Now that various countries are or will soon be moving towards relaxing shelter-in-place rules, it is important that people use a face covering, to avoid an exponential resurgence of the spreading of the coronavirus disease (COVID-19). Adherence to this measure will be made explicitly compulsory in many places. However, since it is impossible to control each and every person in a country, it is important to complement governmental laws with behavioral interventions devised to impact people’s behavior beyond the force of law. Here we report a pre-registered online experiment (N=2,459) using a heterogenous, although not representative, sample of people living in the USA, where we test the relative effect of messages highlighting that the coronavirus is a threat to “you” vs “your family” vs “your community” vs “your country” on self-reported intentions to wear a face covering. Results show that focusing on “your community” promotes intentions to wear a face covering relative to the baseline; the trend is the same when comparing “your community” to the other conditions, but not significant. We also conducted pre-registered analyses of gender differences on intentions to wear a face covering. We find that men less than women intend to wear a face covering, but this difference almost disappears in counties where wearing a face covering is mandatory. We also find that men less than women believe that they will be seriously affected by the coronavirus, and this partly mediates gender differences in intentions to wear a face covering (this is particularly ironic because official statistics actually show that men are affected by the COVID-19 more seriously than women). Finally, we also find gender differences in self-reported negative emotions felt when wearing a face covering. Men more than women agree that wearing a face covering is shameful, not cool, a sign of weakness, and a stigma; and these gender differences also mediate gender differences in intentions to wear a face covering.

Are humans intuitively altruistic, or does altruism require self-control? A theory of social heuristics, whereby intuitive responses favor typically successful behaviors, suggests that the answer may depend on who you are. In particular, evidence suggests that women are expected to behave altruistically, and are punished for failing to be altruistic, to a much greater extent than men. Thus, women (but not men) may internalize altruism as their intuitive response. Indeed, a meta-analysis of 13 new experiments and 9 experiments from other groups found that promoting intuition relative to deliberation increased giving in a Dictator Game among women, but not among men (Study 1, N = 4,366). Furthermore, this effect was shown to be moderated by explicit sex role identification (Study 2, N = 1,831): the more women described themselves using traditionally masculine attributes (e.g., dominance, independence) relative to traditionally feminine attributes (e.g., warmth, tenderness), the more deliberation reduced their altruism. Our findings shed light on the connection between gender and altruism, and highlight the importance of social heuristics in human prosociality.

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This paper lays the foundations of a combinatorial homotopy theory, called A-theory, for simplicial complexes, which reflects their connectivity properties. A collection of bigraded groups is constructed, and methods for computation are given. A Seifert-Van Kampen type theorem and a long exact sequence of relative A-groups are derived. A related theory for graphs is constructed as well. This theory provides a general framework encompassing homotopy methods used to prove connectivity results about buildings, graphs, and matroids.

Background Mitochondria are eukaryotic organelles responsible for energy production. Quantitative changes in human mitochondrial DNA (mtDNA) copy number have been implicated in various cancer types. Data from prospective cohort studies on mtDNA copy number and colorectal cancer risk have been lacking. Methods We evaluated the association between mtDNA copy number in peripheral blood and colorectal cancer risk in a nested case-control study of 422 colorectal cancer cases (168 cases with pre-diagnostic blood and 254 cases with post-diagnostic blood) and 874 controls who were free of colorectal cancer among participants of the Singapore Chinese Health Study. The relative mtDNA copy number was measured using real time PCR. Unconditional logistic regression methods were employed to examine the association between mtDNA copy number and colorectal cancer risk. Results There was a U-shaped relationship between the relative mtDNA copy number and colorectal cancer risk. Compared with the 2nd quartile, the odds ratios (95% confidence intervals) for subjects in the lowest and highest quartiles of relative mtDNA copy numbers were 1.81 (1.13–2.89) and 3.40 (2.15–5.36), respectively (Pcurvilinearity <0.0001). This U-shaped relationship was present in both men and women, similar for colon cancer and rectal cancer, and independent of the timing of blood draw with regards to cancer diagnosis. Conclusions This is the first prospectively designed study to show a U-shaped association between the relative mtDNA copy number and risk of colorectal cancer. Impact The findings of the present study support that mtDNA may play a critical role in the colorectal carcinogenesis in humans.