Archive for the ‘Proceedings of the National Academy of Sciences’ Category

Land, irrigation water, greenhouse gas, and reactive nitrogen burdens of meat, eggs, and dairy production in the United States

July 23, 2014 Comments off

Land, irrigation water, greenhouse gas, and reactive nitrogen burdens of meat, eggs, and dairy production in the United States
Source: Proceedings of the National Academy of Sciences

Livestock-based food production is an important and pervasive way humans impact the environment. It causes about one-fifth of global greenhouse gas emissions, and is the key land user and source of water pollution by nutrient overabundance. It also competes with biodiversity, and promotes species extinctions. Empowering consumers to make choices that mitigate some of these impacts through devising and disseminating numerically sound information is thus a key socioenvironmental priority. Unfortunately, currently available knowledge is incomplete and hampered by reliance on divergent methodologies that afford no general comparison of relative impacts of animal-based products. To overcome these hurdles, we introduce a methodology that facilitates such a comparison. We show that minimizing beef consumption mitigates the environmental costs of diet most effectively.

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Nonlinear permanent migration response to climatic variations but minimal response to disasters

July 3, 2014 Comments off

Nonlinear permanent migration response to climatic variations but minimal response to disasters
Source: Proceedings of the National Academy of Sciences

We present a microlevel study to simultaneously investigate the effects of variations in temperature and precipitation along with sudden natural disasters to infer their relative influence on migration that is likely permanent. The study is made possible by the availability of household panel data from Indonesia with an exceptional tracking rate combined with frequent occurrence of natural disasters and significant climatic variations, thus providing a quasi-experiment to examine the influence of environment on migration. Using data on 7,185 households followed over 15 y, we analyze whole-household, province-to-province migration, which allows us to understand the effects of environmental factors on permanent moves that may differ from temporary migration. The results suggest that permanent migration is influenced by climatic variations, whereas episodic disasters tend to have much smaller or no impact on such migration. In particular, temperature has a nonlinear effect on migration such that above 25 °C, a rise in temperature is related to an increase in outmigration, potentially through its impact on economic conditions. We use these results to estimate the impact of projected temperature increases on future permanent migration. Though precipitation also has a similar nonlinear effect on migration, the effect is smaller than that of temperature, underscoring the importance of using an expanded set of climatic factors as predictors of migration. These findings on the minimal influence of natural disasters and precipitation on permanent moves supplement previous findings on the significant role of these variables in promoting temporary migration.

See: With climate change, heat more than natural disasters will drive people away (EurekAlert!)

Experimental evidence of massive-scale emotional contagion through social networks

July 1, 2014 Comments off

Experimental evidence of massive-scale emotional contagion through social networks
Source: Proceedings of the National Academy of Sciences

Emotional states can be transferred to others via emotional contagion, leading people to experience the same emotions without their awareness. Emotional contagion is well established in laboratory experiments, with people transferring positive and negative emotions to others. Data from a large real-world social network, collected over a 20-y period suggests that longer-lasting moods (e.g., depression, happiness) can be transferred through networks [Fowler JH, Christakis NA (2008) BMJ 337:a2338], although the results are controversial. In an experiment with people who use Facebook, we test whether emotional contagion occurs outside of in-person interaction between individuals by reducing the amount of emotional content in the News Feed. When positive expressions were reduced, people produced fewer positive posts and more negative posts; when negative expressions were reduced, the opposite pattern occurred. These results indicate that emotions expressed by others on Facebook influence our own emotions, constituting experimental evidence for massive-scale contagion via social networks. This work also suggests that, in contrast to prevailing assumptions, in-person interaction and nonverbal cues are not strictly necessary for emotional contagion, and that the observation of others’ positive experiences constitutes a positive experience for people.

Economic scarcity alters the perception of race

June 26, 2014 Comments off

Economic scarcity alters the perception of race (PDF)
Source: Proceedings of the National Academy of Sciences

When the economy declines, racial minorities are hit the hardest. Although existing explanations for this effect focus on institutional causes, recent psychological findings suggest that scarcity may also alter perceptions of race in ways that exacerbate discrimination. We tested the hypothesis that economic resource scarcity causes decision makers to perceive African Americans as “Blacker” and that this visual distortion elicits disparities in the allocation of resources. Studies 1 and 2 demonstrated that scarcity altered perceptions of race, lowering subjects’ psychophysical threshold for seeing a mixed-race face as “Black” as opposed to “White.” In studies 3 and 4, scarcity led subjects to visualize African American faces as darker and more “stereotypically Black,” compared with a control condition. When presented to naïve subjects, face representations produced under scarcity elicited smaller allocations than control-condition representations. Together, these findings introduce a novel perceptual account for the proliferation of racial disparities under economic scarcity.

Father’s brain is sensitive to childcare experiences

June 19, 2014 Comments off

Father’s brain is sensitive to childcare experiences
Source: Proceedings of the National Academy of Sciences

Brain, oxytocin, and parenting behavior were measured in primary-caregiving mothers, secondary-caregiving fathers, and primary-caregiving homosexual fathers raising infants without maternal involvement. Parenting integrated functioning of two neural networks: subcortical-paralimbic structures implicated in emotional processing and cortical circuits involved in social understanding. Mothers showed greater activation in the emotional processing network and fathers in the socio-cognitive circuits, which were differentially linked with oxytocin and behavior. Primary-caregiving fathers exhibited high amygdala activation similar to mothers, alongside high superior temporal sulcus (STS) activation comparable to fathers, and functional connectivity between amygdala and STS. Among all fathers, time spent in childcare correlated with amygdala-STS connectivity. Findings describe mechanisms of brain malleability with caregiving experiences in human fathers.

Rate of false conviction of criminal defendants who are sentenced to death

May 7, 2014 Comments off

Rate of false conviction of criminal defendants who are sentenced to death (PDF)
Source: Proceedings of the National Academy of Sciences

The rate of erroneous conviction of innocent criminal defendants is often described as not merely unknown but unknowable. There is no systematic method to determine the accuracy of a criminal conviction; if there were, these errors would not occur in the first place. As a result, very few false convictions are ever discovered, and those that are discovered are not representative of the group as a whole. In the United States, however, a high proportion of false convictions that do come to light and produce exonerations are concentrated among the tiny minority of cases in which defendants are sentenced to death. This makes it possible to use data on death row exonerations to estimate the overall rate of false conviction among death sentences. The high rate of exoneration among death-sentenced defendants appears to be driven by the threat of execution, but most death-sentenced defendants are removed from death row and resentenced to life imprisonment, after which the likelihood of exoneration drops sharply. We use survival analysis to model this effect, and estimate that if all death-sentenced defendants remained under sentence of death indefinitely, at least 4.1% would be exonerated. We conclude that this is a conservative estimate of the proportion of false conviction among death sentences in the United States.

Changing the academic culture: Valuing patents and commercialization toward tenure and career advancement

May 2, 2014 Comments off

Changing the academic culture: Valuing patents and commercialization toward tenure and career advancement (PDF)
Source: Proceedings of the National Academy of Sciences

There is national and international recognition of the importance of innovation, technology transfer, and entrepreneurship for sustained economic revival. With the decline of industrial research laboratories in the United States, research universities are being asked to play a central role in our knowledge-centered economy by the technology transfer of their discoveries, innovations, and inventions. In response to this challenge, innovation ecologies at and around universities are starting to change. However, the change has been slow and limited. The authors believe this can be attributed partially to a lack of change in incentives for the central stakeholder, the faculty member. The authors have taken the position that universities should expand their criteria to treat patents, licensing, and commercialization activity by faculty as an important consideration for merit, tenure, and career advancement, along with publishing, teaching, and service. This position is placed in a historical context with a look at the history of tenure in the United States, patents, and licensing at universities, the current status of university tenure and career advancement processes, and models for the future.


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