Displacement Hypothesis Research Articles

Screen time and moderate-to-vigorous physical activity changes and displacement in adolescence: A prospective cohort study

Background: This paper determines longitudinal changes in the time Spanish adolescents devote to moderate-to-vigorous physical activity (MVPA) and screen media activity (SMA). Moreover, it examines the displacement hypothesis between time spent on SMA and MVPA.Methods: A cohort of 755 adolescents participated in a prospective cohort study over a three-year period. Repeated measures ANOVA to highlight interaction effects among all variables and Structural Equation Modeling (SEM) techniques were employed.Results: Age and gender-related variations in longitudinal changes in time spent on MVPA and SMA evolved in the inverse direction (decreased on MVPA/increased on SMA) according to the ANOVA. The potential displacement between time spent on SMA and MVPA from Wave I to Wave II was analysed via SEM. The first model, estimated in the overall sample, showed no evidence for the displacement hypothesis. Subsequently, a multigroup sequence of panel models was performed and a partial displacement was observed only in boys. Hence, boys who spent more time on SMA were more likely to devote less time to MVPA three years later.Conclusion: This study confirms the opposite trend on the time spent on MVPA and SMA over a three-year period, being clearly higher in SMA. Further SEM analyses reveal a deferred displacement hypothesis between SMA and MVPA only in boys. This partial gendered displacement may be linked to the different uses adolescents make of screen media. The incursion of new technological devices (smartphones or tablets) and their wide range of possibilities for social networking or gaming could explain this displacement

Digital Screen Time and Pediatric Sleep: Evidence from a Preregistered Cohort Study

To determine the extent to which time spent with digital devices predicts meaningful variability in pediatric sleep. Following a preregistered analysis plan, data from a sample of American children (n = 50 212) derived from the 2016 National Survey of Children's Health were analyzed. Models adjusted for child-, caregiver-, household-, and community-level covariates to estimate the potential effects of digital screen use. Each hour devoted to digital screens was associated with 3-8 fewer minutes of nightly sleep and significantly lower levels of sleep consistency. Furthermore, those children who complied with 2010 and 2016 American Academy of Pediatrics guidance on screen time limits reported between 20 and 26 more minutes, respectively, of nightly sleep. However, links between digital screen time and pediatric sleep outcomes were modest, accounting for less than 1.9% of observed variability in sleep outcomes. Digital screen time, on its own, has little practical effect on pediatric sleep. Contextual factors surrounding screen time exert a more pronounced influence on pediatric sleep compared to screen time itself. These findings provide an empirically robust template for those investigating the digital displacement hypothesis as well as informing policy-making.

Young children's television viewing and the quality of their interactions with parents: A prospective community study.

Television is one of the most commonly viewed forms of media by children throughout the world. Excessive television viewing can influence the quality of children's relationships and interactions with their parents. We examined the emotional availability (EA) of children toward their parents by assessing child responsiveness and child involvement, using a cross-sectional and longitudinal design. We employed a large and representative community sample of Norwegian 4-year-olds (n = 995) who were followed up at 6 years old (n = 795). The results illustrate that, when viewing excessive amounts of television, children are less likely to be involved with their parents in ordinary toy-play. We argue in favor of the displacement hypothesis, stating that time-demanding technologies are negatively related to the quality of parent-child relationships because spending more time watching television will leave less time for developing nurturing social relationships.

Impact of Public Smoking Bans on Social Inequalities in Children's Exposure to Tobacco Smoke at Home: An Equity-Focused Systematic Review.

A systematic review was conducted to evaluate the impact of public smoking bans on social inequalities in children's secondhand smoke (SHS) exposure at home. Five databases were electronically searched for articles on children's SHS exposure at home related to public smoking bans. In addition, the gray literature and German public health journals were considered. Search was restricted to English and German publications. Of 3037 records screened, 25 studies fulfilled the inclusion criteria by either measuring SHS exposure before and after public smoking ban introduction or by comparing exposure between regions with and without smoke-free legislation. Studies were further examined whether they additionally reported on impacts on social inequalities in SHS exposure. Information on children's SHS exposure at home in relation to smoke-free legislation were extracted by one reviewer and checked for accuracy by a second reviewer. According to Preferred Reporting Items for Systematic Reviews and Meta-Analyses-Equity (PRISMA-E) guidelines for equity-focused systematic reviews, the PROGRESS-Plus framework was applied to data extraction and analysis with focus on social inequalities in SHS exposure. Results were visualized by a harvest plot. Eight studies gave results on the impact of public smoking bans on social inequalities in children's SHS exposure. Whereas only one study indicated widening of the social gap in exposure, seven studies showed no impact or a reduction of social inequalities in exposure. First evidence on short-term impact of public smoking bans does not support the assumption of intervention-generated inequalities in children's SHS exposure at home. Future studies should focus on long-term equity impacts of smoke-free legislation. There are substantial social inequalities in children's SHS exposure in many countries. Both hypotheses on the effect of smoke-free legislation on children's SHS exposure at home, the displacement hypothesis and the social diffusion hypothesis, did not take social inequalities into account. Up to now, only few studies analyzed the effects of smoke-free legislation on social inequalities in children's SHS exposure at home. Public smoking bans had overall no negative impact on social inequalities in children's SHS exposure at home. More consistent reporting of absolute and relative inequalities is needed to comprehensively assess equity impact of smoke-free legislation.

Two tests of social displacement through social media use

ABSTRACTThe present manuscript presents two tests of the hypothesis that social media use decreases social interaction, leading to decreased well-being. Study 1 used the Longitudinal Study of American Youth (N = 2774), which is a national probability sample of Generation X, to test displacement over a three-year time period. Latent change scores were used to test associations among social media adoption in 2009, social media use in 2011, direct contact frequency across years, in relation to change in well-being. Although social media adoption in 2009 predicted less social contact in 2011, increased social media use between 2009 and 2011 positively predicted well-being. Study 2 used experience sampling with a combined community and undergraduate sample (N = 116). Participants reported on their social interactions and passive social media use (i.e., excluding chat via social media) five times a day over five days. Results indicate that social media use at prior times of day was not associated with future social interaction with close others or with future face-to-face interaction. Passive social media use at prior times predicted lower future well-being only when alone at prior times. Neither study supported the social displacement hypothesis. Several interpretations of results, including a need-based account of social media use, are examined. The challenges of identifying an appropriate time scale to study social displacement are identified as critical question for future research.

Assessing the long-term causal effect of trout invasion on a native charr

Many studies have indicated that invasive species can drive declines in native species through interspecific competition. In freshwater ecosystems, brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) have been implicated in reducing native species, especially congeneric salmonid fishes. However, demonstrating causality in the wild is problematic because non-natives might replace natives in areas where the former were extirpated by other environmental changes. Using the recently developed technique of multispatial convergent cross mapping (CCM) and a long-term monitoring data set (2002–2017) with spatial replication on both introduced and native salmonids in a Japanese stream, I tested whether an increase in non-native trout caused a decrease in native charr (Salvelinus leucomaenis). Native charr decreased their population density over time in contrast to the non-native brown trout and rainbow trout. The dominant species changed from native charr (64%) in 2002 to non-native trout (97%) by 2017. Multispatial CCM identified significant causal forcing of the native charr by both rainbow trout and brown trout, lending support for the hypothesis of displacement, rather than replacement, of a native species by non-native species. These results therefore suggest that eradicating the invasive trout species may aid the recovery of native charr in the region.

Failure analysis of masonry arch with no-horizontal support settlement

In this paper, the Principle of Virtual Work was applied to evaluate the collapse mechanism shape, the support reaction forces and the thrust line of masonry arch with no-horizontal springing settlement. Considering the hypothesis of finite displacement, an iterative algorithm was performed with the aim to describe the arch mechanism at every step of imposed springing settlement. In addition, the ultimate displacement causing the complete failure of masonry arch with no-horizontal springing settlement has been determined by the iterative scheme. Finally, an experimental test was conducted to validate the results obtained by the analytical method.

Active on Facebook and Failing at School? Meta-Analytic Findings on the Relationship Between Online Social Networking Activities and Academic Achievement

The popularity of social networking sites (SNSs) among adolescents and young adults has raised concerns that the intensity of using these platforms might be associated with lower academic achievement. The empirical findings on this issue, however, are anything but conclusive. Therefore, we present four random-effects meta-analyses including 59 independent samples (total N = 29,337) on the association between patterns of SNS use and grades. The meta-analyses identified small negative effects of $$ \widehat{\rho} $$ = − .07, 95% CI [− .12, − .02] for general SNS use and $$ \widehat{\rho} $$ = − .10, 95% CI [− .16, − .05] for SNS use related to multitasking. General SNS use was unrelated to the time spent studying for school ( $$ \widehat{\rho} $$ = − .03, 95% CI [− 0.11, 0.06]) and no support for the time displacement hypothesis could be found in a meta-analytical mediation analysis. SNS use for academic purposes exhibited a small positive association, $$ \widehat{\rho} $$ = .08, 95% CI [.02, .14]. Hypotheses with regard to cross-cultural differences were not supported.

Bedroom media: One risk factor for development.

Mass media have numerous effects on children, ranging from influencing school performance to increased or reduced aggression. What we do not know, however, is how media availability in the bedroom moderates these effects. Although several researchers have suggested that bedroom media may influence outcomes by displacing other activities (the displacement hypothesis) or by changing the content of media consumed (the content hypothesis), these have rarely been tested directly. This study tested both hypotheses using several outcomes that are associated with bedroom media and some of the underlying mediating mechanisms. The hypotheses were tested using 3 longitudinal samples of varying methods, age, duration, and country. The results indicate that children who have bedroom media are likely to watch larger amounts of screen time which displaced important activities, such as reading and sleeping, which mediated later negative outcomes such as poor school performance. Bedroom media also influence risk for obesity and video game addiction. Children with bedroom media are also likely to be exposed to more media violence. The violent content increased normative beliefs about aggression, which increased physical aggression, providing support for the content hypothesis. This study demonstrates that media can have effects not just from what they show, but also because of what children are not exposed to. Bedroom media are therefore a robust risk factor for several aspects of child development. (PsycINFO Database Record

Better nutritional condition changes the distribution of juvenile dispersal distances: an experiment with Spanish imperial eagles

We investigated the distribution of juvenile dispersal distances of a territorial long‐lived species with deferred maturity, the Spanish imperial eagle Aquila adalberti. Here we used a reintroduction program as an experimental approach to test predictions of different hypotheses about the distribution of juvenile dispersal distances: competition and wandering behavior. We determined maximal juvenile dispersal distances of 59 young eagles; 1) 30 wild non‐manipulated individuals, and 2) 29 tranlocated young under an ad libitum feeding program, released with adults breeding in the area. The competitive displacement hypothesis predicts a leptokurtic distribution of distances in wild non‐manipulated young as well as in released young. Under the ‘wandering’ hypothesis, however, a leptokurtic distribution is expected in wild young but a normal distribution would be expected in young released (with adults in the release area), owing to a general improvement in the nutritional status of released young that have been fed ad libitum, as is usual in reintroduction programs. Additionally, a negative relationship between hatching date and dispersal distances is expected in wild young but no relationship in released young under ad libitum feeding. Mean maximum dispersal distances for all the juvenile eagles was 142.8 km. No differences between sexes were found, nor between populations or between wild and reintroduced young. Wild young distances were not normally distributed, being closer to a Poisson distribution. In contrast, released young with adults (under ad libitum feeding) showed a normal distribution. Wild birds showed a significant negative relationship between dispersal distance and hatching date, with young that hatched late in the season dispersing shorter distances. However, released young under ad libitum feeding showed no significant relationship between hatching date and dispersal distance. These results support the ‘wandering’ hypothesis as the main driver of the distribution of dispersal distances.

Analysis of bi-directional functionally graded plates by FEM and a new third-order shear deformation plate theory

Modern structures and components may require advanced materials whose properties vary continuously not only in one specified direction, but also different other directions. In particular, the bi-directional functionally graded materials (2D-FGMs) introduced are expected to have more effective properties, consequently eliminating commonly awkward problems such as local stress concentrations and delamination. In this paper, buckling and bending behaviors of 2D-FGM plates, which are of great importance in the design and development of engineering applications, are numerically analyzed by a finite element model. The plate kinematics are described using a new third-order shear deformation plate theory (TSDT), without the need for special treatment of shear-locking effect and shear correction factors. The present TSDT theory based on rigorous kinematic of displacements, which is shown to be dominated over other preceding theories, is derived from an elasticity formulation, rather by the hypothesis of displacements. The materials are assumed to be graded in two directions and their effective properties are computed through the rule of mixture. The accuracy of the proposed approach assessed on numerical results is confirmed by comparing the obtained results with respect to reference published solutions. The effects of some numerical aspect ratios such as volume fraction, boundary conditions, thickness to length ratio, etc. on static deflections and critical buckling are numerically studied. The investigation of results confirms that such aforementioned aspect ratios have significant effects on the mechanical behaviors of plates.

Displacement or complementarity? Assessing the relationship between social media and public library usage in the U.S., South Korea, and Singapore

The relevancy of public libraries is often called into question, with some saying that library services have been or will be displaced by, among other things, new media such as social media. This study tested this displacement hypothesis with survey data collected from three nations (the U.S.: N=879; South Korea: N=700; and Singapore: N=987). Ordinal regressions were used to investigate the relationship between the use of social media and nine public library services, taking into account individual demographic differences. The results show that for all three nations, social media use has significant complementary relationships with all nine library services examined. Computer and information literacy training showed the largest effect size. However, signs of displacement effects were observed in the odds ratio statistics, particularly among daily social media users and in reference services, library visits, and time spent in the library, suggesting that where displacement is concerned, these areas warrant extra attention.

Evaluating individual level antecedents and consequences of social media use in Ghana

Social media use has increased tremendously over the last few years, generating immense interest in the phenomenon in both research and practice. Hence, this study takes a quantitative (survey design) approach to empirically examine the user (consumer) level factors that influence social media use, their consequences, and the moderating effects of consumer demographic variables (age and gender). The findings suggest that while external pressure from a consumer's referent group influence their social media use, the consumer's personal values does not. Moreover, social media use generates bridging social capital and subjective wellbeing among consumers. The empirical analysis also shows that consumer demographic variables (age and gender) do not have any significant differences in their use of social media. We shed light on the relative effects of these antecedents on social media use from a holistic perspective employing the social presence theory. This study also contributes to the augmentation and displacement hypotheses of computer-mediated communication and tends to support the augmentation hypothesis. The results will also be useful for firms by employing techniques that would arouse interest and curiosity to attract the attention of social media users.

Disruptive natural selection predicts divergence between the sexes during adaptive radiation.

Evolution of sexual dimorphism in ecologically relevant traits, for example, via resource competition between the sexes, is traditionally envisioned to stall the progress of adaptive radiation. An alternative view is that evolution of ecological sexual dimorphism could in fact play an important positive role by facilitating sex‐specific adaptation. How competition‐driven disruptive selection, ecological sexual dimorphism, and speciation interact during real adaptive radiations is thus a critical and open empirical question. Here, we examine the relationships between these three processes in a clade of salamanders that has recently radiated into divergent niches associated with an aquatic life cycle. We find that morphological divergence between the sexes has occurred in a combination of head shape traits that are under disruptive natural selection within breeding ponds, while divergence among species means has occurred independently of this disruptive selection. Further, we find that adaptation to aquatic life is associated with increased sexual dimorphism across taxa, consistent with the hypothesis of clade‐wide character displacement between the sexes. Our results suggest the evolution of ecological sexual dimorphism may play a key role in niche divergence among nascent species and demonstrate that ecological sexual dimorphism and ecological speciation can and do evolve concurrently in the early stages of adaptive radiation.

Analysis of Asymmetries in the Tax-Spending Nexus in Burundi

Abstract. This study examines the asymmetries in the tax-spending nexus for Burundi using a three-variable model. The study employs a threshold cointegration test with asymmetric adjustment advanced by Enders & Siklos ( 2001 ). The findings indicate that government spending, taxes and grants are cointegrated with asymmetric adjustment. Causality tests from the estimated asymmetric error correction model suggest that in the short run there is an independent relationship between government spending and taxes in Burundi. Pertaining to the impact of grants, the results show that grants encourage the government of Burundi to spend more, but, conversely, they also discourage tax revenue, which is known as the tax displacement hypothesis. The findings further show that only government spending responds to budgetary disequilibrium, and this occurs when the budget situation is worsening. This implies that in Burundi, to restore the equilibrium when the budget situation is worsening, the adjustment is made by reducing spending. A policy intuition arising from this study is that, to reduce budget deficits, Burundi should reduce its grant-dependence and improve its tax collection system as well as cut its spending in sectors where it is not productive and reallocate it to more productive sectors. Keywords. Burundi, Spending, Taxes, Grants, Threshold cointegration, Asymmetric ECM. JEL. C32, E32, H20, H50, H62.

The Indirect Displacement Hypothesis: A Case Study in Washington, D.C.

Stereotypes abound about the clash between newcomers to urban neighborhoods and their longstanding residents. In a case study of Columbia Heights in the District of Columbia, the preferences and attitudes of newcomers and longstanding residents are compared. The comparison will help assess the extent to which indirect displacement pressures in the domain of retail activity might be occurring in Columbia Heights. Data from surveys conducted in 2008 by the Howard University Center for Urban Progress (HUCUP) form the empirical base of this study. A total of 217 completed surveys were received, 116 from an Internet survey and 101 one-on-one street interviews. The sample was split into thirds (according to length of time that the participant lived in the neighborhood) leading to break points at two years and eight years of residency. All respondents who lived in the neighborhood two years or less or eight years or more were kept in the final sample. The former were defined as “newcomers and the latter were defined as “longstanding residents”. There were 77 newcomers and 74 longstanding residents in the final sample. The survey instrument inquired about respondents’ opinions about the availability and quality of stores by type, the variety of stores, and what types of stores they would like to see added to the neighborhood. Respondents were then asked their assessment of the new commercial developments and of the previously existing businesses in the corridor. Chi-square tests were used to test the hypotheses that there were differences between the two populations – newcomers and long-standing residents – in terms of preferences and attitudes. The findings demonstrated significant differences between the two groups in terms of their opinions about the commercial corridor, although both groups were generally pleased with the new retail developments. The analysis of these data weakly supports the hypothesis that indirect factors could heighten pressures for displacement of longstanding residents, but it is argued that the main focus of gentrification studies should continue to be on the direct economic factors affecting longstanding residents during neighborhood revitalization.

A Longitudinal Analysis of Gaming- and Non-Gaming-Related Friendships and Social Support among Social Online Game Players

ABSTRACTResearch examining online games often focuses on their potential to negatively impact players. One of the most common concerns is that playing online with others can displace offline relationships and, consequently, detrimentally affect one’s level of “offline” social support. However, there has been little empirical evidence supporting these causal claims. The current study addresses this by outlining a longitudinal analysis between gaming- and non-gaming-related friendships and social support among a representative sample of social online players (i.e., people who play online video games with others). The results indicate that social online video game play with online or offline friends is not related to perceived social support, positively or negatively, cross-sectionally or longitudinally. Taken together, these results dispute the long-held claims of the social displacement hypothesis and instead suggest that social online video game play does not have negative real-world consequences on players’ offline friendships or levels of offline social support.

Interpreting failure to reject the null hypothesis of displacement from wind turbines in three species of grassland birds: Response to Johnson (2016)

ABSTRACT Johnson (2016) criticized our 3-year study investigating displacement in breeding grassland birds at an operational wind facility in the southern Great Plains. Although Johnson characterized our statistical methods as inappropriate and our study as intentionally misleading, his claims are based on his own view of the appropriate analysis and interpretation. Although we failed to reject the null hypothesis of no displacement in breeding grassland birds at our study site, the main message of our manuscript was a cautionary tale—that is, that at many wind facilities it will be difficult to isolate the effect of distance to turbine from other factors that covary with distance.

Competitive advantage of a dengue 4 virus when co-infecting the mosquito Aedes aegypti with a dengue 1 virus.

BackgroundDengue viruses (DENV) are comprised in four related serotypes (DENV-1 to 4) and are critically important arboviral pathogens affecting human populations in the tropics. South American countries have seen the reemergence of DENV since the 1970’s associated with the progressive re-infestation by the mosquito vector, Aedes aegypti. In French Guiana, DENV is now endemic with the co-circulation of different serotypes resulting in viral epidemics. Between 2009 and 2010, a predominant serotype change occurred from DENV-1 to DENV-4 suggesting a competitive displacement. The aim of the present study was to evaluate the potential role of the mosquito in the selection of the new epidemic serotype.MethodsTo test this hypothesis of competitive displacement of one serotype by another in the mosquito vector, we performed mono- and co-infections of local Ae. aegypti collected during the inter-epidemic period with both viral autochthonous epidemic serotypes and compared infection, dissemination and transmission rates. We performed oral artificial infections of F1 populations in BSL-3 conditions and analyzed infection, dissemination and transmission rates.ResultsWhen two populations of Ae. aegypti from French Guiana were infected with either serotype, no significant differences in dissemination and transmission were observed between DENV-1 and DENV-4. However, in co-infection experiments, a strong competitive advantage for DENV-4 was seen at the midgut level leading to a much higher dissemination of this serotype. Furthermore only DENV-4 was present in Ae. aegypti saliva and therefore able to be transmitted.ConclusionsIn an endemic context, mosquito vectors may be infected by several DENV serotypes. Our results suggest a possible competition between serotypes at the midgut level in co-infected mosquitoes leading to a drastically different transmission potential and, in this case, favoring the competitive displacement of DENV-1 by DENV-4. This phenomenon was observed despite a similar replicative fitness in mono-infections conditions.

The impact of international trade on environmental quality: The case of transition countries

This research presents first empirical time series evidence of the impact of international trade on environmental quality in the case of transition countries. The linkages between international trade and environmental quality are well established both theoretically and empirically in the literature. However, there exists no empirical study concerning environmental quality and international trade. Thus, our research aims at filling this gap. To this extent, fifteen transition countries are selected in order to test the impact of international trade on environmental quality. An econometric model between carbon emissions, energy use, income and trade openness was formed. This model was estimated via ARDL (Autoregressive Distributed Lag) approach to cointegration and GMM (Generalized Method of Moments) procedures. The econometric results from both of these econometric techniques support the existence of the EKC hypothesis only in three transition countries: Estonia, Turkmenistan and Uzbekistan. As for the impact of trade on environmental quality, the econometric results from both techniques vary in different transition countries. To this extent, the displacement hypothesis is validated in the case of Armenia, Estonia, Latvia, Kyrgyzstan and Russia. The paper also discusses policy implications of the empirical results, as well as offering policy recommendations.