PNAS nexus最新文献

A fundamental feature for understanding the diffusion of innovations through a social group is the manner in which we are influenced by our own social interactions. It is usually assumed that only direct interactions, those that form our social network, determine the dynamics of adopting innovations. Here, we test this assumption by experimentally and theoretically studying the role of direct and indirect influences in the adoption of innovations. We perform experiments specifically designed to capture the influence that an individual receives from their direct social ties as well as from those socially close to them, as a function of the separation they have in their social network. The results of 21 experimental sessions with more than 590 participants show that the rate of adoption of an innovation is significantly influenced not only by our nearest neighbors but also by the second and third levels of influences an adopter has. Using a mathematical model that accounts for both direct and indirect interactions in a network, we fit the experimental results and determine the way in which influences decay with social distance. The results indicate that the strength of peer pressure on an adopter coming from its second and third circles of influence is approximately two-third and one-third, respectively, relative to their closest neighbors. Our results strongly suggest that the adoption of an innovation is a complex process in which an individual feels significant pressure not only from their direct ties but also by those socially close to them.

The rise of generative AI tools has sparked debates about the labeling of AI-generated content. Yet, the impact of such labels remains uncertain. In two preregistered online experiments among US and UK participants (N = 4,976), we show that while participants did not equate "AI-generated" with "False," labeling headlines as AI-generated lowered their perceived accuracy and participants' willingness to share them, regardless of whether the headlines were true or false, and created by humans or AI. The impact of labeling headlines as AI-generated was three times smaller than labeling them as false. This AI aversion is due to expectations that headlines labeled as AI-generated have been entirely written by AI with no human supervision. These findings suggest that the labeling of AI-generated content should be approached cautiously to avoid unintended negative effects on harmless or even beneficial AI-generated content and that effective deployment of labels requires transparency regarding their meaning.

Sea level rise and climate change are shaping present societies, particularly those on oceanic islands. Few historical examples could serve as references for these changes. One such potential model is the Saudeleur Dynasty with its capital Nan Madol on the Pacific Island of Pohnpei. However, the timing of its construction, as well as the dynasty's fluctuations and potential environmental influences, has remained unresolved. Through the analyses of ²³⁰Th ages on 171 dates on corals fragments used as building materials and charcoal ¹⁴C ages from excavations, 2 major construction phases spanning from the 10th to the 15th century CE can be discerned. The results show that the first phase of the site's construction, spanning the 10th-12th century, marked the dynasty's rise. The second period, spanning from the late 12th to the early 15th century, provides the most substantial evidence for the demise of the island-scale chiefdom and a significant societal reorganization. The phases are centuries earlier than previously believed. With this new evidence, we propose the hypothesis that variations in the El Niño-Southern Oscillation and subsidence-related sea level rise presented major challenges for building and maintaining Nan Madol, and thus, influenced the course of the island's history. This case serves as a compelling example of how adverse climatic conditions can spur investments-in this case, in seawater defense under high sea levels-yet ultimately may contribute to abandonment. It offers lessons for island nations, showcasing coastal resilience in the face of worsening catastrophic events that unfolded over generations.

Influenza virus seasonality, synchronicity, and vaccine supply differ substantially between temperate and tropical settings, and optimal vaccination strategy may differ on this basis. Many national vaccine recommendations focus on high-risk groups, elderly populations, and healthcare workers despite previous analyses demonstrating broad benefits to vaccinating younger high-contact age groups. In this study, we parameterized an age-structured nonseasonal asynchronous epidemiological model of influenza virus transmission for a tropical low-income setting. We evaluated timing and age allocation of vaccines across vaccine supplies ranging from 10 to 90% using decade-based age groups. Year-round vaccination was beneficial when compared with more concentrated annual vaccine distribution. When targeting a single age group for vaccine prioritization, maximum vaccine allocation to the 10-19 high-contact age group minimized annual influenza mortality for all but one vaccine supply. When evaluating across all possible age allocations, optimal strategies always allocated a plurality of vaccines to school-age children (10-19). The converse, however, was not true as not all strategies allocating a plurality to children aged 10-19 minimized mortality. Allocating a high proportion of vaccine supply to the 10-19 age group is necessary but not sufficient to minimize annual mortality as distribution of remaining vaccine doses to other age groups also needs to be optimized. Strategies focusing on indirect benefits (vaccinating children) showed higher variance in mortality outcomes than strategies focusing on direct benefits (vaccinating the elderly). However, the indirect benefit approaches showed a lower mean mortality and a lower minimum mortality than vaccination focused on the elderly.

In this article, we test and compare several message-based nudges designed to promote civil discourse and reduce the circulation of harmful content such as hate speech. We conducted a large pre-registered experiment (N = 4,081) to measure the effectiveness of seven nudges: making descriptive norms, injunctive norms, or personal norms salient, cooling down negative emotions, stimulating deliberation or empathy, and highlighting reputation. We used an online platform that reproduces a social media newsfeed and presented the nudge as a message when entering the platform. Our findings indicate that none of the nudges significantly impacts participants' engagement with harmful content. At the same time, nudges making descriptive norms salient selectively increase participants' overall engagement with relatively harmless content. Additionally, making injunctive norms salient increased the likelihood of liking harmless posts. Exploratory text analysis also reveals that highlighting reputation leads to more substantial and coherent comments on harmful posts. These results suggest that nudges that activate norm considerations represent a promising approach to promoting civil discourse and making social media a safer and more inclusive space for all.

We contribute to the public debate on immigration policy in the United States by providing a long-term, empirical perspective. We develop a novel method of linking individuals across historical Census waves to trace the lives of millions of immigrants in the past and compare their outcomes with immigrants today. We document that upward mobility is just as possible for immigrants today as it was in the early 20th century, and that children of immigrant parents catch up to and frequently exceed the economic outcomes of the children of US-born parents. By our measures, immigrants as a group are no more likely to be incarcerated than those born in the United States, and they assimilate into American culture today at rates comparable to historical standards. Attitudes toward immigrants today are more positive than a century ago, albeit more polarized by political party.

Rising surface temperatures are projected to cause more frequent and intense droughts in the world's drylands. This can lead to land degradation, mobilization of soil particles, and an increase in dust aerosol emissions from arid and semi-arid regions. Dust aerosols are a key source of bio-essential nutrients, can be transported in the atmosphere over large distances, and ultimately deposited onto the ocean's surface, alleviating nutrient limitation and increasing oceanic primary productivity. Currently, the linkages between desertification, dust emissions and ocean fertilization remain poorly understood. Here, we show that dust emitted from Southern Africa was transported and deposited into the nutrient-limited surface waters southeast of Madagascar, which stimulated the strongest phytoplankton bloom of the last two decades during a period of the year when blooms are not expected. The conditions required for triggering blooms of this magnitude are anomalous, but current trends in air temperatures, aridity, and dust emissions in Southern Africa suggest that such events could become more probable in the future. Together with the recent findings on ocean fertilization by drought-induced megafires in Australia, our results point toward a potential link between global warming, drought, aerosol emissions, and ocean blooms.

Impaired organelle-specific protein import triggers a variety of cellular stress responses, including adaptive pathways to balance protein homeostasis. Most of the previous studies focus on the cellular stress response triggered by misfolded proteins or defective protein import in the endoplasmic reticulum or mitochondria. However, little is known about the cellular stress response to impaired protein import in the peroxisome, an understudied organelle that has recently emerged as a key signaling hub for cellular and metabolic homeostasis. To uncover evolutionarily conserved cellular responses upon defective peroxisomal import, we carried out a comparative transcriptomic analysis on fruit flies with tissue-specific peroxin knockdown and human HEK293 cells expressing dominant-negative PEX5^C11A. Our RNA-seq results reveal that defective peroxisomal import upregulates integrated stress response (ISR) and downregulates ribosome biogenesis in both flies and human cells. Functional analyses confirm that impaired peroxisomal import induces eIF2α phosphorylation and ATF4 expression. Loss of ATF4 exaggerates cellular damage upon peroxisomal import defects, suggesting that ATF4 activation serves as a cellular cytoprotective mechanism upon peroxisomal import stress. Intriguingly, we show that peroxisomal import stress decreases the expression of rRNA processing genes and inhibits early pre-rRNA processing, which leads to the accumulation of 47S precursor rRNA and reduction of downstream rRNA intermediates. Taken together, we identify ISR activation and ribosome biogenesis inhibition as conserved adaptive stress responses to defective peroxisomal import and uncover a novel link between peroxisomal dysfunction and rRNA processing.

In holometabolous insects, proper control of the production of juvenile hormone (JH), which maintains larval traits, is crucial for successful metamorphosis. JH is produced specifically in the corpora allata (CA) via the functioning of a set of JH biosynthetic enzymes (JHBEs). Expression of JHBE genes in the CA is coordinated except for JH acid methyltransferase (JHAMT), which functions in the last step of JH biosynthesis. Here, we sought to determine the mechanism that enables this coordinated expression, assuming the presence of a central regulator of JHBE genes. Comparison of transcriptomes in the CA during active and inactive stages revealed the presence of 3 transcription factors, whose expression patterns matched those of JHBE genes. We propose that one of these, Dead ringer (Dri), is the central up-regulator of CA-specific JHBE genes including JHAMT, based on the following findings: (ⅰ) Knockdown of Dri in the larvae caused precocious metamorphosis, which was rescued by the exogenous application of JH analog, and (ⅱ) knockdown of Dri decreased the expression of most CA-specific JHBE genes examined. Furthermore, RNAi-based reverse genetics indicated that Dri works most upstream in the control of CA-specific JHBE genes, and that shutdown of JHAMT, which occurs independent of other JHBE genes prior to the onset of metamorphosis, can be hypothetically explained by the presence of an unidentified repressor. Our study suggests that Dri, which has been known to regulate embryonic development in a wide range of animals, is conferred a new role in holometabolous insects, i.e. central regulation of CA-specific JHBE genes.

One of humanity's greatest strengths lies in our ability to collaborate to achieve more than we can alone. Just as collaboration can be an important strength, humankind's inability to detect deception is one of our greatest weaknesses. Recently, our struggles with deception detection have been the subject of scholarly and public attention with the rise and spread of misinformation online, which threatens public health and civic society. Fortunately, prior work indicates that going beyond the individual can ameliorate weaknesses in deception detection by promoting active discussion or by harnessing the "wisdom of crowds." Can group collaboration similarly enhance our ability to recognize online misinformation? We conducted a lab experiment where participants assessed the veracity of credible news and misinformation on social media either as an actively collaborating group or while working alone. Our results suggest that collaborative groups were more accurate than individuals at detecting false posts, but not more accurate than a majority-based simulated group, suggesting that "wisdom of crowds" is the more efficient method for identifying misinformation. Our findings reorient research and policy from focusing on the individual to approaches that rely on crowdsourcing or potentially on collaboration in addressing the problem of misinformation.