This investigation sheds light on the social history of pathogenic dirt and its significance for shaping medical practices during the nineteenth century. It consists of an analysis focusing on Swedish medicine, using 8800 yearly reports written 1820–1900 by Swedish provincial doctors for the National Board of Health in Stockholm. The main argument is that the provincial doctors’ perceptions of the relationship between dirt and health during this century can be better understood by focusing on similarities in the handling of different kinds of pathological dirt over the course of many decades, rather than seeing interest in cleanliness as something mostly unprecedented. A novel cleanliness regime became dominant during the latter third of the century, meant to counter a new hybrid between everyday dirt – bodily emanations from healthy bodies – and matter believed to have caused miasmatic and contagionistic disease. New ideas about filth and its impact on health played a crucial role in the development of public health and sanitation movements, and were a precondition for everyday dirt becoming a central medical problem around the turn of the twentieth century, but as is shown, they built on old precedents. Thus, the miasmatic and contagionistic approach to disease shaped conceptions of hygiene and cleanliness.

This article explores the sudden spate of stories concerning the so-called “blue gum negro” (the Blue Gum) that circulated in the national press from the late 1880s to the late 1890s. These reports concerned purportedly blue-gummed, Black assailants, whose bite was alleged to be poisonous, and of whom African Americans were supposedly terrified. This article argues that, although these narratives reinforced white notions of Black criminality and credulity, they marked a particular moment of racialization, in which fears of bodily contagion, generated by the recent revolution in germ theory, were harnessed to notions of embodied racial difference, to express and galvanize white anxieties about racial impurity. Because Blue Gums embodied dysgenic menace, white journalists and writers were often reluctant to disavow their existence, instead capitalizing on the slippage between figurative and literal language that characterized discourse on race. However, in appropriating Black culture and presenting a figure from folklore as a racial type, white writers betrayed not only the essentially superstitious character of racial thought but also the interwoven nature of dominant and subjugated cultures in the United States.

The coronavirus pandemic has created a new awareness of epidemics, and insurance companies have been reminded to consider the risk related to infectious diseases. This paper extends the traditional multi-state models to include epidemic effects. The main idea is to specify the transition intensities in a Markov model such that the impact of contagion is explicitly present in the same way as in epidemiological models. Since we can study the Markov model with contagious effects at an individual level, we consider individual risk and reserves relating to insurance products, conforming with the standard multi-state approach in life insurance mathematics. We compare our notions with other but related notions in the literature and perform numerical illustrations.

We assessed the reaction of American adults to scenarios involving explicit types of exposure to live COVID viruses in June 2020, in the first months of the COVID pandemic. Four features of magical contagion are physical contact focus, insensitivity to elapsed time (‘permanence’), insensitivity to sterilization (‘spiritual essence’), and insensitivity to dose. We demonstrated the operation of all four features in a majority of participants. We also report another dramatic demonstration of the principle of dose insensitivity. When asked for the minimal number of COVID viruses that would have to enter their lung to give them a 50% chance of contracting COVID, more than half of subjects responded with ‘one’. Magical contagion should generally function to increase fear and perceived risk of COVID.

Contagion across various types of connections is a central process in the study of many political phenomena (e.g., democratization, civil conflict, and voter turnout). Over the last decade, the methodological literature addressing the challenges in causally identifying contagion in networks has exploded. In one of the foundational works in this literature, Shalizi and Thomas (2011, Sociological Methods and Research 40, 211–239.) propose a permutation test for contagion in longitudinal network data that is not confounded by selection (e.g., homophily). We illustrate the properties of this test via simulation. We assess its statistical power under various conditions of the data, including the nature of the contagion, the structure of the network through which contagion occurs, and the number of time periods included in the data. We then apply this test to an example domain that is commonly considered in the context of observational research on contagion—the international spread of democracy. We find evidence of international contagion of democracy. We conclude with a discussion of the practical applicability of the Shalizi and Thomas test to the study of contagion in political networks.

Backward magical contagion describes instances in which individuals (sources) express discomfort or pleasure when something connected to them (medium; e.g., hair, a diary) falls into the possession of a negatively- or positively-perceived individual (recipient). The reaction seems illogical, since it is made clear that the source will never experience the object again, and the psychological effect appears to reverse the standard forward model of causality. Backward magical contagion was originally believed to be a belief held only within traditional cultures. Two studies examined negative backward contagion in adult Americans in online surveys. Study 1 indicated that backward contagion effects occur commonly, particularly when a recipient knows of the medium’s source. Study 2 showed that backward contagion effects tend to be neutralized when the recipient burns the object, as opposed to just possessing it or discarding it. Ironically, in traditional cultures, burning is a particularly potent cause of backward contagion.

Individuals avoid objects that have been in physical contact with morally offensive or disgusting entities. This has been called negative magical contagion, an implicit belief in the transmission of essence by physical contact. Alternatively, individuals may avoid a negatively contaminated object because: 1) the object is a strong reminder of the original contagion source (association account); or 2) the act of interacting with the object signals specific information about the self (social communication account). We report that: 1) people often prefer to interact with an entity that they believe is more associated with a negative source rather than an entity that is less associated but has made physical contact with the same negative source; 2) while an associative account requires that contact enhances association, a study of memory for visual pairings of objects indicates that when objects are touching, their associative link (recall) is no greater than when they are in proximity; and 3) subjects continue to show aversion to (prefer to wear gloves to handle) an object that contacted a negative entity even if they are handling the object in order to physically destroy it, hence strongly signaling their rejection of that object. Association and social communication are at best partial accounts for contagion effects.

This is a first study on attachment to national and sacred land and land as a protected value. A measure of attachment to the land of Israel is developed and administered to two groups, Jewish college students in Israel and the United States. Levels of land attachment are high and not significantly different in the two groups, with a great deal of variation. Land may become more important through being inhabited by a group over centuries. This is a positive contagion effect, and is opposed in some cases by negative contagion produced when the “enemies” live on the land for some period of time. We demonstrate a significant correlation of positive contagion sensitivity with attachment to the land of Israel. Unlike many other cases of the interaction of positive and negative contagion, negative contagion does not overwhelm positive contagion in the domain of land attachment. We also present evidence for linkages between political positions, religiosity, importance of Israel, Arab aversion, and vulnerability of Israel with attachment to land, but these do not fully account for the contagion effects. A number of significant differences between Israelis and Americans are described.

We propose the concept of ‘scientific contagion’ — a mental heuristic through which any form of scientific treatment transfers some essence of ‘science’ to the processed substance, thereby affecting its nature and social acceptability. This was tested regarding the potential treatment of water from natural sources before it is used for religious purposes, as many such sources have dangerous pollutants. For an ancient natural well having a religious narrative, most participants judged that the acceptability of water would be reduced for religious purposes but not for drinking if local officials scientifically treat the water. That is not the case if religious rituals are conducted on the water instead (Study 1). If water from a “holy river” is processed scientifically, most participants predicted that it would reduce acceptability for religious use while increasing acceptability for drinking (Study 2). Potential scientific treatment without altering the composition of water from a natural spring also decreased acceptability for religious use but there was no effect on acceptability for drinking or on willingness to pay money for the water (Study 3). A follow-up study comparing acceptability for different kinds of water sources — from a holy well, natural spring, and household tap water sourced from either underground wells or rivers found lower acceptability for religious usage compared to drinking after potential scientific treatment for all these waters, but more so for holy and natural waters (Study 4). These studies establish the phenomena of scientific contagion that could have significant social implications and open future directions.

Contagion refers to the belief that individuals or objects can acquire the essence of a particular source, such as a disgusting product or an immoral person, through physical contact. This paper documents beliefs in a "contact-free" form of contagion whereby an object is thought to inherit the essence of a person when it was designed, but never actually physically touched, by the individual. We refer to this phenomenon as contagion through creative intent or “intention-based contagion” and distinguish it from more traditional forms of contact-based contagion (Studies 1 and 2), as well as alternative mechanisms such as mere association (Studies 2 and 3a). We demonstrate that, like contact-based contagion, intention-based contagion results from beliefs in transferred essence (Study 1) and involves beliefs in transfer of actual properties (Study 4). However, unlike contact-based contagion, intention-based contagion does not appear to be as strongly related to the emotion of disgust (Study 1) and can influence evaluations in auditory as well as visual modalities (Studies 3a–3c).

Naturalness is important and valued by most lay Western individuals. Yet, little is known about the lay meaning of “natural”. We examine the phenomenon of additivity dominance: adding something to a natural product (additive) reduces naturalness more than removing an equivalent entity (“subtractive”). We demonstrate additivity dominance for the first time using equivalent adding and subtracting procedures. We find that adding something reduces naturalness more than removing the same thing (e.g., adding pulp to orange juice reduces naturalness more than removing pulp from orange juice; Study 1); an organism with a gene added is less natural than one with a gene removed (Study 2); and framing a product as an additive (versus as a subtractive) reduces naturalness (Study 3). We begin to examine accounts of additivity dominance. We find that it is not due to the connotations of the word “additive” (Study 4). However, data are consistent with an extra processing account — where additives involve more processing (extracting and adding) than subtractives (only removing) — and with a contagion account — where adding is more contaminating than removing (Study 5).

En este artículo se analizan las circunstancias históricas en las cuales cambiaron, tanto el discurso médico como la atención que se daba a las personas con lepra en Puerto Rico. Se toma como punto de partida la invasión estadounidense de 1898 y su proyecto de transformación de la salud pública de la isla. Como parte de estos cambios se identifica un nuevo modelo de atención para los contagiados, basado en la idea del aislamiento. De esta manera, las autoridades sanitarias se distanciaban de la teoría de la herencia, la que se había manejado con anterioridad a esa fecha. Se argumenta que ese aislamiento fue expresión de la política colonialista del momento. Se quiere mostrar que la rigurosidad del nuevo modelo de atención transformó la vida de aquellos enfermos, los cuales pasaron de convivir con sus familias, a recluirse en un islote. Este proceso de transformación fue iniciado particularmente por los médicos del Marine Hospital Service.

Across a wide variety of applications, the self-exciting Hawkes process has been used to model phenomena in which the history of events influences future occurrences. However, there may be many situations in which the past events only influence the future as long as they remain active. For example, a person spreads a contagious disease only as long as they are contagious. In this paper, we define a novel generalization of the Hawkes process that we call the ephemerally self-exciting process. In this new stochastic process, the excitement from one arrival lasts for a randomly drawn activity duration, hence the ephemerality. Our study includes exploration of the process itself as well as connections to well-known stochastic models such as branching processes, random walks, epidemics, preferential attachment, and Bayesian mixture models. Furthermore, we prove a batch scaling construction of general, marked Hawkes processes from a general ephemerally self-exciting model, and this novel limit theorem both provides insight into the Hawkes process and motivates the model contained herein as an attractive self-exciting process in its own right.