Wednesday, October 25, 2017

Twin-killing in some traditional societies: An economic perspective

Twin-killing in some traditional societies: An economic perspective. Andrés Marroquín & Colleen Haight. Journal of Bioeconomics, October 2017, October 2017, Volume 19, Issue 3, pp 261–279.

Abstract: Historically, some societies around the world killed newborn twins, though the practice was forsaken in the early twentieth century. Anthropologists have proposed different theses: (1) the delivery of twins occurred when the mother cheated on her husband, or committed a great sin, and killing the twins was the penalty, (2) twin-killing was done to assert that human beings were different from animals among which multiple births in the same delivery were seen, (3) twins brought a dilemma to the kinship structure of societies and to cope with it different rules were adopted, twin-killing being the extreme one, (4) twin-killing was a means to face resource stress. We argue that although those interpretations are useful, we can improve the understanding of that phenomenon by adding an identity economics model, where twins are a taboo. Identity economics helps us explain the persistence of the practice and its eventual decline. We make our case with examples from the Igbo of Nigeria.

No evidence that preferences for facial masculinity track changes in women's hormonal status

No evidence that preferences for facial masculinity track changes in women's hormonal status. Benedict C. Jones, Amanda C. Hahn, Claire I. Fisher, Hongyi Wang, Michal Kandrik, Chengyang Han, Vanessa Fasolt, Danielle Morrison, Iris J. Holzleitner, Kieran J. O'Shea, Craig Roberts, Anthony C. Little, Lisa M. DeBruine. Available at bioRxiv 136549; doi:

Abstract: Although widely cited as strong evidence that sexual selection has shaped human facial attractiveness judgments, evidence that preferences for masculine characteristics in men's faces are related to women's hormonal status is equivocal and controversial. Consequently, we conducted the largest ever longitudinal study of the hormonal correlates of women's preferences for facial masculinity (N=584). Analyses showed no evidence that preferences for facial masculinity were related to changes in women's salivary steroid hormone levels. Furthermore, both within-subject and between-subject comparisons showed no evidence that oral contraceptive use decreased masculinity preferences. However, women generally preferred masculinized over feminized versions of men's faces, particularly when assessing men's attractiveness for short-term, rather than long-term, relationships. Our results do not support the hypothesized link between women's preferences for facial masculinity and their hormonal status.

More lumbar curvature increased perception of attractiveness of girls, men looked longer & fixated more on the hip region

Pazhoohi, F., Doyle, J.F., Macedo, A.F. et al. Evolutionary Psychological Science (2017).

Abstract: It is common in studies of human mate preference to have participants judge the attractiveness of photographs in which models adopt a neutral facial expression or a neutral body posture. However, it is unlikely that humans adopt neutral expressions and postures in normal social circumstances. One way in which posture can vary is in the curvature of the lower spine. In some non-human animals, a “lordotic” posture (in which the lower spine is curved towards the belly) is associated in females with readiness to mate. In humans, this posture may serve a similar function, attracting heterosexual men. In this study, participants were presented with computer-generated images of female bodies in which the back curvature was systematically manipulated. The result showed that small changes in lumbar curvature are associated with changes in the perception of attractiveness. Specifically, the result showed that there is a relationship between the range of the back curvatures used in this study and attractiveness, such that increasing the curvature increased the perception of attractiveness. Additionally, as the curvature increased, participants looked longer and fixated more on the hip region of the female bodies. This paper argues that the attractiveness of women in lordotic posture is due to a conserved mechanism across the taxa which signals proceptivity to men.

Check also: Behavioral display of lumbar curvature in response to the opposite sex. Zeynep Şenveli Bilkent University, Graduate Program in Neuroscience - Master's degree thesis.

Carl J. Armstrong Jr.'s comment on this >>> Counter-explanation: Lumbar curvature may be a critical factor in mobility during late pregnancy. Lordotic posture--demonstrating lumbar mobility--may signal healthy mobility during reproduction.

Likewise, given that spinal asymmetry drives breast asymmetry, breast fullness and symmetry may also indicate part of the same mobility-during-pregnancy by telegraphing spinal health and motility....

New evidence that ageing societies become more risk-averse

Global Evidence on Economic Preferences. Armin Falk, Anke Becker, Thomas Dohmen, Benjamin Enke, David B. Huffman, Uwe Sunde. NBER Working Paper No. 23943.

Abstract: This paper studies the global variation in economic preferences. For this purpose, we present the Global Preference Survey (GPS), an experimentally validated survey dataset of time preference, risk preference, positive and negative reciprocity, altruism, and trust from 80,000 individuals in 76 countries. The data reveal substantial heterogeneity in preferences across countries, but even larger within-country heterogeneity. Across individuals, preferences vary with age, gender, and cognitive ability, yet these relationships appear partly country specific. At the country level, the data reveal correlations between preferences and bio-geographic and cultural variables such as agricultural suitability, language structure, and religion. Variation in preferences is also correlated with economic outcomes and behaviors. Within countries and subnational regions, preferences are linked to individual savings decisions, labor market choices, and prosocial behaviors. Across countries, preferences vary with aggregate outcomes ranging from per capita income, to entrepreneurial activities, to the frequency of armed conflicts.

More than 50% or Less than 70% Chance: Pragmatic Implications of Single-Bound Probability Estimates

Hohle, S. M., and Teigen, K. H. (2017) More than 50% or Less than 70% Chance: Pragmatic Implications of Single-Bound Probability Estimates. J. Behav. Dec. Making, doi: 10.1002/bdm.2052

Abstract: Probability estimates can be given as ranges or uncertainty intervals, where often only one of the interval bounds (lower or upper) is specified. For instance, a climate forecast can describe La Niña as having “more than 70% chance” or “less than 90% chance” of occurring. In three experiments, we studied how research participants perceived climate-related forecasts expressed with lower-bound (“over X% chance”) or upper-bound (“under Y% chance”) probability statements. Results indicate that such single-bound statements give pragmatic information in addition to the numeric probabilities they convey. First, the studies show that these statements are directional, leading the listeners' attention in opposite directions. “Over” statements guide attention towards the possible occurrence of the event and are explained by reasons for why it might happen, while “under” statements direct attention to its possible non-occurrence and are more often explained by reasons for why the target event might not appear, corresponding to positive (it is possible) versus negative (it is uncertain) verbal probabilities. Second, boundaries were found to reveal the forecaster's beliefs and could be perceived as indicative of an increasing or a decreasing trend. Single-bound probability estimates are therefore not neutral communications of probability level but might “leak” information about the speaker's expectations and about past and future developments of the forecast.

In economics, 42% of papers that were published as replication studies successfully replicated another experiment

Maniadis, Z., Tufano, F. and List, J. A. (2017), To Replicate or Not To Replicate? Exploring Reproducibility in Economics through the Lens of a Model and a Pilot Study. Econ J, 127: F209–F235. doi:10.1111/ecoj.12527

Abstract: The sciences are in an era of an alleged ‘credibility crisis’. In this study, we discuss the reproducibility of empirical results, focusing on economics research. By combining theory and empirical evidence, we discuss the import of replication studies and whether they improve our confidence in novel findings. The theory sheds light on the importance of replications, even when replications are subject to bias. We then present a pilot meta-study of replication in experimental economics, a subfield serving as a positive benchmark for investigating the credibility of economics. Our meta-study highlights certain difficulties when applying meta-research to systematise the economics literature.

Concerning the replication results themselves, an interesting insight is that we found a ‘success rate’, based on 85 replications, of 42.3%. This means that roughly 40% of papers that were published as replication studies successfully replicated another experiment. This is somewhat higher than the outcome of the recent large-scale replication initiative from psychology (Open Science Collaboration, 2015) and Duvendack et al. (2015), which both found a success rate of about a third, while, also in psychology, Makel et al. (2012) found a very high success rate of 73%.

Small decline in overall narcissism, leadership, vanity & entitlement levels in college students from the 1990s to the 2010s

The Narcissism Epidemic Is Dead; Long Live the Narcissism Epidemic. Eunike Wetzel et al.
Psychological Science,

Abstract: Are recent cohorts of college students more narcissistic than their predecessors? To address debates about the so-called “narcissism epidemic,” we used data from three cohorts of students (1990s: N = 1,166; 2000s: N = 33,647; 2010s: N = 25,412) to test whether narcissism levels (overall and specific facets) have increased across generations. We also tested whether our measure, the Narcissistic Personality Inventory (NPI), showed measurement equivalence across the three cohorts, a critical analysis that had been overlooked in prior research. We found that several NPI items were not equivalent across cohorts. Models accounting for nonequivalence of these items indicated a small decline in overall narcissism levels from the 1990s to the 2010s (d = −0.27). At the facet level, leadership (d = −0.20), vanity (d = −0.16), and entitlement (d = −0.28) all showed decreases. Our results contradict the claim that recent cohorts of college students are more narcissistic than earlier generations of college students.

A glass of wine is spoilt by a single D. melanogaster fly falling into it

The scent of the fly. Paul G. Becher, Sebastien Lebreton, Erika A. Wallin, Erik Hedenstrom, Felipe Borrero-Echeverry, Marie Bengtsson, Volker Jorger, View ORCID ProfilePeter Witzgall. bioRxiv,

Abstract: (Z)-4-undecenal (Z4-11Al) is the volatile pheromone produced by females of the vinegar fly Drosophila melanogaster. Female flies emit Z4-11Al at few nanograms per hour, for species-specific communication and mate-finding. Tests with synthetic Z4-11Al show that it has a characteristic off-flavour, which we perceive even at the small amounts produced by one female fly. Since only females produce Z4-11Al, and not males, we can reliably distinguish between single D. melanogaster males and females, according to their scent. A wine-tasting panel finds that we sense as little as 1 ng synthetic Z4-11Al in a glass of wine, and 10 ng Z4-11Al is perceived as a loud off-flavour. This corroborates the observation that a glass of wine is spoilt by a single D. melanogaster fly falling into it, which we here show is caused by Z4-11Al. The biological role of Z4-11Al or structurally related aldehydes in humans and the basis for this semiochemical convergence remains yet unclear.