Causal inference

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Causal_inference

Causal inference is the process of determining the independent, actual effect of a particular phenomenon that is a component of a larger system. The main difference between causal inference and inference of association is that causal inference analyzes the response of an effect variable when a cause of the effect variable is changed. The science of why things occur is called etiology. Causal inference is said to provide the evidence of causality theorized by causal reasoning.

Causal inference is widely studied across all sciences. Several innovations in the development and implementation of methodology designed to determine causality have proliferated in recent decades. Causal inference remains especially difficult where experimentation is difficult or impossible, which is common throughout most sciences.

The approaches to causal inference are broadly applicable across all types of scientific disciplines, and many methods of causal inference that were designed for certain disciplines have found use in other disciplines. This article outlines the basic process behind causal inference and details some of the more conventional tests used across different disciplines; however, this should not be mistaken as a suggestion that these methods apply only to those disciplines, merely that they are the most commonly used in that discipline.

Causal inference is difficult to perform and there is significant debate amongst scientists about the proper way to determine causality. Despite other innovations, there remain concerns of misattribution by scientists of correlative results as causal, of the usage of incorrect methodologies by scientists, and of deliberate manipulation by scientists of analytical results in order to obtain statistically significant estimates. Particular concern is raised in the use of regression models, especially linear regression models.

Definition

Inferring the cause of something has been described as:

• "...reason[ing] to the conclusion that something is, or is likely to be, the cause of something else".
• "Identification of the cause or causes of a phenomenon, by establishing covariation of cause and effect, a time-order relationship with the cause preceding the effect, and the elimination of plausible alternative causes."

Methodology

General

Further information: Causality and Causal analysis

Causal inference is conducted via the study of systems where the measure of one variable is suspected to affect the measure of another. Causal inference is conducted with regard to the scientific method. The first step of causal inference is to formulate a falsifiable null hypothesis, which is subsequently tested with statistical methods. Frequentist statistical inference is the use of statistical methods to determine the probability that the data occur under the null hypothesis by chance: Bayesian inference is used to determine the effect of an independent variable. Statistical inference in general is used to determine the difference between variations in the original data that are random variation or the effect of a well specified causal mechanism. Notably, correlation does not imply causation, so the study of causality is as concerned with the study of potential causal mechanisms as it is with variation amongst the data. A frequently sought after standard of causal inference is an experiment where treatment is randomly assigned but all other confounding factors are held constant. Most of the efforts in causal inference are in the attempt to replicate experimental conditions.

Epidemiological studies employ different epidemiological methods of collecting and measuring evidence of risk factors and effect and different ways of measuring association between the two. Results of a 2020 review of methods for causal inference found that using existing literature for clinical training programs can be challenging. This is because published articles often assume an advanced technical background, they may be written from multiple statistical, epidemiological, computer science, or philosophical perspectives, methodological approaches continue to expand rapidly, and many aspects of causal inference receive limited coverage.

Common frameworks for causal inference include the causal pie model (component-cause), Pearl's structural causal model (causal diagram + do-calculus), structural equation modeling, and Rubin causal model (potential-outcome), which are often used in areas such as social sciences and epidemiology.

Experimental

Further information: Experiment

Experimental verification of causal mechanisms is possible using experimental methods. The main motivation behind an experiment is to hold other experimental variables constant while purposefully manipulating the variable of interest. If the experiment produces statistically significant effects as a result of only the treatment variable being manipulated, there is grounds to believe that a causal effect can be assigned to the treatment variable, assuming that other standards for experimental design have been met.

Quasi-experimental

Further information: Quasi-experiment

Quasi-experimental verification of causal mechanisms is conducted when traditional experimental methods are unavailable. This may be the result of prohibitive costs of conducting an experiment, or the inherent infeasibility of conducting an experiment, especially experiments that are concerned with large systems such as economies of electoral systems, or for treatments that are considered to present a danger to the well-being of test subjects. Quasi-experiments may also occur where information is withheld for legal reasons.

Approaches in epidemiology

Epidemiology studies patterns of health and disease in defined populations of living beings in order to infer causes and effects. An association between an exposure to a putative risk factor and a disease may be suggestive of, but is not equivalent to causality because correlation does not imply causation. Historically, Koch's postulates have been used since the 19th century to decide if a microorganism was the cause of a disease. In the 20th century the Bradford Hill criteria, described in 1965 have been used to assess causality of variables outside microbiology, although even these criteria are not exclusive ways to determine causality.

In molecular epidemiology the phenomena studied are on a molecular biology level, including genetics, where biomarkers are evidence of cause or effects.

A recent trend is to identify evidence for influence of the exposure on molecular pathology within diseased tissue or cells, in the emerging interdisciplinary field of molecular pathological epidemiology (MPE). Linking the exposure to molecular pathologic signatures of the disease can help to assess causality. Considering the inherent nature of heterogeneity of a given disease, the unique disease principle, disease phenotyping and subtyping are trends in biomedical and public health sciences, exemplified as personalized medicine and precision medicine.

Approaches in computer science

Determination of cause and effect from joint observational data for two time-independent variables, say X and Y, has been tackled using asymmetry between evidence for some model in the directions, X → Y and Y → X. The primary approaches are based on Algorithmic information theory models and noise models.

Noise models

Incorporate an independent noise term in the model to compare the evidences of the two directions.

Here are some of the noise models for the hypothesis Y → X with the noise E:

• Additive noise: ${\displaystyle Y=F(X)+E}$
• Linear noise: ${\displaystyle Y=pX+qE}$
• Post-nonlinear: ${\displaystyle Y=G(F(X)+E)}$
• Heteroskedastic noise: ${\displaystyle Y=F(X)+E.G(X)}$
• Functional noise: ${\displaystyle Y=F(X,E)}$

The common assumption in these models are:

• There are no other causes of Y.
• X and E have no common causes.
• Distribution of cause is independent from causal mechanisms.

On an intuitive level, the idea is that the factorization of the joint distribution P(Cause, Effect) into P(Cause)*P(Effect | Cause) typically yields models of lower total complexity than the factorization into P(Effect)*P(Cause | Effect). Although the notion of "complexity" is intuitively appealing, it is not obvious how it should be precisely defined. A different family of methods attempt to discover causal "footprints" from large amounts of labeled data, and allow the prediction of more flexible causal relations.

Approaches in social sciences

Main article: Causality § Statistics and economics

Social science

The social sciences in general have moved increasingly toward including quantitative frameworks for assessing causality. Much of this has been described as a means of providing greater rigor to social science methodology. Political science was significantly influenced by the publication of Designing Social Inquiry, by Gary King, Robert Keohane, and Sidney Verba, in 1994. King, Keohane, and Verba recommend that researchers apply both quantitative and qualitative methods and adopt the language of statistical inference to be clearer about their subjects of interest and units of analysis. Proponents of quantitative methods have also increasingly adopted the potential outcomes framework, developed by Donald Rubin, as a standard for inferring causality.

While much of the emphasis remains on statistical inference in the potential outcomes framework, social science methodologists have developed new tools to conduct causal inference with both qualitative and quantitative methods, sometimes called a "mixed methods" approach. Advocates of diverse methodological approaches argue that different methodologies are better suited to different subjects of study. Sociologist Herbert Smith and Political Scientists James Mahoney and Gary Goertz have cited the observation of Paul Holland, a statistician and author of the 1986 article "Statistics and Causal Inference", that statistical inference is most appropriate for assessing the "effects of causes" rather than the "causes of effects". Qualitative methodologists have argued that formalized models of causation, including process tracing and fuzzy set theory, provide opportunities to infer causation through the identification of critical factors within case studies or through a process of comparison among several case studies. These methodologies are also valuable for subjects in which a limited number of potential observations or the presence of confounding variables would limit the applicability of statistical inference.

Economics and political science

In the economic sciences and political sciences causal inference is often difficult, owing to the real world complexity of economic and political realities and the inability to recreate many large-scale phenomenona within controlled experiments. Causal inference in the economic and political sciences continues to see improvement in methodology and rigor, due to the increased level of technology available to social scientists, the increase in the number of social scientists and research, and improvements to causal inference methodologies throughout social sciences.

Despite the difficulties inherent in determining causality in economic systems, several widely employed methods exist throughout those fields.

Theoretical methods

Economists and political scientists can use theory (often studied in theory-driven econometrics) to estimate the magnitude of supposedly causal relationships in cases where they believe a causal relationship exists. Theorists can presuppose a mechanism believed to be causal and describe the effects using data analysis to justify their proposed theory. For example, theorists can use logic to construct a model, such as theorizing that rain causes fluctuations in economic productivity but that the converse is not true. However, using purely theoretical claims that do not offer any predictive insights has been called "pre-scientific" because there is no ability to predict the impact of the supposed causal properties. It is worth reiterating that regression analysis in the social science does not inherently imply causality, as many phenomenona may correlate in the short run or in particular datasets but demonstrate no correlation in other time periods or other datasets. Thus, the attribution of causality to correlative properties is premature absent a well defined and reasoned causal mechanism.

Instrumental variables

The instrumental variables (IV) technique is a method of determining causality that involves the elimination of a correlation between one of a model's explanatory variables and the model's error term. The belief here is that, if a model's error term goes hand in hand with the variation of another variable, that the model's error term is probably an effect of variation in that explanatory variable. The elimination of this correlation through the introduction of a new instrumental variable thus reduces the error present in the model as a whole.

Model specification

Model specification is the act of selecting a model to be used in data analysis. Social scientists (and, indeed, all scientists) must determine the correct model to use because different models are good at estimating different relationships.

Model specification can be useful in determining causality that is slow to emerge, where the effects of an action in one period are only felt in a later period. It is worth remembering that correlations only measure whether two variables have similar variance, not whether they affect one another in a particular direction; thus, one cannot determine the direction of a causal relation based on correlations only. Because causal acts are believed to precede causal effects, social scientists can use a model that looks specifically for the effect of one variable on another over a period of time. This leads to using the variables representing phenomena happening earlier as treatment effects, where econometric tests are used to look for later changes in data that are attributed to the effect of such treatment effects, where a meaningful difference in results following a meaningful difference in treatment effects may indicate causality between the treatment effects and the measured effects (e.g., Granger-causality tests). Such studies are examples of time-series analysis.

Sensitivity analysis

Other variables, or regressors in regression analysis, are either included or not included across various implementations of the same model to ensure that different sources of variation can be studied more separately from one another. This is a form of sensitivity analysis: it is the study of how sensitive an implementation of a model is to the addition of one or more new variables.

A chief motivating concern in the use of sensitivity analysis is the pursuit of discovering confounding variables. Confounding variables are variables that have a large impact on the results of a statistical test but are not the variable that causal inference is trying to study. Confounding variables may cause a regressor to appear to be significant in one implementation, but not in another.

Multicollinearity

Another reason for the use of sensitivity analysis is to detect multicollinearity. Multicollinearity is the phenomenon where the correlation between two variables is very high. A high level of correlation between two variables can dramatically affect the outcome of a statistical analysis, where small variations in highly correlated data can flip the effect of a variable from a positive direction to a negative direction, or vice versa. This is an inherent property of variance testing. Determining multicollinearity is useful in sensitivity analysis because the elimination of highly correlated variables in different model implementations can prevent the dramatic changes in results that result from the inclusion of such variables.

However, there are limits to sensitivity analysis' ability to prevent the deleterious effects of multicollinearity, especially in the social sciences, where systems are complex. Because it is theoretically impossible to include or even measure all of the confounding factors in a sufficiently complex system, econometric models are susceptible to the common-cause fallacy, where causal effects are incorrectly attributed to the wrong variable because the correct variable was not captured in the original data. This is an example of the failure to account for a lurking variable.

Design-based econometrics

Recently, improved methodology in design-based econometrics has popularized the use of both natural experiments and quasi-experimental research designs to study the causal mechanisms that such experiments are believed to identify.

Malpractice in causal inference

Despite the advancements in the development of methodologies used to determine causality, significant weaknesses in determining causality remain. These weaknesses can be attributed both to the inherent difficulty of determining causal relations in complex systems but also to cases of scientific malpractice.

Separate from the difficulties of causal inference, the perception that large numbers of scholars in the social sciences engage in non-scientific methodology exists among some large groups of social scientists. Criticism of economists and social scientists as passing off descriptive studies as causal studies are rife within those fields.

Scientific malpractice and flawed methodology

In the sciences, especially in the social sciences, there is concern among scholars that scientific malpractice is widespread. As scientific study is a broad topic, there are theoretically limitless ways to have a causal inference undermined through no fault of a researcher. Nonetheless, there remain concerns among scientists that large numbers of researchers do not perform basic duties or practice sufficiently diverse methods in causal inference.

One prominent example of common non-causal methodology is the erroneous assumption of correlative properties as causal properties. There is no inherent causality in phenomenona that correlate. Regression models are designed to measure variance within data relative to a theoretical model: there is nothing to suggest that data that presents high levels of covariance have any meaningful relationship (absent a proposed causal mechanism with predictive properties or a random assignment of treatment). The use of flawed methodology has been claimed to be widespread, with common examples of such malpractice being the overuse of correlative models, especially the overuse of regression models and particularly linear regression models. The presupposition that two correlated phenomenona are inherently related is a logical fallacy known as spurious correlation. Some social scientists claim that widespread use of methodology that attributes causality to spurious correlations have been detrimental to the integrity of the social sciences, although improvements stemming from better methodologies have been noted.

A potential effect of scientific studies that erroneously conflate correlation with causality is an increase in the number of scientific findings whose results are not reproducible by third parties. Such non-reproducibility is a logical consequence of findings that correlation only temporarily being overgeneralized into mechanisms that have no inherent relationship, where new data does not contain the previous, idiosyncratic correlations of the original data. Debates over the effect of malpractice versus the effect of the inherent difficulties of searching for causality are ongoing. Critics of widely practiced methodologies argue that researchers have engaged statistical manipulation in to publish articles that supposedly demonstrate evidence of causality but are actually examples of spurious correlation being touted as evidence of causality: such endeavors may be referred to as P hacking. To prevent this, some have advocated that researchers preregister their research designs prior to conducting to their studies so that they do not inadvertently overemphasize a nonreproducible finding that was not the initial subject of inquiry but was found to be statistically significant during data analysis.

Slavery in colonial Spanish America

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Slavery_in_colonial_Spanish_America 

Slavery

Contemporary

Historical

Religion

Opposition and resistance

European colonization of the Americas
First wave of European colonization Basque British Curonian Danish Dutch French German Hospitaller Italian Norse Portuguese Russian Scottish Spanish Swedish Colonization of Canada Colonization of the United States Decolonization

Slavery in the Spanish American colonies was an economic and social institution which existed throughout the Spanish Empire including Spain itself. In its American territories, Spain displayed an early abolitionist stance towards indigenous people although Native American slavery continued to be practiced, particularly until the New Laws of 1543. The Spanish empire, however was involved in the enslavement people of African origin. Although the Spanish themselves played a very minor role in the Atlantic slave trade compared to other European empires, in absolute terms, the Spanish Empire was a major recipient of African slaves, with around 22% of the Africans delivered to American shores ending up in the Spanish Empire.

The Spanish restricted and outright forbade the enslavement of Native Americans since the early years of the Spanish Empire with the Laws of Burgos of 1512 and the New Laws of 1542. The latter led to the abolition of the Encomienda, private grants of groups of Native Americans to individual Spaniards as well as to Native American nobility. The implementation of the New Laws and liberation of tens of thousands of Native Americas led to a number of rebellions and conspiracies by "Encomenderos" (Encomienda holders) which had to be put down by the Spanish crown. Asian people (chinos) in colonial Mexico had the same status as Native Americans and thus were forbidden to be enslaved by law.

Spain had a precedent for slavery as an institution since it had existed in Spain itself since the times of the Roman Empire. Slavery also existed among Native Americans of both Meso-America and South America. The Crown attempted to limit the bondage of indigenous people, rejecting forms of slavery based on race. Conquistadors regarded indigenous forced labor and tribute as rewards for participation in the conquest and the Crown gave some conquerors encomiendas. The indigenous people held in encomienda were not slaves, but their under paid labor was mandatory and coerced, while they had rights and could take to trial to their managers, and they were "cared for" by the person in whose charge they were placed (encomendado), this might mean offering them the Christian religion and other perceived (by the Spaniards) benefits of Christian civilization. With the collapse of indigenous populations in the Caribbean, where Spaniards created permanent settlements starting in 1493, Spaniards raided other islands and the mainland for indigenous people to enslave on Hispaniola. With the rise of sugar cultivation as an export product in 1810, Spaniards increasingly utilized enslaved African people for labor on commercial plantations. Although plantation slavery in Spanish America was one aspect of slave labor, urban slavery in households, religious institutions, textile workshops (obrajes), and other venues was also important.

Spanish slavery in the Americas diverged from other European powers in that it took on an early abolitionist stance towards Native American slavery. Although it did not directly partake in the trans-Atlantic slave trade, enslaved Black people were sold throughout the Spanish Empire, particularly in Caribbean territories. During the colonial period, Spanish territories were the most extensive and wealthiest in the Americas. Since Spaniards themselves were barred by the Crown from participating in the Atlantic slave trade, the right to export slaves in these territories, known as the Asiento de Negros was a major foreign policy objective of other European powers, sparking numerous European wars such as the War of Spanish Succession and the War of Jenkin's Ear. In the mid-nineteenth century when most countries in the Americas reformed to disallow chattel slavery, Cuba and Puerto Rico – the last two remaining Spanish American colonies – were among the last, followed only by Brazil.

Enslaved people challenged their captivity in ways that ranged from introducing non-European elements into Christianity (syncretism) to mounting alternative societies outside the plantation (slave labour camp) system (Maroons). The first open Black rebellion occurred in Spanish labour camps (plantations) in 1521. Resistance, particularly to the enslavement of indigenous people, also came from Spanish religious and legal ranks. The first speech in the Americas for the universality of human rights and against the abuses of slavery was also given on Hispaniola, a mere nineteen years after the first contact. Resistance to indigenous captivity in the Spanish colonies produced the first modern debates over the legitimacy of slavery. And uniquely in the Spanish American colonies, laws like the New Laws of 1542, were enacted early in the colonial period to protect natives from bondage. To complicate matters further, Spain's haphazard grip on its extensive American dominions and its erratic economy acted to impede the broad and systematic spread of plantations operated by slave labor. Altogether, the struggle against slavery in the Spanish American colonies left a notable tradition of opposition that set the stage for conversations about human rights.

Iberian precedents to New World slavery

See also: Slavery in Spain § Slavery prior to 1492

 

Alfonso X of Castile and the Siete Partidas

Slavery in Spain can be traced to the times of the Greeks, Phoenicians and Romans. Slavery was cross-cultural and multi-ethnic" and, in addition to that, slavery played an important role in the development of the economy for Spain and other countries.

The Romans extensively utilized slavery for labor and slaves' status was specified in the Code of Justinian. With the rise of Christianity, the status of was altered in that Christians were in theory banned from enslaving fellow Christians, but the practice persisted. With the rise of Islam, and the conquest of most of the Iberian peninsula in the eighth century, slavery declined in remaining Iberian Christian kingdoms. At the time of the formation of Al-Andalus, Muslims were prohibited from enslaving fellow believers, but there was a slave trade of non-Muslims in which Muslims and local Jewish merchants traded in Spanish and Eastern European Christian slaves. Mozarabs and Jews were allowed to remain and retain their slaves if they paid a head tax for themselves and half-value for the slaves. However, non-Muslims were prohibited from holding Muslim slaves, and so if one of their slaves converted to Islam, they were required to sell the slave to a Muslim. Mozarabs were later, by the 9th and 10th centuries, permitted to purchase new non-Muslim slaves via the peninsula's established slave trade.

During the reconquista, Christian Spain sought to retake territory lost to Muslims and this lead to changing norms regarding slavery. Though enslavement of Christians was originally permitted, over the period from the 8th to the 11th centuries the Christian kingdoms gradually ceased this practice, limiting their pool of slaves to Muslims from Al-Andalus. Conquered Muslims were enslaved with the justification conversion and acculturation, but Muslim captives were often offered back to their families and communities for cash payments (rescate). The thirteenth-century code of law, the Siete Partidas of Alfonso "the learned" (1252–1284) specified who could be enslaved: those who were captured in just war; offspring of an enslaved mother; those who voluntarily sold themselves into slavery, and specified slaves' good treatment by their masters. At the time it was generally domestic slavery and was a temporary condition of members of outgroups. As well as the formal parameters for slavery, the Siete Partidas also makes a value judgment, stating that it "was the basest and most wretched condition into which anyone could fall because man, who is the freest noble of all God's creatures, becomes thereby in the power of another, who can do with him what he wishes as with any property, whether living or dead."

Lines dividing the non-Christian world between Castile and Portugal: the 1494 Tordesillas meridian (purple) and the 1529 Zaragoza antimeridian (green)

As the Spanish (Castilians) and Portuguese expanded overseas, they conquered and occupied Atlantic islands off the north coast of Africa, including the Canary Islands as well as São Tomé and Madeira where they introduced plantation sugar cultivation. They considered the indigenous populations there more animal than human, supposedly justifying their enslavement. The Canary Islands came under Castilian control, and by the early sixteenth century the indigenous population had largely been decimated and African slave labor replaced indigenously. Multiple West African states were participants in slave raiding and trading, and the slaves the Castilians purchased were considered legitimate slaves. Slave-trading African states accepted a variety of European goods, including firearms, horses, and other desirable goods in exchange for slaves.

Both the Spanish and the Portuguese colonized the Atlantic islands off the coast of Africa, where they engaged in sugar cane production following the model of Mediterranean production. The sugar complex consisted of slave labor for cultivation and processing, with the sugar mill (ingenio) and equipment established with significant investor capital. When plantation slavery was established in Spanish America and Brazil, they replicated the elements of the complex in the New World on a much larger scale.

The Portuguese exploration of the African coast and the division of overseas territories via the Treaty of Tordesillas meant that the African slave trade was held by the Portuguese. However, demand for African slaves as the Spanish established themselves in the Caribbean meant that became part of the Spanish Empire's social mosaic. Black slaves in Spain were overwhelmingly domestic servants, and increasingly became prestigious property for elite Spanish households though at a much smaller scale than the Portuguese. Artisans acquired black slaves and trained them in their trade, increasing the artisans' output.

Another form of forced labor used in the New World with origins in Spain was the encomienda, on the model of the award of the labor to Christian victors over Muslims during the reconquista. This institution of forced labor was initially employed by the Spaniards in the Canary Islands following their conquest, but the Guanche (Canarian) population precipitously declined. The institution as an institution was much more widespread following the Spanish contact and conquests in Mexico and Peru, but the precedents were set prior to 1492.

Prohibition of forced labor of indigenous peoples

See also: Spanish colonization of the Americas § Spanish Law and indigenous peoples

 

An Aztec slave

 

Viceroy Antonio de Mendoza and Tlaxcalan Indians battle with the Caxcanes in the Mixtón War.

Prior to the Spanish colonization of the Americas, slavery was a common institution among some Pre-Columbian indigenous peoples, particularly the Aztecs. The Spanish conquest and settlement in the New World quickly led to large-scale subjugation of indigenous peoples, mainly of the Native Caribbean people, by Columbus on his four voyages. Initially, forced labor represented a means by which the conquistadores mobilized native labor, with disastrous effects on the population. Unlike the Portuguese Crown's support for the slave trade in Africa, los Reyes Católicos (English: Catholic Monarchs) opposed the enslavement of the native peoples in the newly conquered lands on religious grounds. When Columbus returned with indigenous slaves, they ordered the survivors to be returned to their homelands. In 1512, after pressure from Dominican friars, the Laws of Burgos were introduced to protect the rights of the natives in the New World and secure their freedom. The papal bull Sublimus Dei of 1537, to which Spain was committed, also officially banned enslavement of indigenous peoples, but it was rescinded a year after its promulgation.

The other major form of coerced labor in their colonies, the encomienda system, was also abolished, despite the considerable anger this caused in the conquistador group who had expected to hold their grants in perpetuity. It was replaced by the repartimiento system.

After passage of the 1542 New Laws, also known as the New Laws of the Indies for the Good Treatment and Preservation of the Indians, the Spanish greatly restricted the power of the encomienda system, allowed abuse by holders of the labor grants (encomenderos), and officially abolished the enslavement of the native population. However, indigenous people who rebelled against the Spanish could be enslaved, so that following the Mixtón War (1540-42) in northwest Mexico many indigenous slaves were captured and moved elsewhere in Mexico. The statutes of 1573, within the "Ordinances Concerning Discoveries," forbade unauthorized operations against independent Indian peoples. It required appointment of a "protector de indios", an ecclesiastical representative who acted as the protector of the Indians and represented them in formal litigation. Later in the 16th century, in Peru, thousands of indigenous men were forced to hard work as underground miners in the silver mines of Potosí, by means of the continuation of the pre-Hispanic Inca mita tradition.

Reinstatement of slavery for Mapuche rebels

Main article: Slavery of Mapuches

King Philip III inherited a difficult situation in Chile, where the Arauco War raged and the local Mapuche succeeded in razing seven Spanish cities (1598–1604). An estimate by Alonso González de Nájera put the toll at 3000 Spanish settlers killed and 500 Spanish women taken into captivity by Mapuche. In retaliation the proscription against enslaving Indians captured in war was lifted by Philip in 1608. This decree was abused when Spanish settlers in Chiloé Archipelago used it to launch slave raids against groups such as the Chono of northwestern Patagonia who had never been under Spanish rule and never rebelled. The Real Audiencia of Santiago opined in the 1650s that slavery of Mapuches was one of the reasons for constant state of war between the Spanish and the Mapuche. Slavery for Mapuches "caught in war" was abolished in 1683 after decades of legal attempts by the Spanish Crown to suppress it.

Africans in the early colonial period

Main article: Asiento for the African slave trade to Spanish America

 

Spanish conquistadors in Mexico led by Hernán Cortés. The Spaniards are accompanied by native porters, Malinche, and a black man (holding the horse). Codex Azcatitlan.

When Spain first enslaved Native Americans on Hispaniola, and then replaced them with captive Africans, it established slave labor as the basis for colonial sugar production. It was believed by Europeans that Africans had developed immunities to European diseases, and would not be as susceptible to fall ill as the Native Americans because they had not been exposed to the pathogens yet. In 1501, Spanish colonists began importing enslaved Africans from the Iberian Peninsula to their Santo Domingo colony on the island of Hispaniola. These first Africans, who had been enslaved in Europe before crossing the Atlantic, may have spoken Spanish and perhaps were even Christians. About 17 of them started in the copper mines, and about a hundred were sent to extract gold. As Old World diseases decimated Caribbean indigenous populations in the first decades of the 1500s, enslaved blacks from Africa (bozales) gradually replaced their labor, but they also mingled and joined in flights to freedom, creating mixed-race maroon communities in all the islands where Europeans had established chattel slavery.

Fray Bartolomé de las Casas

Spanish colonist turned Dominican friar Bartolomé de las Casas (1484–1566) observed and recorded the effects of enslavement on the Native populations. Initially he sought to protect the indigenous from enslavement by advocating and participating in the African slavetrade. He later argued that enslavement of both indigenous and Africans was wrong, violating their human rights. Las Casas campaigned for protections of the indigenous, especially crown limits on the exploitation of the encomienda, helping to bring about the 1542 New Laws.

In Spanish Florida and farther north, the first African slaves arrived in 1526 with Lucas Vázquez de Ayllón's establishment of San Miguel de Gualdape on the current Georgia coast. They rebelled and lived with indigenous people, destroying the colony in less than 2 months. More slaves arrived in Florida in 1539 with Hernando de Soto, and in the 1565 founding of St. Augustine, Florida. Native Americans were also enslaved in Florida by the encomienda system. Slaves escaping to Florida from the colony of Georgia were freed by Carlos II's proclamation November 7, 1693 if the slaves were willing to convert to Catholicism, and it became a place of refuge for slaves fleeing the Thirteen Colonies.

In this early period, enslaved African men were often labor bosses, overseeing indigenous labor. Franciscan Toribio de Benavente Motolinia (1482-1568), one of the First Twelve Franciscans to arrive in Mexico in 1524, considered blacks the Fourth Plague on Mexican Indians. He wrote "In the first years these black overseers were so absolute in their maltreatment of the Indians, over-loading them, sending them far from their land and giving them many other tasks that many Indians died because of them and at their hands, which is the worst feature of the situation." In Yucatan, there were regulations attempting to prevent blacks presence in indigenous communities. In Mexico City in 1537, a number of blacks were accused of rebellion. They were executed in the main plaza (zócalo) by hanging, an event recorded in an indigenous pictorial and alphabetic manuscript.

Demand for African slaves was high and the slave trade was controlled by the Portuguese, who set up trading posts on the west coast of Africa. Spanish colonists purchased them directly from Portuguese traders, who in turn purchased them from African traders on the Atlantic coast. With the increased dependency on enslaved Africans and with the Spanish crown opposed to enslavement of indigenous, except in the case of rebellion, slavery became associated with race and racial hierarchy, with Europeans hardening their concepts of racial ideologies. These were buttressed by prior ideologies of differentiation as that of the limpieza de sangre (en: purity of blood), which in Spain referred to individuals without the perceived taint of Jewish or Muslim ancestry. However, in Spanish America, purity of blood came to mean a person free of any African ancestry.

In the vocabulary of the time, each enslaved African who arrived at the Americas was called "Pieza de Indias" (en: a piece of the Indies). The crown issued licenses asientos, to merchants to specifically trade slaves, regulating the trade. During the 16th century, the Spanish colonies were the most important customers of the Atlantic slave trade, claiming several thousands in sales, but other European colonies soon dwarfed these numbers when their demand for enslaved workers began to drive the slave market to unprecedented levels.

Some of the first black people in the Americas were "Atlantic Creoles", as the charter generation is described by the American historian Ira Berlin. Mixed-race men of African and Portuguese/Spanish descent, some slaves and others free, sailed with Iberian ships and worked in the ports of Spain and Portugal; some were born in Europe, others in African ports as sons of Portuguese trade workers and African women. African slaves were also taken to Portugal, where they married local women. The mixed-race men often grew up bilingual, making them useful as interpreters in African and Iberian ports.

Some famous black Spanish soldiers in the first stages of the Spanish conquest of America were Juan Valiente and Juan Beltrán in Chile, Juan Garrido (credited with the first harvesting of wheat planted in New Spain) and Sebastián Toral in Mexico, Juan Bardales in Honduras and Panama, and Juan García [es] in Peru.

The first known and recorded Christian marriage anywhere in the continental United States was an interracial union between a free black Spanish woman from Jerez de la Frontera and a Spanish settler from Segovia who met in Seville and embarked together as a couple to the New World. This marriage took place in 1565 in the Spanish settlement of St. Augustine, Florida.

Estevanico, recorded as a black slave from Morocco, survived the disastrous Narváez expedition from 1527 to 1536 when most of the men died. After the ships, horses, equipment and finally most of the men were lost, with three other survivors, Estevanico spent six years traveling overland from present-day Texas to Sinaloa, and finally reaching the Spanish settlement at Mexico City. He learned several Native American languages in the process. He went on to serve as a well-respected guide. Later, while leading an expedition in what is now New Mexico in search of the Seven Cities of Gold, he was killed in a dispute with the Zuñi local people.

Black slavery in the late colonial period

The population of slaves in Cuba received a large boost when the British captured Havana during the Seven Years' War, and imported 10,000 slaves from their other colonies in the West Indies to work on newly established agricultural plantations. These slaves were left behind when the British returned Havana to the Spanish as part of the 1763 Treaty of Paris, and form a significant part of the Afro-Cuban population today.

While historians have studied the production of sugar on plantations by enslaved workers in nineteenth-century Cuba, they have sometimes overlooked the crucial role of the Spanish state before the 1760s. Cuba ultimately developed two distinct but interrelated sources using enslaved labor, which converged at the end of the eighteenth century. The first of these sectors was urban and was directed in large measure by the needs of the Spanish colonial state, reaching its height in the 1760s. As of 1778, it was reported by Thomas Kitchin that "about 52,000 slaves" were being brought from Africa to the West Indies by Europeans, with approximately 4,000 being brought by the Spanish.

The second sector, which flourished after 1790, was rural and was directed by private slaveholders/planters involved in the production of export agricultural commodities, especially sugar. After 1763, the scale and urgency of defense projects led the state to deploy many of its enslaved workers in ways that were to anticipate the intense work regimes on sugar plantations in the nineteenth century. Another important group of workers enslaved by the Spanish colonial state in the late eighteenth century were the king's laborers, who worked on the city's fortifications.

The Spanish colonies were late to exploit slave labor in the production of sugarcane, particularly on Cuba. The Spanish colonies in the Caribbean were among the last to abolish slavery. While the British abolished slavery by 1833, Spain abolished slavery in Puerto Rico in 1873. On the mainland of colonies, Spain ended African slavery in the eighteenth century. Peru was one of the countries that revived the institution for some decades after declaring independence from Spain in the early 19th century.

Fugitive slaves in Spanish territories

See also: History of slavery in Florida

On May 29, 1680 the Spanish crown decreed that slaves escaping to Spanish territories from Barlovento, Martinique, San Vicente and Granada in the Lesser Antilles would be free if they accepted Catholicism. On September 3, 1680 and June 1, 1685 the crown issued similar decrees for escaping French slaves. On November 7, 1693 King Carlos II issued a decree freeing all slaves escaping from the English colonies who accepted Catholicism. There were similar decrees October 29, 1733, March 11 and November 11, 1740, and September 24, 1850 in the Buen Retiro by Ferdinand VI and the Royal Decree of October 21, 1753.

Since 1687, Spanish Florida attracted numerous African slaves who escaped from slavery in the Thirteen Colonies. Since 1623 the official Spanish policy had been that all slaves who touched Spanish soil and asked for refuge could become free Spanish citizens, and would be assisted in establishing their own workshops if they had a trade or given a grant of land to cultivate if they were farmers. In exchange they would be required to convert to Catholicism and serve for a number of years in the Spanish militia. Most were settled in a community called Gracia Real de Santa Teresa de Mose, the first settlement of free African's in North America. The enslaved African Francisco Menéndez escaped from South Carolina and traveled to St. Augustine, Florida, where he became the leader of the settlers at Mose and commander of the black militia company there from 1726 until sometime after 1742.

The former slaves also found refuge among the Creek and Seminole, Native Americans who had established settlements in Florida at the invitation of the Spanish government. In 1771, Governor of Florida John Moultrie wrote to the Board of Trade, "It has been a practice for a good while past, for negroes to run away from their Masters, and get into the Indian towns, from whence it proved very difficult to get them back." When colonial officials asked the Native Americans to return the fugitive slaves, they replied that they had "merely given hungry people food, and invited the slaveholders to catch the runaways themselves."

After the American Revolutionary War, slaves from the state of Georgia and the Low Country of South Carolina escaped to Florida. The U.S. Army led increasingly frequent incursions into Spanish territory, including the 1817–1818 campaign by Andrew Jackson that became known as the First Seminole War. The United States afterwards effectively controlled East Florida (from the Atlantic to the Appalachicola River). According to Secretary of State John Quincy Adams, the US had to take action there because Florida had become "a derelict open to the occupancy of every enemy, civilized or savage, of the United States, and serving no other earthly purpose than as a post of annoyance to them.". Spain requested British intervention, but London declined to assist Spain in the negotiations. Some of President James Monroe's cabinet demanded Jackson's immediate dismissal, but Adams realized that Jackson's actions had put the U.S. in a favorable diplomatic position. Adams negotiated very favorable terms.

As Florida had become a burden to Spain, which could not afford to send settlers or garrisons, the Crown decided to cede the territory to the United States. It accomplished this through the Adams–Onís Treaty in 1819, effective 1821.

Ending of slavery

Support for abolitionism rose in Great Britain. Slavery in France's Caribbean colonies was abolished by Revolutionary decree in 1794, (slavery in Metropolitan France was abolished in 1315 by Louis X) but was restored under Napoleon I in 1802. Slaves in Saint-Domingue revolted in response and became independent following a brutal conflict. The victorious former slaves founded the republic of Haiti in 1804.

Later slave revolts were arguably part of the upsurge of liberal and democratic values centered on individual rights and liberties which came in the aftermath of the Enlightenment and the French Revolution in Europe. As emancipation became more of a concrete reality, the slaves' concept of freedom changed. No longer did they seek to overthrow the whites and re-establish carbon-copy African societies as they had done during the earlier rebellions; the vast majority of slaves were creole, native born where they lived, and envisaged their freedom within the established framework of the existing society.

On March 22, 1873, Spain abolished slavery in Puerto Rico. The owners were compensated.

The Spanish American wars of independence emancipated most of the overseas territories of Spain; in the Americas, various nations emerged from these wars. The wars were influenced by the ideas of the Age of Enlightenment and economic affairs, which also led to the reduction and ending of feudalism. For example, in Mexico on 6 December 1810, Miguel Hidalgo, leader of the independence movement, issued a decree abolishing slavery, threatening those who did not comply with death. In South America Simon Bolivar abolished slavery in the lands that he conquered. However, it was not a unified process. Some countries, including Peru and Ecuador, reintroduced slavery for some time after achieving independence.

In the treaty of 1814, King Ferdinand of Spain promised to consider means for abolishing the slave trade. In the treaty of September 23, 1817, with Great Britain, the Spanish Crown said that "having never lost sight of a matter so interesting to him and being desirous of hastening the moment of its attainment, he has determined to co-operate with His Britannic Majesty in adopting the cause of humanity." The king bound himself "that the slave trade will be abolished in all the dominions of Spain, May 30, 1820, and that after that date it shall not be lawful for any subject of the crown of Spain to buy slaves or carry on the slave trade upon any part of the coast of Africa." The date of final suppression was October 30. The subjects of the king of Spain were forbidden to carry slaves for any one outside the Spanish dominions, or to use the flag to cover such dealings.

The Assembly of Year XIII (1813) of the United Provinces of the Río de la Plata declared the freedom of wombs. It did not end slavery completely, but emancipated the children of slaves. Many slaves gained emancipation by joining the armies, either against royalists during the War of Independence, or during the later Civil Wars. For example, the Argentine Confederation ended slavery definitely with the sanction of the Argentine Constitution of 1853.

Behavioral contagion

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Behavioral_contagion 

Behavioral contagion is a form of social contagion involving the spread of behavior through a group. It refers to the propensity for a person to copy a certain behavior of others who are either in the vicinity, or whom they have been exposed to. The term was originally used by Gustave Le Bon in his 1895 work The Crowd: A Study of the Popular Mind to explain undesirable aspects of behavior of people in crowds. In the digital age, behavioral contagion is also concerned with the spread of online behavior and information. A variety of behavioral contagion mechanisms were incorporated in models of collective human behavior.

Behavioral contagion has been attributed to a variety of different factors. Often it is distinguished from collective behavior that arises from a direct attempt at social influence. A prominent theory involves the reduction of restraints, put forth by Fritz Redl in 1949 and analyzed in depth by Ladd Wheeler in 1966. Social psychologists acknowledge a number of other factors, which influence the likelihood of behavioral contagion occurring, such as deindividuation (Festinger, Pepitone, & Newcomb, 1952) and the emergence of social norms (Turner, 1964). In 1980, Freedman et al. have focused on the effects of physical factors on contagion, in particular, density and number.

J. O. Ogunlade (1979, p. 205) describes behavioral contagion as a "spontaneous, unsolicited and uncritical imitation of another's behavior" that occurs when certain variables are met: a) the observer and the model share a similar situation or mood (this is one way behavioral contagion can be readily applied to mob psychology); b) the model's behavior encourages the observer to review his condition and to change it; c) the model's behavior would assist the observer to resolve a conflict by reducing restraints, if copied; and d) the model is assumed to be a positive reference individual.

Types of contagion

Social contagion can occur through threshold models that assume that an individual needs to be convinced by a fraction of their social contacts above a given threshold to adopt a novel behaviour. Therefore, the number of exposures will not increase chances of contagion unless the number of source exposures pass a certain threshold. The threshold value can divide contagion processes to two types: 1) Simple contagion and 2) Complex contagion.

Simple contagion

The individual needs only one person displaying the novel behaviour to copy. For instance, cars travel in groups on a two-lane highway since the car in each cluster travels at a slower speed than the car behind it. This relative speed spreads through other cars who slow down to match the speed of the car in front.

Complex contagion

The individual needs to be in contact with two or more sources exhibiting the novel behaviour. This is when copying behaviours needs reinforcement or encouragement from multiple sources. Multiple sources, especially close friends, can make imitation legitimate, credible and worthwhile due to collective effort put in. Examples of complex contagions can be copying risky behaviour or joining social movements and riots.

Factors

Strength of ties

Social contagion in simple contagion models occurs most effectively through 'weak' and 'long' ties between social contacts. A 'weak' tie between two people means they do not interact as frequently and do not influence each other as close friends. However, a relationally 'weak' tie is structurally strong if it is 'long' because it connects socially distant people, showing greater outreach than a relationally 'strong' tie. These 'long' ties allow the flow of new information increasing rate of transmission that relationally strong ties cannot do. Even though close friends can strongly influence each other, they will not help each other learn about new opportunities, ideas or behaviours in socially distant settings if they all know the same things. Few 'weak' and 'long' ties can help spread information quickly between two socially distant strong networks of people. 'Strong' ties within those networks can help spread information amongst the peers.

On the other hand, complex social contagion processes require multiple sources of influence. This is not possible with few 'weak' ties: they need to be long and multiple in number to increase the probability of imitation between socially distant networks.

Structural equivalence

However, social contagion can also occur in the absence of any ties during competition. This happens when two people are structurally equivalent i.e., they occupy the same position in a social network and have the same pattern of relationships with the same people. For instance, two students publishing the same kind of research under the same professor are structurally equivalent. The more similar their relations are with other people i.e. the more substitutable they are with one another, the more they will copy what the other is doing, if it makes them look better, to stay ahead of competition.

Reduction of restraints

Behavioral contagion is a result of the reduction of fear or restraints – aspects of a group or situation which prevent certain behaviors from being performed. Restraints are typically group-derived, meaning that the "observer", the individual wishing to perform a certain behavior, is constrained by the fear of rejection by the group, who would view this behavior as a "lack of impulse control".

An individual (the "observer") wants to perform some behavior, but that behavior would violate the unspoken and accepted rules of the group or situation they are in; these rules are the restraints preventing the observer from performing that action. Once the restraints are broken or reduced the observer is then "free" to perform the behavior; this is achieved by the "intervention" of the model. The model is another individual, in the same group or situation as the observer, who performs the behavior which the observer wished to perform. Stephenson and Fielding (1971) describe this effect as "[Once] one member of a gathering has performed a commonly desired action, the payoffs for similar action or nonaction are materially altered. ... [The] initiator, by his action, establishes an inequitable advantage over the other members of the gathering which they may proceed to nullify by following his example."

Density and number

Density refers to the amount of space available to a person – high density meaning there is less space per person – and number refers to the size of the group. Freedman (1975) put forth the intensification theory, which posits that high density makes the other people in a group more salient features of the environment, this magnifying the individual's reaction to them. Research has shown that high density does in fact increase the likelihood of contagion (Freedman, 1975; Freedman, Birsky, & Cavoukian, 1980). Number also has an effect on contagion, but to a lesser degree than density.

Local trend imitation

However, the probability that an individual will copy a behaviour can also decrease with higher density and number of neighbours. For instance, a person might praise and go to a restaurant with good food based on others’ recommendations but avoid it when it becomes over-crowded. This depicts the local trend imitation phenomenon i.e. the adoption probability first increases with increase in number of adopted neighbours and then decreases.

Identity of the model

Stephenson and Fielding (1971) state that the identity of the model is a factor that influences contagion (p. 81). Depending on the behavior, sex of the model may be a factor in the contagion of that behavior being performed by other individuals – particularly in instances of adult models performing aggressive behavior in the presence of children-observers (Bandura, Ross, & Ross, 1963) {Imitation of film-mediated aggressive models}. In this particular series of experiments – Albert Bandura's Bobo doll experiments from 1961 and 1963 – where the behavior of children was studied after the children watched an adult model punching a bobo doll and the model received a reward, a punishment, or there were no consequences, the analyses revealed that the male model influenced the participants' behavior to a greater extent than did the female model; this was true for both the aggressive and the nonaggressive male models (p. 581).

Dominant leaders

Aggressive behaviour or using coercion, fear or intimidation to imitate a behaviour is known as dominance. People are likely to follow dominant leaders to avoid the cost of punishment. However, such behaviour is more influential amongst children rather than adults: coercive children are thought to be more likeable whereas coercive adults are less likeable and, hence, influential.

Prestigious influencers

While dominant behaviour is displayed in the animal kingdom as well, prestigious behaviour is unique to humans. Unlike animals, we understand the intentions behind someone's actions rather than just being able to copy their movements precisely. This is important since it is easier to learn from the best models rather than learning by ourselves: We might know which behaviour contributes to someone's success at mastering a skill. Hence, we look to see who everyone else is copying i.e. we tend to copy prestigious individuals. Prestigious people enjoy a high degree of influence and respect and are generally the people with the most information.

Ordinary people

A study done on the rate of information transmission via retweets on Twitter found that popular people i.e. people with a large following, are 'inefficient hubs' in spreading concepts. The more followers someone has, the more overloaded they are with information and lower the chances that they will retweet a particular message due to limited attention. Hence, rate of social contagion slows down.

Rather, social contagion can amplify amongst 'ordinary' users with low following if they are closely connected in a peer network. People are more likely to retweet messages by close friends to facilitate social bonding. Peers also have higher similar interests and are more influenced by each other than an 'ordinary' and 'popular' user who do not have mutual ties. Hence, social contagion can occur efficiently amongst tight community structures, in the absence of prestigious and dominant leaders.

Media

Mass media can greatly influence people's opinions and amplify social contagion by reporting stories from socially distant and unconnected networks. They can help to turn minority opinions into the popular opinion, independent of the degree of connectivity between people.

Moreover, Bandura (1977) showed that children can learn and imitate fictitious characters on television.

Personality of the observer

Ogunlade (1979) found that extroverts, who are described as impulsive and sociable individuals, are more likely to be susceptible to contagion than introverted individuals, who are described as reserved and emotionally controlled.

Social norms

Gino, Ayal and Ariely (2009) state that an important factor influencing contagion is the degree to which the observer identifies with the others of the group (p. 394). When identification with the rest of the group is strong, the behaviors of the others will have a larger influence.

However, high homophily or the likelihood of being connected to others with similar interests, can lead to both minority and majority groups overestimating their sizes and vice versa. This can cause people to falsely predict the frequency of their behaviour in the real world since they estimate based on their personal networks. When people overestimate the frequency of a particular behaviour, they may think that they are following social norms and, hence, are less willing to change. Encouraging interactions within heterophilic rather than homophilic social networks can facilitate social contagion more.

Similarities and differences with other types of social influence

Contagion is only one of a myriad of types of social influence.

Conformity / social pressures

Conformity is a type of social influence that is very similar to contagion. It is almost identical to another type of social influence, "pressures toward uniformity" (social pressures) (Festinger, 1954), which differ only in the research techniques they are associated with (Wheeler, 1966, p. 182).

Both conformity and contagion involve some sort of conflict, but differ in the roles other individuals play in that conflict. In conformity, the other individuals of the group try to pressure the observer into performing a behavior; the model then performs some other behavior in the vicinity of the observer. This results in the observer creating restraints against the pressured behavior and a conflict between the pressured behavior and the behavior performed by the model. In the end, the observer either performs the model's behavior his-/herself, rejects the model, or pressures the model to perform the original pressured behavior (Wheeler, Table 1). In contagion, the model's behavior results in the removing of restraints and the resolving of the conflict, while in conformity, the model's behavior results in the creation of restraints and of the conflict.

Social facilitation

See also: Social facilitation in animals

Social facilitation, another type of social influence, is distinguished from contagion, as well as from conformity and social pressures, by the lack of any marked conflict. It is said to occur when the performance of an instinctive pattern of behavior by an individual acts as a releaser for the same behavior in others, and so initiates the same line of action in the whole group (Thorpe, 1956, p. 120). Bandura and Walters (1963, p. 79), give the example of an adult, who has lost the unique aspects of the dialect of the region where they were raised, returns for a visit and "regains" those previously lost patterns of speech. Starch (1911) referred to this phenomenon as an "unintentional or unconscious imitation".

Imitation

Imitation is different from contagion in that it is learned via reward and punishment and is generalized across situations. Imitation can also be a generic term for contagion, conformity, social pressures, and social facilitation.

(Wheeler, 1966, Table 1)	Dynamics of selected influence processes
Stages in influence process	Behavioral contagion	Social pressures and conformity	Social facilitation
Observer's initial conditions	Instigated to BN*. Internal restraints against BN.	Instigated to BP*. No restraints.	No restraints against BN or BP. No instigation to BN or BP.
Model's behavior	Model performs BN.	Model performs BN.	Model performs BN.
Hypothetical processes	Reduction of model's restraints against BN. Fear reduction.	Creation of restraints against BP. Conflict between BN and BP.	Cognitive-behavioral chaining, CS* elicits CR*, inertia overcome.
Observer's behavior	Observer performs BN.	Observer performs BN (or rejects model or induces model to perform BP).	Observer performs BN.

• BN = initial behavior
• BP = pressured behavior
• CS = conditioned stimulus
• CR = conditioned response

Competition contagion on non-competitors

While behavioral contagion is largely about how people might be affected by observations of the expressions or behavior of others, research has also found contagion in the context of a competition where mere awareness of an ongoing competition can have an influence on noncompetitors' task performance, without any information about the actual behavior of the competitors.

Research

Effects of group pressure

Behavioral contagion, largely discussed in the behaviors of crowds, and closely related to emotional contagion, plays a large role in gatherings of two or more people. In the original Milgram experiment on obedience, for example, where participants, who were in a room with only the experimenter, were ordered to administer increasingly more severe electrical shocks as punishment to a person in another room (from here on referred to as the "victim"), the conflict or social restraint experienced by the participants was the obligation to not disobey the experimenter – even when shocking the victim to the highest shock level given, a behavior which the participants saw as opposing their personal and social ideals (Milgram, 1965, p. 129).

Milgram also conducted two other experiments, replications of his original obedience experiment, with the intent being to analyze the effect of group behavior on participants: instead of the subject being alone with the experimenter, two confederates were utilized. In the first of the two experiments, "Groups for Disobedience", the confederates defied the experimenter and refused to punish the victim (p. 130). This produced a significant effect on the obedience of the participants: in the original experiment, 26 of the 40 participants administered the maximum shock; in the disobedient groups experiment, only 4 of 40 participants administered the highest level of voltage (Table 1). Despite this high correlation between shock level administered and the obedience of the group in the disobedient groups experiment, there was no significant correlation for the second of the replicated experiments: "Obedient Groups", where the confederates did not disobey the experimenter and, when the participant voiced angst regarding the experiment and wished to stop administering volts to the victim, the confederates voiced their disapproval (p. 133). Milgram concludes the study by remarking that "the insertion of group pressure in a direction opposite that of the experimenter's commands produces a powerful shift toward the group. Changing the group movement does not yield a comparable shift in the [participant's] performance. The group success in one case and failure in another can be traced directly to the configuration of motive and social forces operative in the starting situation." That is, if the group's attitudes are similar to or compatible with the participant's/observer's, there is a greater likelihood that the participant/observer will join with the group (p. 134).

Overweight and obesity

Network phenomena are relevant to obesity, which appears to spread through social ties. Teenagers of US Army families assigned to counties with higher obesity rates were more likely to become overweight or obese in a 2018 study. This effect could not be explained by self-selection (homophily) or shared built environments and is attributed to social contagion.