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Nothing Ventured, Nothing Gained: Parasite Infection is Associated with Entrepreneurial Initiation, Engagement and Performance
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Abstract
There is growing evidence that human biology and behavior is influenced by infectious microorganisms. One such microorganism is the protozoan Toxoplasma gondii (TG). Using longitudinal data covering the female population of Denmark, we extend research on the relationship between TG infection and entrepreneurial activity and outcomes. Results indicate that TG infection is associated with a subsequent increase in the probability of becoming an entrepreneur, and is linked to other outcomes including venture performance. With parasite behavioral manipulation antithetical to rational judgement, we join a growing conversation on biology and alternative drivers of business venturing.
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https://www.researchgate.net/publication/338857788_Nothing_Ventured_Nothing_Gained_Parasite_Infection_is_Associated_with_Entrepreneurial_Initiation_Engagement_and_Performance ]
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This article elaborates on a lively and rapidly evolving conversation central to entrepreneurship: the underpinnings of entrepreneurial action. In particular, we respond to a critique published in this journal by Brown, Packard, and Bylund (BPB), in which they argue that all EA is based on intendedly-rational judgment. The empirical reality of rational, deliberative intentionality in entrepreneurship is beyond dispute and we have argued that behavioral logics do not simply supplant intendedly-rational ones. However, mounting evidence suggests that the wide-spectrum framework developed by Lerner, Hunt and Dimov – ranging from impulse-driven, a-rational action to deeply deliberative, rational action – offers a more veridical and useful perspective. Although BPB's critique succeeds in underscoring the exciting challenges facing entrepreneurship scholars; in our view, the critique largely relies on philosophical argumentation and definitional boundary-setting that are inconsistent with decades of scientific advancement in the psychological sciences. Given this, and recent empirical evidence from entrepreneurship scholars, we think it would be counter-productive to consider entrepreneurship as the sole domain of human activity completely circumscribed by rational judgment.
Entrepreneurship is multifaceted. The purpose of this review is to acknowledge and critically assess the many and varied dependent variables (DVs) of entrepreneurship over the last 17 years. By focusing exclusively on systematically reviewing entrepreneurship’s DVs, this paper maps out, classifies, and provides order to the phenomena that scholars consider part of this self-defined field of research. Using a systematic selection process and an inductive approach to categorization, we offer a meta-framework for organizing entrepreneurship’s DVs. Based on this meta-framework, entrepreneurship involves the (a) initiation, (b) engagement, and (c) performance of entrepreneurial endeavors embedded in (d) environmental conditions, in which an entrepreneurial endeavor is the investment of resources into the pursuit of a potential opportunity. For each category, we offer both a review of the different DVs and opportunities for future research.
Disciplines such as business and economics often rely on the assumption of rationality when explaining complex human behaviours. However, growing evidence suggests that behaviour may concurrently be influenced by infectious microorganisms. The protozoan Toxoplasma gondii infects an estimated 2 billion people worldwide and has been linked to behavioural alterations in humans and other vertebrates. Here we integrate primary data from college students and business professionals with national-level information on cultural attitudes towards business to test the hypothesis that T. gondii infection influences individual- as well as societal-scale entrepreneurship activities. Using a saliva-based assay, we found that students (n = 1495) who tested IgG positive for T. gondii exposure were 1.4× more likely to major in business and 1.7× more likely to have an emphasis in 'management and entrepreneurship' over other business-related emphases. Among professionals attending entrepreneurship events, T. gondii-positive individuals were 1.8× more likely to have started their own business compared with other attendees (n = 197). Finally, after synthesizing and combining country-level databases on T. gondii infection from the past 25 years with the Global Entrepreneurship Monitor of entrepreneurial activity, we found that infection prevalence was a consistent, positive predictor of entrepreneurial activity and intentions at the national scale, regardless of whether previously identified economic covariates were included. Nations with higher infection also had a lower fraction of respondents citing 'fear of failure' in inhibiting new business ventures. While correlational, these results highlight the linkage between parasitic infection and complex human behaviours, including those relevant to business, entrepreneurship and economic productivity.
Objectives:
Latent toxoplasmosis modifies various hormones and behaviors in infected hosts and possibly involves in etiology of different neurologic and psychiatric disorders. The aim of the current study was to assess possible associations between latent toxoplasmosis and testosterone concentration in Toxoplasma infected and free subjects. Briefly, 18-49 year-old participated in the study. After collected blood samples, sera were analyzed for the detection of anti-Toxoplasma IgG antibody. Totally, 76 positive sera were selected as study group (38 from men and 38 from women) and a same number of negative sera as control group.
Results:
Comparison of testosterone concentrations and control groups showed that testosterone concentration in study group was higher than that in control group with statistically significant difference (P = 0.024 and P = 0.043 for men and women, respectively). Significant differences were found in testosterone concentrations and anti-Toxoplasma IgG antibody levels in study and control groups (P < 0.05). Toxoplasmosis can affect the mean concentration of serum testosterone in human. Alteration of testosterone during latent toxoplasmosis can result in alterations in behavioral, physiologic and immunological parameters in long time.
The article is a perspective on utilization of microorganisms and chemosignals in studying human economic behavior. Research in biological roots of economic development has already confirmed that parasitic pressure influenced the creation and development of cultural norms and institutions. However, other effects of microorganisms on human groups and individual decision-making and behavior are heavily understudied. The perspective discusses how parasitic infections, sexually transmitted organisms and microbiota (i.e., "human holobiont") could causally influence risk-seeking behavior, impulsivity, social dominance, empathy, political views and gender differences. As a case study, the parasite Toxoplasma gondii and its influence on economic preferences, personal characteristics and human appearance are examined. I also briefly review how chemosignals influence decision-making, particularly in the social preferences domain. I mention some predictions that arise from the paradigm of economic holobiont for the economic science. The conclusion summarizes limitations of the discussed findings and the stated speculations.
Mental disorders are prevalent, place considerable burden on the economy and lead to suffering for those with the disorders and their loved ones. However, there is a flipside. Evidence suggests that people with mental disorders can flourish and productively contribute to society through entrepreneurship. This paper explores the relationship between mental disorders and entrepreneurship. It builds a research agenda to propose that researchers explore the role of mental disorders in the entrepreneurial context. We show how such research will advance this new field of research, but also how it can develop novel insights and theories in entrepreneurship and contribute to theories on the psychology of work, career choice, and clinical psychology.
Whether business venturing emerges in the context of nascent-stage start-ups or corporate giants, one of the enduring and fundamental assumptions underlying theories of entrepreneurial action is that entrepreneurs operate in uncertain environments. And yet, nearly a century since the unveiling of Knightian uncertainty as a precursor to profit-making, the identification, description and operationalization of uncertainty as a construct continues to exhibit conflicting definitions, tautological measures, and unwitting conflation with more apt, more precise constructs in entrepreneurship and organization theory. The purpose of this study is to review the multiple research streams that together constitute the literature on knowledge problems to identify critical boundary conditions of uncertainty as an analytical construct. Based on this review, we then set forth a multi-level research agenda for exploring entrepreneurial action under conditions of ambiguity, complexity, equivocality, and uncertainty.
Prior studies find sizable gaps between entrepreneurial intentions and subsequent actions. We extend models of entrepreneurial intentions by drawing on action phase theory to better understand how entrepreneurial intentions translate into actions. Our study focuses on the effects of implementation intentions on taking entrepreneurial action. The analysis uses two waves of survey data on 422 individuals, from the Swedish general population, who had an explicit interest in starting a business and who reported on their actions 6 months later. We test and find support for a moderated mediation model in which implementation intentions mediate the effects of goal intentions on taking entrepreneurial action. We further find the mediated effect to be even stronger for those confirming a strong intention to start a new business. We provide an in-depth discussion of the concept of implementation intention and an extensive research agenda.
Dazed and confused by the wild hype surrounding gazelles and unicorns, entrepreneurship researchers have focused on the black swans of the entrepreneurial world, even though IPOs and venture capital financing of firms are extremely rare events. Despite their rarity, entrepreneurship conferences and journals have been filled with papers on various aspects of the process of “going public” and “VC networks.” Fortunately, in the middle of the Silicon Valley mania, other scholars have been paying attention to the mundane aspects of business startups – – the ordinary business starts, numbering in the hundreds of thousands each year in the United States for businesses with employees. We point out what we believe to be scholars’ misplaced attention to the extreme and their corresponding neglect of the mundane. Correcting the misperception that has been introduced into the literature by selection biases favoring growing and profitable firms will give scholars and policymakers a more accurate and policy-relevant picture of entrepreneurship in the 21st century.
In this article, we conduct a systematic review of the emerging literature on the biological perspective in management and investigate research spanning the areas of genetics, physiology, and neuroscience. We examine 291 papers published in 133 journals over an 85-year period as well as 10 conference/working papers and six books. On the basis of this analysis, we present an organizing framework of the area, explain the mechanisms through which biological factors relate to management, and discuss the implications of the biological perspective for the theory and the practice of management. Finally, we present an agenda highlighting avenues for future research in this field.
Impulsive individuals are attracted to uncertain contexts, such as entrepreneurship, and are more likely to act despite this uncertainty. Thus, impulsivity may represent an asset in entrepreneurship. This paper outlines a conceptual framework and develops detailed propositions for the multifaceted influence of impulsivity on entrepreneurial action. It moves beyond entrepreneurship as a deliberate cognitive process to sufficiently account for how uncertainty influences action. In so doing, this paper constitutes a counterweight to the extensive examinations of positive personal attributes in entrepreneurship research. It also suggests a context in which a common trait with strong negative connotations may be advantageous.
Keywords:
Impulsivity; entrepreneurship; uncertainty
Understanding the psychological nature and development of the individual entrepreneur is at the core of contemporary entrepreneurship research. Since the individual functions as a totality of his or her single characteristics (involving the interplay of biological, psychosocial, and context-related levels), a person-oriented approach focusing on intraindividual dynamics seems to be particularly fruitful to infer realistic implications for practice such as entrepreneurship education and promotion. Applying a person-oriented perspective, this paper integrates existing psychological approaches to entrepreneurship and presents a new, person-oriented model of entrepreneurship, the Entrepreneurial Personality System (EPS). In the empirical part, this model guided us to bridge two separate research streams dealing with entrepreneurial personality: research on broad traits like the Big Five and research on specific traits like risk-taking, self-efficacy, and internal locus of control. We examine a gravity effect of broad traits, as assumed in the EPS framework, by analyzing large personality data sets from three countries. The results reveal a consistent gravity effect of an intraindividual entrepreneurial Big Five profile on the more malleable psychological factors. Implications for entrepreneurship research and practice are discussed.
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.
Attention-deficit/hyperactivity (ADHD) symptoms have been associated with the decision to become self-employed. Although these symptoms are generally regarded as disadvantageous, there may also be a bright side. To our knowledge, however, there has been no systematic, epidemiological evidence to support this claim. This paper examines the association between ADHD symptoms and self-employment in a population-based sample from the STAGE cohort of the Swedish Twin Registry (N = 7208). For replication, we used a sample of Dutch students who participated in the Global University Entrepreneurial Spirit Students' Survey (N = 13,112). In the Swedish sample, we found a positive association with self-employment for both general ADHD symptoms [odds ratio (OR) 1.13; 95 % confidence intervals (CI) 1.04-1.23] and hyperactivity symptoms [OR 1.19; 95 % CI 1.08-1.32], whereas no association was found for attention-deficit symptoms [OR 0.99; 95 % CI 0.89-1.10]. The positive association between hyperactivity and self-employment was replicated in the Dutch student sample [OR 1.09; 95 % CI 1.03-1.15]. Our results show that certain aspects of ADHD, in particular hyperactivity, can have a bright side, as they are positively associated with self-employment.
Toxoplasma gondii (T. gondii), a protozoan parasite that persists in host tissues, including brain, has been associated with several psychiatric disorders and with suicidal behavior. We sought to test the hypothesis that latent T. gondii infection, as manifest by circulating immunoglobulin G (IgG) antibodies to T. gondii, is associated with both categorical and dimensional measures of aggression.IgG antibodies to T. gondii were collected between 1991 and 2008 from 358 adult subjects with DSM-5 intermittent explosive disorder (IED), non-IED psychiatric disorders (psychiatric controls), or no evidence of any psychiatric diagnosis (healthy controls). Assessments of aggression, anger, and impulsivity, as well as state/trait anger, depression, and anxiety were completed. T. gondii seropositive status (IgG > 12 IU) was the primary outcome measure for this study.T. gondii seropositive status (IgG > 12 IU) was associated with higher aggression (P = .022) and impulsivity (P = .05) scores. When both aggression and impulsivity scores were controlled for, however, only aggression scores were higher in seropositive subjects (P = .011). In addition, T. gondii seropositive status and marginal mean ± SE aggression scores increased from healthy controls (9.1% and -0.66 ± 0.05) to psychiatric controls (16.7% and -0.27 ± 0.05) to subjects with IED (21.8% and 1.15 ± 0.06; P ≤ .05). These findings were not accounted for by the presence of other syndromal/personality disorders or by states or traits related to depressed or anxious moods.These data are consistent with previous studies suggesting a relationship between T. gondii and self-directed aggression (ie, suicidal behavior) and further add to the biological complexity of impulsive aggression both from a categorical and a dimensional perspective.
Background:
Past research linked Toxoplasma gondii (TG) infection in humans with neurological and mental disorders (e.g., schizophrenia, Alzheimer's disease and attention disorders), irregularities of the dopaminergic and testosterone system, and increased likelihood of being involved in traffic accidents.
Methodology/principal findings:
We test for an association between TG infection and financial decision-making (DM) using a case-control design in a sample of female Czech students (n = 79). We estimate each subject's risk attitude and loss aversion using an experimental economic task involving real monetary incentives. We find no significant evidence that either measure of decision-making is associated with TG infection.
Conclusion:
We were unable to find evidence of an association between TG infection and financial decision-making in females.
This paper develops and tests a model of an individual's intention to reenter entrepreneur-ship following business exit. Two long-standing theories, prospect theory and self-efficacy, seem to develop opposite predictions in this context. To reconcile these conflicting predictions , we theorize a moderating model and test the boundary conditions of both theories. Relying on two experimental studies, we find that prospect theory explains reentry intentions of entrepreneurs who have lost money when their self-efficacy is moderate or low. Thereby, we provide an explanation for the puzzling empirical finding that so many failed entrepreneurs reenter entrepreneurship even if failure has undermined their self-efficacy.
This study examines the relationship between prenatal testosterone exposure (PTE) and selection into entrepreneurship. We argue that the relationship between PTE and entrepreneurial intent is positive and mediated by general and domain-specific risk-taking related to financial investment and professional career. Using the second-to-fourth digit ratio (2D:4D) as noninvasive retrospective marker for PTE, we identify two-step mediation effects of PTE on entrepreneurial intent through both general and domain-specific risk-taking. To account for possible socialization-based effects, we control for gender and parental self-employment. Applying ordinary least square regression analyses and structural equation models, we provide empirical evidence for a biological association between 2D:4D and entrepreneurial intent.
Human personality traits which can be reliably measured by any of a number of rating scales, show a considerable heritable component. The tridimensional personality questionnaire (TPQ) is one such instrument and was designed by Cloninger to measure four distinct domains of temperament - Novelty Seeking, Harm Avoidance, Reward Dependence and Persistence-that are hypothesized to be based on distinct neurochemical and genetic substrates. Cloninger proposed that individual variations in the Novelty Seeking trait are mediated by genetic variability in dopamine transmission. Individuals who score higher than average on the TPQ Novelty Seeking scale are characterized as impulsive, exploratory, fickle, excitable, quick-tempered and extravagant, whereas those who score lower than average tend to be reflective, rigid, loyal, stoic, slow-tempered and frugal. We now show that higher than average Novelty Seeking test scores in a group of 124 unrelated Israeli subjects are significantly associated with a particular exonic polymorphism, the 7 repeat allele in the locus for the D4 dopamine receptor gene (D4DR). The association of high Novelty Seeking and the 7-repeat allele was independent of ethnicity, sex or age of the subjects. This work, together with the accompanying confirmations in this issue, provides the first replicated association between a specific genetic locus involved in neurotransmission and a normal personality trait.
Psychologists and psychiatrists tend to be little aware that (a) microbes in our brains and guts are capable of altering our behavior; (b) viral DNA that was incorporated into our DNA millions of years ago is implicated in mental disorders; (c) many of us carry the cells of another human in our brains; and (d) under the regulation of viruslike elements, the paternally inherited and maternally inherited copies of some genes compete for domination in the offspring, on whom they have opposite physical and behavioral effects. This article provides a broad overview, aimed at a wide readership, of the consequences of our coexistence with these selfish entities. The overarching message is that we are not unitary individuals but superorganisms, built out of both human and nonhuman elements; it is their interaction that determines who we are.
© The Author(s) 2015.
To what extent does formal schooling, one of the most prominent manifestations of human capital, affect entrepreneurship perform-ance? And, how large are these returns to education for entrepreneurs relative to employees? These are the questions we address and answer in this paper. Based on a meta-analysis of studies analyzing the rela-tionship between schooling and entrepreneurship, we demonstrate that the effect of formal schooling on entrepreneur performance has not yet been consistently measured, due to shortcomings in the em-pirical strategies applied so far. We discuss these shortcomings as well as some potential solutions. Then, we will discuss two recent applica-tions of such more advanced empirical strategies. The first of these studies shows that in the US, the returns to education are much higher for entrepreneurs than for employees (14 and 10 percent, re-spectively). This difference in estimated returns has been insignificant when using OLS. The second study pertains to Europe, i.e. it deals with the Netherlands. It shows again that OLS-estimates of the re-turns to education are biased downwards. Moreover, the distinct and direct effect of human capital is usually obscured by its indirect effect through the extent of capital constraints. The total effect of approxi-mately 14 percent is shown to consist of a direct effect of 12.7 per-cent and an indirect effect, through the extent of capital constraints, of approximately 1.3 percent. We conclude with several policy impli-cations that are based on the novel finding that the returns to educa-tion are higher for entrepreneurs than for employees. * Justin van der Sluis is a Ph.D. student at the University of Amsterdam and af-filiated with the Tinbergen Institute. Mirjam van Praag is an Associate Professor at the University of Amsterdam and affiliated with the Tinbergen Institute.
Background
Toxoplasmosis is becoming a global health hazard as it infects 30-50% of the world human population. Clinically, the life-long presence of the parasite in tissues of a majority of infected individuals is usually considered asymptomatic. However, a number of studies show that this 'asymptomatic infection' may also lead to development of other human pathologies.Aims of the studyThe purpose of the study was to collect available geoepidemiological data on seroprevalence of toxoplasmosis and search for its relationship with mortality and disability rates in different countries.Methods and findingsPrevalence data published between 1995-2008 for women in child-bearing age were collected for 88 countries (29 European). The association between prevalence of toxoplasmosis and specific disease burden estimated with age-standardized Disability Adjusted Life Year (DALY) or with mortality, was calculated using General Linear Method with Gross Domestic Product per capita (GDP), geolatitude and humidity as covariates, and also using nonparametric partial Kendall correlation test with GDP as a covariate. The prevalence of toxoplasmosis correlated with specific disease burden in particular countries explaining 23% of variability in disease burden in Europe. The analyses revealed that for example, DALY of 23 of 128 analyzed diseases and disease categories on the WHO list showed correlations (18 positive, 5 negative) with prevalence of toxoplasmosis and another 12 diseases showed positive trends (p
Scholars use the theoretical lens of bias to research various behavioral phenomena in entrepreneurship. We assess this body of research, focusing on definitional issues and relationships. Furthermore, we discuss how the study of bias in entrepreneurship can be advanced, given the new development in related fields such as cognitive sciences. The assessments and discussions help reveal as well as address tensions in the literature, identify numerous research opportunities that may not be obvious by looking at previous work individually, and contribute to how the theory of bias can further help to understand entrepreneurship.
The role of personality traits in the decision to start a business and to maintain it successfully is discussed controversially in entrepreneurship research. Our meta-analysis builds upon and extends earlier meta-analyses by doing a full analysis of personality traits that includes a comparison of different traits from a theoretical perspective and by analysing a full set of personality predictors for both start-up activities as well as success. Theoretically, our article adds to the literature by matching traits to the tasks of entrepreneurs. The results indicate that traits matched to the task of running a business produced higher effect sizes with business creation than traits that were not matched to the task of running an enterprise, corrected r = .247, K = 47, N = 13,280, and corrected r = .124, K = 20, N = 3975, respectively. Moreover, traits matched to the task produced higher correlations with success, corrected r = .250, K = 42, N = 5607, than traits not matched to the task of running a business, corrected r = .028, K = 13, N = 2777. The traits matched to entrepreneurship significantly correlated with entrepreneurial behaviour (business creation, business success) were need for achievement, generalized self-efficacy, innovativeness, stress tolerance, need for autonomy, and proactive personality. These relationships were of moderate size in general and, moreover, heterogeneity suggested that future research should analyse moderator variables.
The parasite Toxoplasma gondii influences the behaviour of infected animals and probably also personality of infected humans. Subjects with a Rhesus-positive blood group are protected against certain behavioural effects associated with Toxoplasma infection, including the deterioration of reaction times and personality factor shift.
Here, we searched for differences in the toxoplasmosis-associated effects between RhD-positive and RhD-negative subjects by testing 502 soldiers with two personality tests and two intelligence tests. The infected subjects expressed lower levels of all potentially pathognomic factors measured with the N-70 questionnaire and in neurasthenia measured with NEO-PI-R. The RhD-positive, Toxoplasma-infected subjects expressed lower while RhD-negative, Toxoplasma-infected subjects expressed higher intelligence than their Toxoplasma-free peers. The observed Toxoplasma-associated differences were always larger in RhD-negative than in RhD-positive subjects.
RhD phenotype plays an important role in the strength and direction of association between latent toxoplasmosis and not only psychomotor performance, but also personality and intelligence.
The parasitic protozoan Toxoplasma gondii infects about one-third of the population of developed countries. The life-long presence of dormant stages of this parasite in the brain and muscular tissues of infected humans is usually considered asymptomatic from the clinical point of view. In the past 20 years, research performed mostly on military personnel, university students, pregnant women and blood donors has shown that this 'asymptomatic' disease has a large influence on various aspects of human life. Toxoplasma-infected subjects differ from uninfected controls in the personality profile estimated with two versions of Cattell's 16PF, Cloninger's TCI and Big Five questionnaires. Most of these differences increase with the length of time since the onset of infection, suggesting that Toxoplasma influences human personality rather than human personality influencing the probability of infection. Toxoplasmosis increases the reaction time of infected subjects, which can explain the increased probability of traffic accidents in infected subjects reported in three retrospective and one very large prospective case-control study. Latent toxoplasmosis is associated with immunosuppression, which might explain the increased probability of giving birth to a boy in Toxoplasma-infected women and also the extremely high prevalence of toxoplasmosis in mothers of children with Down syndrome. Toxoplasma-infected male students are about 3 cm taller than Toxoplasma-free subjects and their faces are rated by women as more masculine and dominant. These differences may be caused by an increased concentration of testosterone. Toxoplasma also appears to be involved in the initiation of more severe forms of schizophrenia. At least 40 studies confirmed an increased prevalence of toxoplasmosis among schizophrenic patients. Toxoplasma-infected schizophrenic patients differ from Toxoplasma-free schizophrenic patients by brain anatomy and by a higher intensity of the positive symptoms of the disease. Finally, five independent studies performed in blood donors, pregnant women and military personnel showed that RhD blood group positivity, especially in RhD heterozygotes, protects infected subjects against various effects of latent toxoplasmosis, such as the prolongation of reaction times, an increased risk of traffic accidents and excessive pregnancy weight gain. The modern human is not a natural host of Toxoplasma. Therefore, it can only be speculated which of the observed effects of latent toxoplasmosis are the result of the manipulation activity of the Toxoplasma aimed to increase the probability of its transmission from a natural intermediate to the definitive host by predation, and which are just side effects of chronic infection.
Found worldwide from Alaska to Australasia, Toxoplasma gondii knows no geographic boundaries. The protozoan is the source of one of the most common parasitic infections in humans, livestock, companion animals, and wildlife, and has gained notoriety with its inclusion on the list of potential bioterrorism microbes. In the two decades since the publication of the first edition of Toxoplasmosis of Animals and Humans there has been an explosion of knowledge concerning T. gondii and toxoplasmosis. Still used extensively as a cell model, its genome has recently been published making it a subject of even greater scientific interest. Keeping the organizational style that made the previous edition so popular and usable, this second edition has been completely revised and updated. New in the Second Edition: Expanded information on the cultivation, maintenance, and preservation of T. gondii Expanded information on the cell biology and molecular biology of the parasite Reviews all literature from the past 20 years for each domestic animal Summarizes information on the worldwide prevalence of toxoplasmosis in pregnant women and the devastating disease it can cause in newborn Written by one of the pioneers of the field, the book provides unique information on all known host types for this parasite. It distills the voluminous and potentially confusing scientific literature that has grown geometrically in the 20 years since the publication of the first edition into a comprehensive resource. The single author approach ensures a strong foundation in the biology and a seamless integration of topics. The new edition of this groundbreaking work is the only volume to cover toxoplasmosis of animals and humans thoroughly in one source. It supplies an entry point to further research by cutting through the morass of literature to identify the most relevant references.
Previously, we reported that Toxoplasma gondii (T. gondii)-seropositivity is associated with higher impulsive sensation seeking in younger men. As dopaminergic and serotonergic signaling regulate impulsivity, and as T. gondii directly and indirectly affects dopaminergic signaling and induces activation of the kynurenine pathway leading to the diversion of tryptophan from serotonin production, we investigated if dopamine and serotonin precursors or the tryptophan metabolite kynurenine interact with the T. gondii–impulsivity association. In 950 psychiatrically healthy participants, trait impulsivity scores were related to T. gondii IgG seropositivity. Interactions were also identified between categorized levels of phenylalanine (Phe), tyrosine (Tyr), Phe:Tyr ratio, kynurenine (Kyn), tryptophan (Trp) and Kyn:Trp ratio, and age and gender. Only younger T. gondii-positive men with a high Phe:Tyr ratio, were found to have significantly higher impulsivity scores. There were no significant associations in other demographic groups, including women and older men. No significant effects or interactions were identified for Phe, Tyr, Kyn, Trp, or Kyn:Trp ratio. Phe:Tyr ratio, therefore, may play a moderating role in the association between T. gondii seropositivity and impulsivity in younger men. These results could potentially lead to individualized approaches to reduce impulsivity, based on combined demographic, biochemical and serological factors.
A number of world literature reports indicate that a latent Toxoplasma gondii infection leads to development of central nervous system disorders, which in turn may lead to altered behavior in the affected individuals. T. gondii infection has been observed to play the greatest role in drivers, suicides, and psychiatric patients. Studies conducted for this manuscript involve a different, never before really reported correlation between latent T. gondii infection and ethanol abuse. A total of 538 decedents with a known cause of death were included in the study. These individuals were divided into three groups: the risky behavior group, inconclusively risky behavior group, and control group. The criterion for this division was the likely effect of the individual's behavior on the mechanism and cause of his/her death. The material used for analyses were blood samples collected during routine medico-legal examinations in these cases. The blood samples were used to measure anti-T. gondii IgG antibodies with an enzyme-linked immunosorbent assay (ELISA). Moreover, the following data were recorded for each decedent: sex, age, circumstances of death, cause of death, time from death to autopsy, and (if provided) substance abuse status (alcohol, illicit drugs). In those cases where blood alcohol level or toxicology tests were requested by the Prosecutor's Office, their results were also included in our analysis. Test results demonstrated a strong correlation between latent T. gondii infection and engaging in risky behaviors leading to death. Moreover, analyses demonstrated a positive correlation between the presence of anti-T. gondii IgG antibodies and psychoactive substance (especially ethanol) abuse, however, the causal relationship remains unclear. Due to the fact that alcohol abuse constitutes a significant social problem, searching for eliminable risk factors for addiction is extremely important. Our analyses provided new important information on the possible effects of latent T. gondii infection in humans.
Recently, entrepreneurship scholars have started to show interest in how " negative " traits associated with mental disorders such as ADHD may have positive implications in entrepreneur-ship. While this research has the potential of producing important and counter-intuitive results, it is still in its infancy and the causal mechanisms that drive those individuals to be attracted to entrepreneurship have received limited attention. Consequently, we draw on the person-environment fit literature and propose that individuals are attracted to, and engage in, entrepreneurship because the task environment of entrepreneurship which favors speed of action is aligned with the traits of those individuals. We develop and test a model which suggests that ADHD influences entrepreneurship through the multifaceted trait of impulsivity. We find that inattention is negatively but hyperactivity is positively associated with entrepre-neurship. We also find that sensation seeking and lack of premeditation generally positively influences entrepreneurship, whereas urgency has the opposite influence. Taken together, this suggests complex, multifaceted implications of ADHD and impulsivity in entrepreneurship. Theoretical implications of these findings are discussed. Research on entrepreneur personality has been mostly associated with positive traits, such as self-efficacy and achievement motivation. However, most traits are not universally positive or negative and what is functional or dysfunctional depends on context (Judge et al., 2009). Entre-preneurship is characterized by uncertainty, which indices anxiety, worry, procrastination and inaction among most people (McMullen and Shepherd, 2006; Paulus, 2007). However, it is also a vocation that grants more autonomy in terms of job design and task allocation, which may be attractive to individuals who need more leeway in designing their own tasks. Acknowledging the high uncertainty and autonomy in entrepreneurship, we argue that ADHD symptoms, which are associated with negative consequences in many areas of life, may have positive implications in the context of entrepreneurship because ADHD is characterized by traits such as sensation seeking, a focus on action with little premeditation, and a desire for autonomy. We employ person-environment fit theory (e.g., Holland, 1997) to argue that ADHD symptoms influence entrepreneurial preferences and behavior through the multi-dimensional traits of im-pulsivity. Specifically, ADHD symptoms are related to higher levels of sensation seeking, lack of premeditation, lack of perseverance and urgency. These traits in turn influence the perceived attractiveness of entrepreneurship and the probability of starting a business. We conducted surveys on a sample of MBA alumni from a school that is consistently ranked as one of the top fifty public MBA programs, who by virtue of their degree tend to have viable job opportunities and were thus less likely to be pushed into entrepreneurship. We find that ADHD symptoms have a complicated relationship with entrepreneurial preferences and action, with the pathway through sensation seeking and lack of premeditation being mostly positive while the pathway through urgency being negative. Further, hyperactive symptoms seem to mainly result in positive outcomes while inattention symptoms lead to negative ones. Our findings demonstrate that entrepreneurship is indeed a unique area where negative traits, such as ADHD, may represent valuable assets. Previous research has mostly associated ADHD with negative job-related outcomes (Barkley et al., 2006). Our research indicates that certain aspects of ADHD symptoms, such as sensation seeking and lack of premeditation, could lead individuals to be attracted to entrepreneurship and to start their own businesses. This suggests a contextualized view of personality traits, as well as boundary conditions to existing theories. Second, we develop and empirically test a model that links ADHD symptoms to entrepreneur-ship through the multi-dimensional traits of impulsivity, which provides a more nuanced and theoretically interesting understanding of the ADHD—entrepreneurship relationship. The same can be said about our findings of the differential influences of inattention and hyperactivity symptoms. Thus, this paper contributes to previous research on ADHD and entrepreneurship that has mostly examined the bivariate relationship between the two (e.g., Veryheul et al., 2015; Thurik et al., 2016). Finally, our post-hoc analyses showed that the effects of ADHD symptoms on entrepreneurship are more pronounced under highly uncertain environments. This is consistent with our theorizing, suggesting that individuals with ADHD symptoms are more likely to harness advantages associated with ADHD rather than suffer from associated disadvantages in highly uncertain and dynamic environments such as entrepreneurship. There are at least two important practice implications of our results. First, our results imply that individuals with ADHD symptoms may be empowered to craft their own jobs to fit their special needs. Second, our findings suggest that people with ADHD symptoms and impul-sivity will tend to prefer action speed over action accuracy and that this may be functional in the context of entrepreneurship.
Does testosterone increase the tendency to engage in self-employment? The results presented to date have been mixed. Using three different studies, we provide additional evidence on the relationship between testosterone and self-employment. Drawing on a cross section of 2,146 individuals (1,178 males and 968 females) from the National Health and Nutrition Examination Surveys’ 2011–2012 sample, and controlling for endogeneity (with red blood cell count, percentage hematocrit, and zinc supplement intake in the past 30 days as instruments), we find that serum testosterone levels are positively associated with self-employment for males (marginally significant, two-tailed test). As testosterone levels could be affected by social, economic, and biological factors during one’s life course, we draw more robust inferences by assessing whether the 2D:4D digit ratio, a marker of prenatal testosterone exposure, influences the likelihood of self-employment. From Understanding Society’s Innovation Panel Wave 6, we tested separate models for 449 males and 525 females, and our results indicate that males (respectively, females) with a lower 2D:4D ratio in their left hand, or higher prenatal testosterone exposure, have a significantly greater (respectively, marginally significant) likelihood of self-employment (two-tailed test). Finally, we examine the twin testosterone transfer effect in a sample of opposite-sex and same-sex twins from the National Survey of Midlife Development in the United States and provide additional support for the marginally significant (two-tailed test) positive association between testosterone and self-employment.
Data are available at https://doi.org/10.1287/mnsc.2016.2664 .
This paper was accepted by Toby Stuart, entrepreneurship and innovation.
Although there has been abundant research on the positive personality and environmental qualities that stimulate entrepreneurship, we argue that negative personal circumstances of an economic, sociocultural, cognitive, and physical/ emotional nature may have an equally powerful role to play in getting people to become effective entrepreneurs. These challenges create conditions and experiences that motivate particular adaptive requirements which in turn foster outcomes such as work discipline, risk tolerance, social and network skills, and creativity.
Decision making under risk involves balancing the potential of gaining rewards with the possibility of loss and/or punishment. Tolerance to risk varies between individuals. Understanding the biological basis of risk tolerance is pertinent because excessive tolerance contributes to adverse health and safety outcomes. Yet, not much is known about biological factors mediating inter-individual variability in this regard. We investigate if latent Toxoplasma gondii infection can cause risk tolerance. Using a rodent model of the balloon analogous risk task, we show that latent T. gondii infection leads to a greater tolerance of reward forfeiture. Furthermore, effects of the infection on risk can be recapitulated with testosterone supplementation alone, demonstrating that greater testosterone synthesis by the host post-infection is sufficient to change risk tolerance. T. gondii is a frequent parasite of humans and animals. Thus, the infection status can potentially explain some of the inter-individual variability in the risky decision making.
Toxoplasma gondii infection has previously been described to cause infected mice to lose their fear of cat urine. This behavioral manipulation has been proposed to involve alterations of host dopamine pathways due to parasite-encoded aromatic amino acid hydroxylases. Here, we report successful knockout and complementation of the aromatic amino acid hydroxylase AAH2 gene, with no observable phenotype in parasite growth or differentiation in vitro and in vivo. Additionally, expression levels of the two aromatic amino acid hydroxylases were negligible both in tachyzoites and in bradyzoites. Finally, we were unable to confirm previously described effects of parasite infection on host dopamine either in vitro or in vivo, even when AAH2 was over-expressed using the BAG1 promoter. Together, these data indicate that AAH enzymes in the parasite do not cause global or regional alterations of dopamine in the host brain, although they may locally affect this pathway. Additionally, our findings suggest alternative roles for the AHH enzymes in T. gondii since AAH1 is essential for growth in non-dopaminergic cells.
Copyright © 2014, American Society for Microbiology. All Rights Reserved.
This paper offers an analytical structure to pinpoint the behavioral roots of superior performance, where "behavioral" denotes "being about mental processes." Such roots are identified in behavioral deviations from market efficiency. The causes of these deviations are behavioral factors that bound firms' ability to pursue and compete for superior opportunities.Because these bounds are systematic and diffused among firms, they ensure that latent opportunities are noLcompeted away.In this setting, the behavioral bases of superior performance stem from a superior ability to overcome focal behavioral bounds. This analytical structure is used to identify the mental processes especially important to firm performance that strategic leaders can reliably manage. Its key insight is that superior opportunities are cognitively distant. They rarely correspond to common ways of thinking. The reason for this is that it is necessary to overcome strong behavioral bounds to pursue these opportunities. This insight contrasts with mainstream behavioral approaches to strategy, which focus on the virtues of local action, and it has two implications: the behavioral essence of superior performance corresponds to strategic leaders' superior ability to manage the mental processes necessary to pursue cognitively distant opportunities; and pursuing the cognitively distant implies a more expansive conception of strategic agency (e.g., the role of strategic leaders) than is acknowledged by mainstream behavioral approaches to strategy. The challenges posed by this conception require a model of human cognition that goes beyond the understanding of bounded rationality that is diffused in current behavioral strategy research. The second part of the paper assesses the traits of a model of human mind that can support the behavioral conception of strategic agency advocated and proposes a unified model of the human mind that centers on associative processes.
Do cultural attitudes affect institutions and economic performance? This paper suggests they do. To measure the impact of cultural attitudes we use prevalence rates of the common parasite Toxoplasma gondii which is known to affect individual attitudes and societal values in predictable ways. By using prevalence rates of Toxoplasma as instrument for cultural variation, we are able to isolate the effects of cultural attitudes on institutions, distinguishing them from effects of institutions and economic outcomes on culture. We find that our indicators of cultural attitudes are significant determinants of institutional quality, and strong predictors of long-run economic performance.
The analysis of the decision to enter into self-employment is a hot topic in economic literature. Among the elements that most directly influence this decision, individual factors are central. This study produces a comprehensive survey of the impact of these factors, covering both the theoretical arguments and the main conclusions emerging from the empirical studies. We analyze twelve critical determinant factors of the entry into self-employment grouped into seven categories: (i) basic individual characteristics (gender, age, and marital status and children); (ii) family background (parents and spouse); (iii) personality characteristics (risk attitude and other psychological traits); (iv) human capital (education and experience); (v) health condition; (vi) nationality and ethnicity; and (vii) access to financial resources.
While for some of the factors solid conclusions can be found, for others additional research is still needed in order to shed further light on their influence.
abstract The emergent literature on dynamic capabilities and their role in value creation is riddled with inconsistencies, overlapping definitions, and outright contradictions. Yet, the theoretical and practical importance of developing and applying dynamic capabilities to sustain a firm's competitive advantage in complex and volatile external environments has catapulted this issue to the forefront of the research agendas of many scholars. In this paper, we offer a definition of dynamic capabilities, separating them from substantive capabilities as well as from their antecedents and consequences. We also present a set of propositions that outline (1) how substantive capabilities and dynamic capabilities are related to one another, (2) how this relationship is moderated by organizational knowledge and skills, (3) how organizational age affects the speed of utilization of dynamic capabilities and the learning mode used in organizational change, and (4) how organizational knowledge and market dynamism affect the likely value of dynamic capabilities. Our discussion and model help to delineate key differences in the dynamic capabilities that new ventures and established companies have, revealing a key source of strategic heterogeneity between these firms.
The protozoan parasite Toxoplasma gondii enhances the sexual attractiveness of infected male rats and attenuates the innate fear of cat odour in infected individuals. These behavioural changes plausibly lead to greater transmission of parasites through sexual and trophic routes, respectively. Testosterone, a testicular steroid, is known to reduce fear and enhance sexual attractiveness in males. Here, we show that Toxoplasma gondii infection enhances expression of genes involved in facilitating synthesis of testosterone, resulting in greater testicular testosterone production in male rats. In several species, testosterone mediates trade-offs between sexually selected traits and life history decisions. Augmentation of testosterone synthesis by Toxoplasma gondii suggests that parasites may manipulate these trade-offs in rats.