People generally only engage in reciprocal generosity with others of equal or unknown status, MIT researchers experimentally demonstrated. During repeated interactions between people of different social status, generosity typically flows only one way, either up or down.

Using 20 years of satellite-derived data on wildfire severity and smoke particulate matter from California, Iván Higuera-Mendieta and Marshall Burke conclude that low-severity fires – a proxy for prescribed burns – can significantly reduce the probability of very high severity wildfires for a decade. The smoke particulate pollution produced by these less severe fires is outweighed by the reductions in future smoke from wildfires as a result. The researchers’ modeling suggests that sustained treatment of 500,000 acres annually in California with prescribed burns would reduce cumulative harmful smoke pollution by about 10% over a decade. The findings by Higuera-Mendieta and Burke fill an important data gap about potential air quality tradeoffs associated with prescribed burns. The effects measured in the study are most impactful in the state’s conifer forests, the researchers found. A policy that applies prescribed burning for up to 1 million acres/year in California conifer forests would yield cumulative benefits in terms of smoke reduction that exceed the costs of the added smoke from the initial prescribed burning “in as early as two years, with benefits exceeding costs by at least three-fold a decade after project initiation,” the authors write.

A new study suggests that variables linked to socioeconomic status (SES) – such as increased stress and reduced sleep – have strong relationships to brain structure and function in children. “Although previous work has found that socioeconomics can affect brain structure and function, [these authors] demonstrate these effects with notable scale and consistency,” write Lucinda M. Sisk and Theodore D. Satterthwaite in a related Perspective. Brain-wide association studies (BWAS) examine how variability in brain structure or function across many people relates to differences in behavior, mental health, or environmental exposures. Such studies often evaluate brain measures such as functional connectivity and cortical thickness, which vary in individuals and can change over time. Here, Scott Marek et al. sought to identify which exposures (from 649 different variables) were most strongly associated with functional connectivity and cortical thickness in a sample of youth aged 9 to 10 from the Adolescent Brain Cognitive Development (ABCD) Study.

 

The authors found that a composite of factors related to SES – like family income and neighborhood opportunity – were most strongly associated with functional connectivity. Such SES-associated differences in functional connectivity were strongest in brain regions involved in sensory and motor processing, where screen time and reduced sleep – both linked to lower socioeconomic status – showed strongest associations. Because these brain regions are related to arousal, and because arousal operates as a regulator of brain activity, it is possible socioeconomic status–related stressors may alter arousal patterns over time, producing lasting differences in brain function, say the authors. Marek and colleagues saw the same patterns when they replicated their study in a sample from the UK Biobank (95% white British, white Irish, or other white background). Combined with analyses stratified by genetic ancestry in the original youth sample, these findings indicate that the brain differences associated with socioeconomic factors are unrelated to genetic ancestry, say the authors. Marek and colleagues note that it “remains unclear when strong associations between the brain and SES first emerge or when environmental interventions may be most beneficial,” but “socioeconomic opportunity is not destiny." Any patterns established during sensitive periods of growth may not be permanent. Leading candidates for bolstering brain function and structure may be interventions related to sleep and chronic stress. The findings highlight the need for societal-level policies that provide early support for families, say Sisk and Satterthwaite in the Perspective.

 

 

Podcast: A segment of Science's weekly podcast with Scott Marek, related to this research, will be available on the Science.org podcast landing page after the embargo lifts. Reporters are free to make use of the segments for broadcast purposes and/or quote from them – with appropriate attribution (i.e., cite "Science podcast"). Please note that the file itself should not be posted to any other Web site.

A new study finds that employer points systems, which penalize workers for absences regardless of the reason, are strongly associated with presenteeism, the practice of showing up to work while sick, and that these systems undermine the public health benefits of paid sick leave laws even in jurisdictions where such protections are on the books.

How can universities and colleges make the process of granting promotions and tenure to faculty members fairer, more equitable, and more transparent? The Center for Excellence in Faculty Advancement presents a framework that all institutions can follow.

From insects to great apes, by way of birds and fish, animals communicate through an extraordinary variety of sounds. Whilst the pitch or timbre of their vocalisations matters, rhythm may play a more fundamental role. Scientists from the University of Geneva (UNIGE), the NCCR Evolving Language, the reConnect Institute and the Institut Pasteur analysed more than 2,000 sound recordings produced by 98 animal species. All of them vocalise at a strikingly similar rate — roughly two to three acoustic events per second — regardless of their size, habitat, species or social complexity. This constraint is likely linked to the brain’s capacity to process auditory stimuli, and human language is no exception. The findings are published in PLOS Biology.

Adolescents who spend at least two hours a day on social media are more likely to experience depressive symptoms and poorer wellbeing, with the strongest effects in early adolescence, according to new research.