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rAcademy of Management Perspectives
2017, Vol. 31, No. 1, 63–81.
https://doi.org/10.5465/amp.2015.0163
ARTICLES
PUPPET MASTER: POSSIBLE INFLUENCE OF THE PARASITE
TOXOPLASMA GONDII ON MANAGERS AND EMPLOYEES
PETR HOUDEK
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 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 para-
site’s 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 Toxoplasma’s
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 employees’and 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, O’Broin, Lee, & Senior,
2016; Cropanzano & Becker, 2013; Lindebaum &
Jordan, 2014).
Ashkanasy and colleagues (2014, pp. 909–910)
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´
a,
Julie Nov´
akov´
a, Petr Koblovsk´
y, Daniel
ˇ
Sˇ
tastn´
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
ˇ
SE IP300040.
63
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 holder’s express
written permission. Users may print, download, or email articles for individual use only.
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 it’s necessary to use
reductionist, “mechanistic”physiological 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
individuals’relationships 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 parasite’s 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
FIGURE 1
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 antibodies—immunoglobulin 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, it’s 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 parasite’s
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 Toxoplasma’s impact on organizational
dynamics.
TOXOPLASMA GONDII, THE MASTER
The objective of Toxoplasma is to make its way
from its intermediate hosts (typically rodents, but
probably all warm-blooded animals) to its final
hosts—cats and other felines (members of the family
Felidae). Only in the digestive system of cats can the
parasite sexually reproduce and spread (through the
cat’s excrement). If an intermediate host is infected
by Toxoplasma, the parasite quickly reproduces
asexually and its oocytes settle in the host’s brain and
other tissues and begin altering the host’s behavior.
These manipulations are sometimes very specific—
for example, infected rats are no longer afraid of cat
odor, but they don’t 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 host’s
FIGURE 2
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 disease—tissue destruc-
tion and the host’s 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
pets).
After a short acute stage that resembles the flu, the
infection quickly enters a latent stage characterized
by the permanent presence of the parasite’s 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,
Lenochov´
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
precision—which 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 “targeted”behavior. 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 ´
a,
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 hosts’tissues 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, Parkinson’s disease, Alzheimer’s 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
countries’suicide 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 doesn’t 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 employees’life
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 manager’s 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). It’s 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
processes—such as bounded attention and perception,
memory, and problem solving—are active in manage-
rial and strategic decision making or which (un)suc-
cessful “cognitive climates”are prevalent within
organizations (Baron, 2006; Foss & Lindenberg,
2013; Hodgkinson & Healey 2011; Houdek, 2016).
Although there aren’t 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 aren’t 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 Alzheimer’s
disease in people with low cognitive reserves (Stern,
2009).
Just like mice, infected humans have slower re-
actions. In a simple double-blind experiment
(Havl´
ı
ˇ
cek, Gaˇ
sov´
a, Smith, Zv´
ara, & Flegr, 2001), the
2017 67Houdek
TABLE 1
Studies on Toxoplasma’s Influence on Human Cognitive Functions
Study Country
Type of study
[specific group]
N(Toxoplasma-
positive/control) Methods Findings
Ferreira et al. (2013) Brazil Survey of hospital patients
[children 6–13 years old]
8/92 Scholastic performance test Infected subjects had lower results on
the mathematics subtest of the
scholastic performance test.
Flegr, Havl´
ı
ˇ
cek, Kodym,
Mal´
y, & Smahel (2002)
Czech
Republic
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,
Berenreitterov´
a, &
Havl´
ı
ˇ
cek (2009)
Czech
Republic
Prospective cohort study
design [male draftees]
Of 3,890 subjects
29.7% were
Toxo-positive
Correlation between relative
risk of traffic accidents and
Toxoplasma infection
Infected subjects (but only RhD negative)
had increased risk of traffic
accidents.
Flegr, Novotn´
a, Lindov´
a, &
Havl´
ı
ˇ
cek (2008)
Czech
Republic
Behavioral study 58/278 Reaction time test
(psychomotor performance)
Infected subjects (but only women) had
lower psychomotor performance.
Havl´
ı
ˇ
cek, Gaˇ
sov´
a, Smith,
Zv´
ara, & Flegr (2001)
Czech
Republic
Double-blind behavioral
study
60/56 Reaction time test
(psychomotor performance)
Infected subjects had decreased
psychomotor performance.
Lanchava, Carlson,
ˇ
Seb´
ankov´
a, Flegr, &
Nave (2015)
Czech
Republic
Behavioral study [women] 39/40 Financial decision-making
experiment
Infection was not associated with
financial decision making in
females.
Novotn´
a et al. (2008) Czech
Republic
Behavioral study 1st study 41/73; Reaction time test
(psychomotor performance)
Infected subjects (but only RhD negative)
had decreased psychomotor
performance.
2nd study 151/288;
3rd study 95/220
Pˇ
r´
ıplatov´
a,
ˇ
Seb´
ankov´
a, &
Flegr (2014)
Czech
Republic
Double-blind behavioral
study
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
paradigm
Infected subjects had compromised
attentional allocation and
disengagement.
Gajewski, Falkenstein,
Hengstler, & Golka
(2014)
Germany Double-blind behavioral
study [seniors, 651]
42/42 Battery of neuropsychological
tests
Infected subjects had an impairment of
various aspects of memory.
Stock, Heintschel von
Heinegg, K¨
ohling, &
Beste (2014)
Germany Double-blind behavioral
study
18/18 Stop–change paradigm Infection was not associated with
cognitive control processes (infected
subjects were better at
these tasks).
Alvarado-Esquivel et al.
(2014)
Mexico Cross-sectional survey
(convenience sampling)
71/143 Correlation between clinical
characteristics and
Toxoplasma
infection
Infection was associated with memory
impairment.
Alvarado-Esquivel,
Torres-Castorena,
Liesenfeld, Estrada-
Mart´
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
Toxo-positive
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
accidents.
68 FebruaryAcademy of Management Perspectives
TABLE 1
(Continued)
Study Country
Type of study
[specific group]
N(Toxoplasma-
positive/control) Methods Findings
Galv´
an-Ram´
ırez et al.
(2013)
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
Toxo-positive
Correlation between relative
risk of traffic accidents and
Toxoplasma infection
Infected subjects had an increased risk of
traffic accidents.
Sugden et al. (2016)* New
Zealand
Population-representative
birth-cohort study
236/601 Correlation between various
phenotypes and
Toxoplasma infection
Infection was not associated with poor
impulse control or neurocognitive
impairment.
Guenter et al. (2012) Poland Behavioral study 26/44 Battery of neuropsychological
tests
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
Toxo-positive
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
Toxo-positive
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
study
Of 4,178 subjects,
19.1% were Toxo-
positive
Battery of neuropsychological
tests
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 12–16
years old]
Of 1,755 subjects, 7.7%
were Toxo-positive
Battery of neuropsychological
tests
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
study
Of 4,234 subjects,
20.9% were Toxo-
positive
Battery of neuropsychological
tests
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 didn’t 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
tests’results 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
r´
ıplatov´
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.
CHANGES IN PERSONAL CHARACTERISTICS
AND PHYSICAL APPEARANCE
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 Mount’s (1991) study found that the trait of
conscientiousness—a persistent, planful, responsible,
and hardworking personality—consistently positively
correlates with various indices of a worker’spro-
ductivity (job proficiency, training proficiency, and
personnel data) across different professions. Further-
more, the trait of extroversion—a 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 experience”correlates 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, neuroticism—a personality manifest-
ing emotional instability, anxiety, and lack of psy-
chological adjustment—correlates 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 experiments—which
are clearly unethical—it 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
TABLE 2
Studies on Toxoplasma’s Influence on Human Personality Traits
Study Country Type of study
N(Toxoplasma-
positive/control) Methods Findings
Flegr (2010) Czech
Republic
Convenience
samples
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´
ı
ˇ
cek
(1999)
Czech
Republic
Convenience
sample of women
55/136 Cattell’s 16 Personality Factor
Questionnaire
Infected women had higher intelligence,
lower guilt proneness, and possibly also
higher ergic tension.
Flegr & Hrd´
y
(1994)
Czech
Republic
Convenience
sample
90/248 Cattell’s 16 Personality Factor
Questionnaire
Toxoplasma-positive men had lower
superego strength and protension.
Flegr, Kodym, &
Tolarov´
a
(2000)
Czech
Republic
Convenience
sample of women
230/0; 55/0 Cattell’s 16 Personality Factor
Questionnaire
Affectothymia, surgence, high superego
strength, parmia, and protension were
correlated with the length of the infection.
Flegr, Preiss, &
Klose (2013)
Czech
Republic
Survey of military
personnel
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.
(2003)
Czech
Republic
Survey of military
personnel
229/628 Cloninger’s Temperament and Character
Inventory
Toxoplasma-positive subjects had lower
novelty seeking, impulsiveness,
extravagance, and disorderliness scores.
Infected subjects also had lower IQs.
Flegr, Zitkov´
a,
Kodym, &
Frynta (1996)
Czech
Republic
Convenience
sample
103/291 Cattell’s 16 Personality Factor
Questionnaire
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.
Lindov´
a et al.
(2010)
Czech
Republic
Convenience
sample
56/239 Experimental economic games Infected men were less cooperative and
infected women were more cooperative
compared to their uninfected
counterparts.
Lindov´
a et al.
(2006)
Czech
Republic
Double-blind
testing
(convenience
sample)
49/214 Cattell’s 16 Personality Factor
Questionnaire
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.
Lindov´
a,
Pˇ
r´
ıplatov´
a, &
Flegr (2012)
Czech
Republic
Convenience
sample
47/276 NEO-PI-R Questionnaire Toxoplasma-infected male and female
subjects had higher extroversion and
lower conscientiousness.
Novotn´
a et al.
(2005)
Czech
Republic
Survey of military
personnel
Of 533 subjects, 25.0%
were Toxo-positive
Cloninger’s Temperament and Character
Inventory; Eysenck’s lie scale
Toxoplasma-positive subjects had lower
novelty-seeking scores.
72 FebruaryAcademy of Management Perspectives
TABLE 2
(Continued)
Study Country Type of study
N(Toxoplasma-
positive/control) Methods Findings
Skallov´
a et al.
(2005)
Czech
Republic
Survey of blood
donors
Of 290 subjects, 61.2%
were Toxo-positive
Cloninger’s Temperament and Character
Inventory; Eysenck’s lie scale
Toxoplasma-positive subjects had lower
novelty-seeking scores.
Cook et al.
(2015)
Germany Survey of healthy
controls as a part
of a case-control
study
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.
Khademvatan
et al. (2013)
Iran Convenience
sample
112/125 Cattell’s 16 Personality Factor
Questionnaire
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.
(2016)*
New
Zealand
Population-
representative
birth-cohort
study
236/601 Correlation between various tests and
questionnaires and Toxoplasma
infection
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 didn’t 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,
Lindov´
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,
Kolbekov´
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), it’s
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 teams’and firms’inner 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
infected.
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).
INTERCULTURAL MANAGEMENT
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 “masculine”in 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 organizations’in-
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.
CONCLUSION
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-
dividual’s 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
environment.
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 diem’animal
personality”(Tan et al., 2015, p. 5). As of now there is
only one study that has tested the parasite’s 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 one’s
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
to organizational and management research.
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Petr Houdek (petr.houdek@gmail.com) 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 ´
Ust´
ınad Labem, Czech Republic.
His primary research interests include behavioral econom-
ics, social psychology, and management sciences.
2017 81Houdek
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