Monday, February 3, 2020

Echo Chambers Exist! (But They're Full of Opposing Views)

Echo Chambers Exist! (But They're Full of Opposing Views). Jonathan Bright, Nahema Marchal, Bharath Ganesh, Stevan Rudinac. arXiv Jan 30 2020. arXiv:2001.11461

Abstract: The theory of echo chambers, which suggests that online political discussions take place in conditions of ideological homogeneity, has recently gained popularity as an explanation for patterns of political polarization and radicalization observed in many democratic countries. However, while micro-level experimental work has shown evidence that individuals may gravitate towards information that supports their beliefs, recent macro-level studies have cast doubt on whether this tendency generates echo chambers in practice, instead suggesting that cross-cutting exposures are a common feature of digital life. In this article, we offer an explanation for these diverging results. Building on cognitive dissonance theory, and making use of observational trace data taken from an online white nationalist website, we explore how individuals in an ideological 'echo chamber' engage with opposing viewpoints. We show that this type of exposure, far from being detrimental to radical online discussions, is actually a core feature of such spaces that encourages people to stay engaged. The most common 'echoes' in this echo chamber are in fact the sound of opposing viewpoints being undermined and marginalized. Hence echo chambers exist not only in spite of but thanks to the unifying presence of oppositional viewpoints. We conclude with reflections on policy implications of our study for those seeking to promote a more moderate political internet.

Check also The rise in the political polarization in recent decades is not accounted for by the dramatic rise in internet use; claims that partisans inhabit wildly segregated echo chambers/filter bubbles are largely overstated:
Deri, Sebastian. 2019. “Internet Use and Political Polarization: A Review.” PsyArXiv. November 6.

And Testing popular news discourse on the “echo chamber” effect: Does political polarisation occur among those relying on social media as their primary politics news source? Nguyen, A. and Vu, H.T. First Monday, 24 (5), 6. Jun 4 2019.

Mating with immature females is an alternative tactic for brown widow males, since adult females cannibalize mating males & immature females do not; but males approached and preferred to mate with adult females

Alternative mating tactics in a cannibalistic widow spider: do males prefer the safer option? Lenka Sentensk√°, Gabriele Uhl, Yael Lubin. Animal Behaviour, Volume 160, February 2020, Pages 53-59.

•    Mating with immature females is an alternative tactic for brown widow males.
•    Adult females cannibalize mating males, but immature females do not.
•    Males approached and preferred to mate with adult females over receptive immatures.
•    Males did not show a preference for unreceptive versus late-stage receptive immatures.
•    Close-range cues in webs of immatures may indicate receptivity.

Abstract: Mating generally occurs with adult females, which undergo a suite of changes in morphology, physiology and behaviour during maturation. In the brown widow spider, Latrodectus geometricus, however, males can mate with immature females during a short period before they moult to the adult stage. Mating with immature females seems beneficial for males, because they are not at risk of being cannibalized, whereas cannibalism inevitably occurs in matings with adult females. We conducted choice experiments to elucidate male preference, courtship and mating behaviour with immature and adult females of different ages. We controlled for age of the females’ webs to provide males with potential web-borne attractants of similar age. We tested whether males distinguish immature females that are ready to mate (late subadult stage) from adult females and from immature females that do not mate (early subadults), and we examined male response to young versus old adult females. Males approached and mated with adult females more frequently than late subadult females, but there were no differences in the frequencies of approach to early and late subadults or to adult females of different ages. Once on the web, however, males attempted to mate with the late subadults. We suggest that web-borne volatile cues, typical of adult females, may be reduced or lacking in late subadult females, yet less volatile cues may indicate receptivity.


Male L. geometricus mated with late subadult females, which would seem to be highly advantageous for the male due to the reduced courtship combined with consistently successful copulation with both palps and lack of sexual cannibalism (Biaggio et al., 2016, Waner et al., 2018; this study). However, when we presented males with late subadult and adult females simultaneously, they typically chose adult, cannibalistic females over the noncannibalistic subadult females. Males showed this preference even when we controlled for web age, a confounding factor that might have affected their choice for adult females observed in a previous study (Waner et al., 2018).

Sexual Attractants

Male L. geometricus might not recognize subadult females as potential mates due to a lack of sex pheromone (Waner et al., 2018). For example, Fisher et al. (2018) suggested that subadult females of the false black widow spider, Steatoda grossa, do not produce a sexual-attractant pheromone. However, male widow spiders are often found on webs of subadult females in nature (Y. Lubin, personal observation). Furthermore, males readily approached the subadult females in their webs, when we exposed the males to late subadult females against an empty control and they did so as rapidly as when they approached adult females. These observations suggest that even before the final moult females produce cues that act as sexual attractants by which males recognize subadult females as potential mates.
In our experiments, we found no evidence that the age of adult females influenced the male's response in choice tests, contrary to previous findings (Waner et al., 2018) where males preferred older adult females to young adults and late stage subadults. The result of Waner et al. (2018) was probably due to the presence of a stronger pheromone cue that had accumulated in the older web. We also observed no difference in the male's approach towards late subadult females, which are ready to mate, and early subadult females, which are not. This suggests that males cannot identify from a distance whether the subadult females are ready to mate. However, after contacting their webs, males courted the early subadult females only very briefly and then remained in their webs without any further courting, but males immediately courted and then mated with late subadult females. Thus, our observations agree with other studies on spider chemical communication, which suggest that airborne chemicals provide less specific information than chemicals detected by contact with the web (reviewed in Gaskett, 2007, Uhl, 2013). Similarly, when presented with adult and late subadult females, males seemed to recognize the female stage only upon contacting the web because only then did they begin to add silk when with an adult female or vibrate when with a late subadult female.
The observed preference of males for adult rather than subadult females could be due to quantitative differences in male-attracting signals or to different cues emitted by subadult and adult females. Virgin adult females of many spider species attract males by producing pheromones that signal readiness to mate (Gaskett, 2007, Kasumovic and Andrade, 2004, Riechert and Singer, 1995, Roberts and Uetz, 2005, Stoltz et al., 2007, Uhl, 2013). Subadult mating in L. geometricus occurs during a 4-day period before the final moult (late subadult stage). In general, adults seem to produce more pheromone and thus provide a stronger signal than immature females and often only adults produce pheromones (Gaskett, 2007, Uhl and Elias, 2011, Uhl, 2013, Fischer et al., 2018). Then, the observed preference for adult females represents rather an attraction to a stronger signal than a preference for a certain stage per se. A few pheromones have been chemically characterized for virgin adult females (e.g. in the genus Latrodectus; Jerhot, Stoltz, Andrade, & Schulz, 2010) but none for subadults. Although males often cohabit with subadult females (Jackson, 1986), these females might not produce sex pheromones, and males may identify them by unintentionally produced chemical cues (Fischer, 2019). Therefore, olfactory cues produced by subadult females may be qualitatively different from pheromones of adult females, potentially allowing males to differentiate between the two stages. If these chemicals are distinguishable by males, the choice of adult females over late subadults might indicate that the former are perceived as higher-quality mates, even though mating with them limits males to a single copulation and sometimes even to a single insertion (Segoli, Arieli, et al., 2008).

Costs to Males of Mating with Subadult Females

There may be fitness costs to males adopting the subadult mating tactic. After mating, subadult-mated females still have to undergo a final moult to adulthood and may have a lower probability of surviving to oviposition than adult-mated females. The moulting process itself is a sensitive period due to the risk of predation on moulting or freshly moulted spiders, the risk of desiccation or an inability to release the old cuticle (e.g. Horner and Starks, 1972, Jones, 1941, Tanaka, 1984). Thus, males may prefer to mate with adult females due to the overall greater probability of successful reproduction.
Costs of mating with late subadult females could also arise from the specific mating behaviour and the mechanisms of copulation, sperm transfer and sperm storage. When mating with subadult females, L. geometricus males do not somersault and are not cannibalized. In the congener L. hasselti, cannibalism reduces the likelihood of a female remating (Andrade, 1996). Thus, the lack of cannibalism might lead to a greater probability of remating in subadult-mated females and consequently to paternity loss for the first male. Furthermore, during courtship with adult females, the male removes a large part of the female's web and adds his own silk. Webs of adult female L. hasselti that were thus altered by males attracted fewer suitors (Scott, Kirk, McCann, & Gries, 2015), a phenomenon observed also in other web-building species (reviewed in Scott, Anderson, & Andrade, 2018). By contrast, we showed here that webs of subadult-mated females were not altered by the male; male courtship was brief, the web remained intact and the male added little silk. A subsequent male might thus have no indication of a previous visitor. It is unclear whether subadult-mated females remain attractive to males and whether these females will remate after maturing to adults (Biaggio et al., 2016, Waner et al., 2019). Finally, although mating with a subadult female enables the male to seek an additional female, high mortality during mate search (more than 80% of L. hasselti males die without finding a mate; Andrade, 2003) may reduce the benefit of such matings.
A male mating with subadult females may have lower paternity than expected for the first male in adult matings due to unfavourable sperm storage conditions or incorrect placement of sperm in the subadult female spermathecae, or to lower competitive ability of his sperm against a second male's sperm. If the internal genitalia of late subadult females are not fully developed, sperm storage conditions may differ from those in adult females and might result in a lower paternity share for a male's sperm when competing with ejaculates of other males. It is possible that the mating plugs cannot be placed correctly or can shift when subadult females moult and thus may be a less effective barrier to remating. Additionally, the lack of somersaulting while mating with late subadult females may mechanically alter the insertion mechanism and affect where sperm is deposited within the female's reproductive tract. The location of deposited sperm and the storage conditions, together with potentially insufficient plugging in subadult matings, may yield lower reproductive success. In the congener, L. hasselti, the first of two males mating with an adult female achieves approximately 80% paternity (Snow & Andrade, 2005). However, the paternity share may differ if a subsequent male inseminates a female mated as subadult after she has moulted. These potential costs of mating with a subadult female can be revealed through paternity assessments in double-mating trials.
Our observation showed that L. geometricus males mate with late subadult females, but do not attempt to do so with younger subadults. Despite this, they did not show any preference for late over early subadult females. Cohabiting with subadult females and then mating with them when they moult is known for many spider species (Jackson, 1986) including the widow spiders (Biaggio et al., 2016, Segoli et al., 2006). Although in L. hasselti and L. geometricus the encounter with late subadult females often leads to immediate mating, cohabiting with early subadult females and waiting for them to mature may be another mating tactic in a male's repertoire. Additionally, it is likely that males cannot determine from a distance subadult females' readiness to mate.

Comparing learning to normative benchmarks reveals that people overreact to signals about goods that they own, but that learning is close to Bayesian for non-owned goods

Ownership, Learning, and Beliefs. Samuel M. Hartzmark Samuel Hirshmany Alex Imasz. November 2019.

Abstract: We examine how owning a good affects learning and beliefs about its quality. We show that people have more extreme reactions to information about a good that they own compared to the same information about a non-owned good: ownership causes more optimistic beliefs after receiving a positive signal and more pessimistic beliefs after receiving a negative signal. This effect on beliefs impacts the valuation gap between the minimum owners are willing to accept to part with the good and the maximum non-owners are willing to pay to attain it, i.e. the endowment effect. We show that the endowment effect increases in response to positive information and disappears with negative information. Comparing learning to normative benchmarks reveals that people overreact to signals about goods that they own, but that learning is close to Bayesian for non-owned goods. In exploring the mechanism, we find that ownership increases attention to recent signals about owned goods, exacerbating over-extrapolation. We demonstrate a similar relationship between ownership and over-extrapolation in survey data about stock market expectations. Our findings have implications for any setting with trade and scope for learning, and provide a microfoundation for models of disagreement that generate volume in asset markets.

KEYWORDS: biased beliefs, endowment effect, ownership, attention, behavioral economics, learning, extrapolation
JEL Classifications: D9, D12

American atheists are relatively liberal and likely to experience political conflict and follow political news; agnostics are particularly likely to vote and feel politically isolated from their families

The Politics of Religious Nones. Philip Schwadel. Journal for the Scientific Study of Religion, February 2 2020.

Abstract: Americans with no religious affiliation (aka religious “Nones”) are not a politically homogeneous community. Just as there are political differences between groups of Christians, there are political differences between groups of religious Nones. I use nationally representative survey data to examine the political activities and perspectives of atheists, agnostics, and those who are “nothing in particular.” Results show that Americans who report that their religion is nothing in particular are relatively uninterested in politics and unlikely to be politically active; atheists are relatively liberal and likely to experience political conflict and follow political news; and agnostics are particularly likely to vote and feel politically isolated from their families. In many ways, the “softer” secularism of those who are nothing in particular is politically more similar to religious affiliates than the “harder” secularism of agnostics and especially atheists. These results have important implications for the future of American politics as Nones now have the potential to rival evangelical Protestants as a politically relevant constituency.

The data used for this study come from Wave 23 of the Pew Research Center's American Trends Panel. The data can be downloaded from the Pew Research Center website:

Exposure to half-dressed women and economic behavior: Men take more risk, no effect on willingness to compete & math performance; very little effect on economic decision making

Exposure to half-dressed women and economic behavior. Evelina Bonnier et al. Journal of Economic Behavior & Organization, Volume 168, December 2019, Pages 393-418.

•    We randomize 648 participants of both genders in the lab to advertising images.
•    The images contain either half-dressed women, fully dressed women, or no women.
•    We study the effects on risk taking, willingness to compete and math performance.
•    We find no treatment effects on any outcome measure for women.
•    There is some evidence of men taking more risk after viewing half-dressed women.

Abstract: Images of half-dressed women are ubiquitous in advertising and popular culture. Yet little is known about the potential impacts of such images on economic decision making. We randomize 648 participants of both genders to advertising images including either women in bikini or underwear, fully dressed women, or no women, and examine the effects on risk taking, willingness to compete and math performance in a lab experiment. We find no treatment effects on any outcome measure for women. For men, our results indicate that men take more risk after having been exposed to images of half-dressed women compared to no women.

A sales tax is better at promoting healthy diets than the fat tax (a tax on "unhealthy" food) and the thin subsidy (a subsidy on "healthy" food)

A sales tax is better at promoting healthy diets than the fat tax and the thin subsidy. Zarko Kalamov. Health Economics, 2020;1–14, DOI: 10.1002/hec.3987

Abstract: We analyze how a sales tax levied on all food products impacts the consumption of healthy food, unhealthy food, and obesity. The sales tax can stimulate the consumption of healthy meals by lowering the time costs of food preparation. Moreover, the sales tax lowers obesity under more general conditions than a tax on unhealthy food (fat tax) and a subsidy on healthy food (thin subsidy). We calibrate the model using recent consumption and time use data from the US. The thin subsidy is counterproductive and increases weight. While both the sales tax and the fat tax mitigate obesity, the former imposes a lower excess burden on consumers.

Keywords: fat tax, obesity, sales tax, thin subsidy
JEL: D11; I12; I18; H31; H51

Many countries tax unhealthy foods to address the obesity epidemic: Chile, France, Ireland, Mexico, and the UK among others tax sugar-sweetened beverages (SSBs), Finland taxes sweets and non-alcoholic beverages, while Hungary taxes food products with health risks. However, these policies may be ineffective or even counterproductive in reducing obesity, as consumers may substitute to untaxed unhealthy food alternatives (Schroeter, Lusk, & Tyner, 2008). To minimize this problem, governments can broaden the tax base (Finkelstein, Zhen, Nonnemaker, & Todd, 2010; Harding & Lovenheim, 2017; Miao, Beghin, & Jensen, 2013). Therefore, nutrient taxes (such as a sugar tax or a fat tax) are more effective than product taxes (such as a tax on SSBs). This article is the first to propose a sales tax on all food products as an instrument that promotes healthy diets. A sales tax may stimulate healthy consumption by lowering the opportunity cost of cooking time. Moreover, a sales tax imposes a low excess burden on consumers, measured both per kcal reduction in consumption and per dollar of tax revenues. We model a representative consumer in a model akin to that of Yaniv, Rosin, and Tobol (2009) and take explicitly into account the higher opportunity cost in terms of time of healthy consumption. The individual chooses between consumption of healthy and unhealthy food and has a fixed out-of-work time constraint, which she can spend on cooking meals and leisure. The individual consumes unhealthy meals away-from-home (defined as food prepared away-from-home), and their preparation is not time-consuming. Healthy food is produced at home using both time and ingredients.

We show that the sales tax lowers the opportunity cost of time in food preparation and may thus stimulate healthy consumption. If the elasticity of substitution between healthy and unhealthy food is sufficiently high, the sales tax exerts a positive effect on the demand for healthy meals. A tax on unhealthy foods (called for simplicity a fat tax) and a subsidy to healthy consumption (called a thin subsidy) have qualitatively similar effects on the demand for healthy and unhealthy food. Moreover, we show that the policy, which reduces obesity under the least restrictive conditions, is a positive sales tax in the absence of a fat tax and a thin subsidy.
Our model builds on the empirical observation that home-cooked meals are healthier than away-from-home food. Compared to the consumption of away-from-home meals, intake of home-cooked food is associated with higher intake of fiber, iron, and calcium; lower intake of fat, sodium, and cholesterol; lower calorie density (Guthrie, Lin, & Frazao, 2002; Lin & Frazao, 1997; Lin & Frazao, 1999) and lower weight (Chou, Grossman, & Saffer, 2004; French, Harnack, & Jeffery, 2000). Furthermore, a higher frequency of food preparation raises the consumption of fruits and vegetables and lowers the intake of fat, SSBs and fast-food (Larson, Perry, Story, & Neumark-Sztainer, 2006; Laska, Larson, Neumark-Sztainer, & Story, 2012; McLaughlin, Tarasuk, & Kreiger, 2003; Monsivais, Aggarwal, & Drewnowski, 2014; Wolfson & Bleich, 2015b). The positive dietary impact of frequent cooking occurs irrespectively of the weight-loss intentions of individuals (Wolfson & Bleich, 2015a). Kolodinsky and Goldstein (2011) estimate that ten additional minutes of cooking time lower BMI by 0.13 points. Zick, Stevens, and Bryant (2011) find that ten minutes food preparation lower the BMI of women by 0.17 points and do not affect the BMI of men, who, however, are a small share of the meal preparers in their data.

In Section 4, we calibrate the model according to recent U.S. consumption and time allocation data. We estimate the home production function, the dietary characteristics of at-home- and away-from-home-food and the time allocation decisions such that they match data from the National Health and Nutrition Examination Survey (NHANES) 2009-2010 (CDC, 2010) and the American Time Use Survey (ATUS) 2010 (BLS, 2010). The simulated model makes predictions regarding the own- and cross-price elasticities of healthy and unhealthy food that match existing empirical data on these elasticities.

We find in the benchmark case of our simulation that a 10% sales tax lowers away-from-home consumption of men and women by 7.9% and 4.8%, respectively. On the other hand, men's at-home consumption declines by just 0.01% and that of women rises by 0.01%. Hence, the intake of at-home food remains almost unaffected. As a result, men lose 4% of their weight and women 1.8%. On the other hand, a 10% fat tax induces a stronger substitution of at-home for away-from-home consumption. Consequently, it leads to a lower weight decrease. Moreover, the excess burden of the sales tax, measured using the compensating variation, is lower than that of the fat tax, irrespective of whether we calculate the excess burden as the welfare loss per dollar of tax revenues or per reduction in calorie intake. Furthermore, the sales tax's excess burden is also small in absolute value. It equals around 1 − 1.7 cents per dollar of tax revenues and 2 − 2.9 cents per 100 kcal reduction in consumption. Lastly, an introduction of a thin subsidy stimulates strong substitution of healthy for unhealthy food, such that weight slightly increases following the subsidy's implementation. The article from Yaniv et al. (2009) is most related to our paper. They analyze the fat tax and thin subsidy under consideration of the time costs of home-food preparation. Neither policy instrument is unambiguously obesity-reducing because of indeterminate substitution effects on away-from-home food consumption and physical activity.

Bishai (2015) considers the welfare implications of a tax plus subsidy system that raises (lowers) the price of unhealthy (healthy) nutrients but leaves the final product prices unchanged. He shows that such a system may improve welfare.

There is strong empirical evidence that a fat tax does not necessarily reduce weight, because of a possible switch to untaxed alternatives (Chouinard, Davis, LaFrance, & Perloff, 2007; Fletcher, Frisvold, & Tefft, 2010b; Schroeter et al., 2008; Zhen, Finkelstein, Nonnemaker, Karns, & Todd, 2014). Schroeter et al. (2008) estimate that a tax on food-away-from-home and a subsidy on fruit and vegetables may increase obesity. Zhen et al. (2014) show that a tax on SSBs can reduce their consumption at the cost of higher intake of fat and sodium. Furthermore, Fletcher, Frisvold, and Tefft (2010a), Fletcher et al. (2010b) find empirical support that such taxes have a significant effect on SSB consumption, but an insignificant effect on weight. Jeffery, French, Raether, and Baxter (1994) and French et al. (1997) find a significant short-term impact of subsidizing fruits and salads at university and high school cafeteria, which vanishes after the removal of the subsidy. [...]


This paper has compared three different policy instruments, which can be used to address the problem of rising obesity levels: a fat tax (levied on food-away-from-home), a thin subsidy (levied on groceries that enter home food preparation) and a sales tax on all food items. First, we show that a sales tax may stimulate time-intensive healthy consumption by lowering the opportunity cost of time spent on food preparation. Therefore, it may exert a positive effect on the demand for healthy meals. If healthy and unhealthy meals are perfect substitutes, then all three policy instruments have the same qualitative impact on the consumer's demand: they reduce the consumption of unhealthy meals and raise the consumption of healthy food. Second, the policy which reduces obesity under the most general conditions is a sales tax in the absence of the fat tax and the thin subsidy.

A calibration of the model shows that the sales tax mitigates obesity at the lowest welfare cost for consumers. Furthermore, the deadweight cost of the sales tax is small is absolute value. It imposes an excess burden of less than 2 cents per dollar of tax revenues and 3 cents per 100 kcal reduction in the calorie-intake.

Our results open ample opportunities for future research. While this article extends the model of Yaniv et al. (2009) to include a general elasticity of substitution between food at-home and away-from-home and the possibility of non-food purchases, we do not consider the choice of physical exercise. Including it may produce further interesting results on the effects of a sales tax.

Additionally, this article hightlights the role of the price of time in consumption choices. It explains the higher time spent cooking by women through lower opportunity cost of leisure. Gender differences in the price of time are likely caused by the gender wage gap, as documented by Zick et al. (2011). These authors use wage regressions from the March Supplement of the Current Population Survey (CPS) and find the opportunity cost of time for men and women to be 20.57 $∕hour and 16.84 $∕hour, respectively. The gender wage gap is also likely to contribute to unequal distribution of cooking time in non single-adult households. Moreover, closing of the gap is likely to affect this distribution. Hence, more research is necessary to analyze how different opportunity costs of time and the elimination of these differences may affect household production.

Moreover, future work should compare the sales tax to nutrient-specific taxes such as a tax on sugar or fat content. The sales tax may be more efficient in promoting healthy diets as it targets several unhealthy nutrients at once by lowering away-from-home consumption. Furthermore, a comparison to the tax plus subsidy system of Bishai (2015) along the same lines is necessary.

This paper has contributed to the literature by emphasizing the time costs of healthy consumption and showing their importance for the optimal policy design. Future research should focus on analyzing other policies that lower the opportunity cost of home food preparation or provide other incentives for cooking. Two public health programs that have already been implemented in the US are the Supplemental Nutrition Assistance Program (SNAP) Healthy Incentives Pilot which provides financial incentives for the purchase of fruits and vegetables and the Women, Infants, and Children (WIC) Farmer's Market Nutrition program which issues coupons to participants to buy foods from farmers (Smith, Ng, & Popkin, 2013). An evaluation of the effects of these programs on the participants' cooking habits is an important research agenda.

Taxing all food products may be regressive, as poor households spend a larger proportion of their income on food relative to rich households. As a result, an important agenda for future research is to quantify this effect and analyze how governments should spend the tax receipts, such that the tax becomes less regressive. Additionally, it is well-known that a fat tax is also regressive (see, e.g., Chouinard et al. (2007)). Therefore, future work should compare the regressivity of a fat tax to that of a sales tax.