimates that T. gondii may infect up to one-third of the global human population, we conclude by examining the implications of these changes for human behavior, individual fitness, and emergent cultural properties. Expected final online publication date for the Annual Review of Animal Biosciences, Volume 9 is February 16, 2021. Please see for revised estimates.
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This article argues much academic misconduct can be explained as the result of social dilemmas occurring at two levels of Management science. First, the career benefits associated with engaging in Noncredible Research Practices (NCRPs) (e.g. data manipulation, fabricating results, data hoarding, undisclosed HARKing) result in many academics choosing self-interest over collective welfare. These perverse incentives derive from journal gatekeepers who are pressed into a similar social dilemma. Namely, an individual journal’s status (i.e. its “impact factor”) is likely to suffer from unilaterally implementing practices that help ensure the credibility of Management science claims (e.g. dedicating journal space to strict replications, crowd-sourcing replications, data submission requirements, in-house analysis checks, registered reports, Open Practice badges). Fortunately, research on social dilemmas and collective action offers solutions. For example, journal editors could pledge to publish a certain number of credibility boosting articles contingent on a proportion of their “peer” journals doing the same. Details for successful implementation of conditional pledges, other social dilemma solutions – including actions for Management academics who support changes in journal practices (e.g. reviewer boycotts / buycotts), and insights on credibility supportive journal practices from other fields are provided.
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This article develops a model of local thinking in managerial decision making. According to the concept, attention is drawn by selectively salient factors or recalls in specific decision-making contexts. Although decision makers are aware of the changing conditions, they do not make a sufficient mental correction for the fact that the relevance of these factors is not generalized. They overestimate the importance of an option that “easily comes to one’s mind”: They excessively extrapolate from their experiences and extreme news, succumb to reference points and imprinting. The usefulness of the concept of local thinking in explaining decisions taken by managers is demonstrated by a short conceptual review of several empirical studies on local economic and natural shocks, negotiation of bank loans, expert forecasts, workers’ compensations, and gender equality. The conclusion brings speculations about further implications of the theory for organizational research.
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Background: Toxoplasma gondii (T. gondii) is a protozoan parasite present in around a third of the human population. Infected individuals are commonly asymptomatic, though recent reports have suggested that infection might influence aspects of the host's behavior. In particular, Toxoplasma infection has been linked to schizophrenia, suicide attempt, differences in aspects of personality and poorer neurocognitive performance. However, these studies are often conducted in clinical samples or convenience samples. Methods/results: In a population-representative birth-cohort of individuals tested for presence of antibodies to T. gondii (N = 837) we investigated the association between infection and four facets of human behavior: neuropsychiatric disorder (schizophrenia and major depression), poor impulse control (suicidal behavior and criminality), personality, and neurocognitive performance. Suicide attempt was marginally more frequent among individuals with T. gondii seropositivity (p = .06). Seropositive individuals also performed worse on one out of 14 measures of neuropsychological function. Conclusion: On the whole, there was little evidence that T. gondii was related to increased risk of psychiatric disorder, poor impulse control, personality aberrations or neurocognitive impairment.
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The data includes measures collected for the two experiments reported in “False-Positive Psychology” [1] where listening to a randomly assigned song made people feel younger (Study 1) or actually be younger (Study 2). These data are useful because they illustrate inflations of false positive rates due to flexibility in data collection, analysis, and reporting of results. Data are useful for educational purposes.
This study adopted an interactional approach to understanding how 2 of the Five-Factor traits, openness to experience and conscientiousness, are related to creative behavior in the workplace. Openness to experience is theorized to result in high levels of creative behavior and conscientiousness is theorized to result in low levels of creative behavior when the situation allows for the manifestation of the trait influences. More specifically, the authors hypothesized that openness to experience would result in high levels of creative behavior if feedback valence were positive and job holders were presented with a heuristic task that allowed them to be creative. The authors also hypothesized that conscientiousness would result in low levels of creative behavior if supervisors engaged in close monitoring and coworkers were unsupportive. The authors tested their hypotheses in a sample of office workers, and 5 out of the 6 hypotheses were supported.
We revisit the psychological underpinnings of Teece's (2007) framework of dynamic capabilities development in the light of advances in social cognitive neuroscience and neuroeconomics. We argue that dynamic capabilities are based on a blend of effortful forms of analysis and the skilled utilization of less deliberative, intuitive processes, which enables firms to harness managers' cognitive and emotional capacities.
Behavioral patterns, including sexual behavioral patterns, are usually understood as biological adaptations increasing the fitness of their carriers. Many parasites, so-called manipulators, are known to induce changes in the behavior of their hosts to increase their own fitness. Such changes are also induced by a parasite of cats, Toxoplasma gondii. The most remarkable change is the fatal attraction phenomenon, the switch of infected mice’s and rat’s native fear of the smell of cats toward an attraction to this smell. The stimuli that activate fear-related circuits in healthy rodents start to also activate sex-related circuits in the infected animals. An analogy of the fatal attraction phenomenon has also been observed in infected humans. Therefore, we tried to test a hypothesis that sexual arousal by fear-, violence-, and danger-related stimuli occurs more frequently in Toxoplasma-infected subjects. A cross-sectional cohort study performed on 36,564 subjects (5,087 Toxoplasma free and 741 Toxoplasma infected) showed that infected and noninfected subjects differ in their sexual behavior, fantasies, and preferences when age, health, and the size of the place where they spent childhood were controlled (F(24, 3719) ¼ 2.800, p < .0001). In agreement with our a priori hypothesis, infected subjects are more often aroused by their own fear, danger, and sexual submission although they practice more conventional sexual activities than Toxoplasma-free subjects. We suggest that the later changes can be related to a decrease in the personality trait of novelty seeking in infected subjects, which is potentially a side effect of increased concentration of dopamine in their brain.