Genuine Effect Research Articles

Mediation analysis with structural equation models: Combining theory, design, and statistics

AbstractStatistical tests of indirect effects can hardly distinguish between genuine and spurious mediation effects. The present research demonstrates, however, that mediation analysis can be improved by combining a significance test of the indirect effect with assessing the fit of causal models. Testing only the indirect effect can be misleading, because significant results may also be obtained when the underlying causal model is different from the mediation model. We use simulated data to demonstrate that additionally assessing the fit of causal models with structural equation models can be used to exclude subsets of models that are incompatible with the observed data. The results suggest that combining structural equation modeling with appropriate research design and theoretically stringent mediation analysis can improve scientific insights. Finally, we discuss limitations of the structural equation modeling approach, and we emphasize the importance of non‐statistical methods for scientific discovery.

Consistent analysis of theνμ→νesterile neutrinos searches of ICARUS and OPERA

The two long-baseline experiments ICARUS and OPERA have recently provided bounds on light ($\sim$ eV) sterile neutrinos exploiting the negative results of the $\nu_\mu \to \nu_e$ appearance searches. Both collaborations have performed the data analysis using an effective 2-flavor description. We show that such a simplified treatment neglects sizable genuine 4-flavor effects, which are induced by the interference of the new large squared-mass splitting $\Delta m^2 _{14}$ with the atmospheric one. The inclusion in the data analysis of such effects weakens the upper bounds on the effective appearance amplitude $\sin^2 2\theta_{\mu e}$ approximately by a factor of two. In addition, we evidence that, in a 4-flavor scheme, the flavor oscillations involve also the $\nu_e$ component of the CNGS beam and can suppress the theoretical expectation of the background in a substantial way. The inclusion in the data analysis of the $\nu_e$ disappearance effects leads to a further weakening of the upper bounds on $\sin^2 2\theta_{\mu e}$, which overall are relaxed by a factor of three with respect to those obtained in the effective 2-flavor description.

Overcoming the effects of false positives and threshold bias in graph theoretical analyses of neuroimaging data

Graph theory (GT) is a powerful framework for quantifying topological features of neuroimaging-derived functional and structural networks. However, false positive (FP) connections arise frequently and influence the inferred topology of networks. Thresholding is often used to overcome this problem, but an appropriate threshold often relies on a priori assumptions, which will alter inferred network topologies.Four common network metrics (global efficiency, mean clustering coefficient, mean betweenness and smallworldness) were tested using a model tractography dataset. It was found that all four network metrics were significantly affected even by just one FP. Results also show that thresholding effectively dampens the impact of FPs, but at the expense of adding significant bias to network metrics.In a larger number (n=248) of tractography datasets, statistics were computed across random group permutations for a range of thresholds, revealing that statistics for network metrics varied significantly more than for non-network metrics (i.e., number of streamlines and number of edges). Varying degrees of network atrophy were introduced artificially to half the datasets, to test sensitivity to genuine group differences. For some network metrics, this atrophy was detected as significant (p<0.05, determined using permutation testing) only across a limited range of thresholds.We propose a multi-threshold permutation correction (MTPC) method, based on the cluster-enhanced permutation correction approach, to identify sustained significant effects across clusters of thresholds. This approach minimises requirements to determine a single threshold a priori. We demonstrate improved sensitivity of MTPC-corrected metrics to genuine group effects compared to an existing approach and demonstrate the use of MTPC on a previously published network analysis of tractography data derived from a clinical population.In conclusion, we show that there are large biases and instability induced by thresholding, making statistical comparisons of network metrics difficult. However, by testing for effects across multiple thresholds using MTPC, true group differences can be robustly identified.

Simultaneous suppression of tone burst-evoked otoacoustic emissions: Two and three-tone burst combinations

Previous investigations have shown that components of a tone burst-evoked otoacoustic emission (TBOAE) evoked by a 1 kHz tone burst (TB1) can be suppressed by the simultaneous presence of a 2 kHz tone burst (TB2) or a pair of tone bursts at 2 and 3 kHz (TB2 and TB3 respectively). No previous study has measured this “simultaneous suppression of TBOAEs” for both TB2 alone and TB2 and TB3 from the same ears, so that the effect of the additional presence of TB3 on suppression caused by TB2 is not known. In simple terms, three outcomes are possible; suppression increases, suppression is reduced or suppression is not affected. Comparison of previously reported simultaneous suppression data suggests TB3 causes a reduction in suppression, though it is not clear if this is a genuine effect or simply reflects methodological and ear differences between studies. This issue has implications for previously proposed mechanisms of simultaneous suppression of TBOAEs and the interpretation of clinical data, and is clarified by the present study. Simultaneous suppression of TBOAEs was measured for TB1 and TB2 as well as TB1, TB2 and TB3 at 50, 60 and 70 dB p.e. SPL from nine normal human ears. Results showed no significant difference between mean suppression obtained for the two and three-tone burst combinations, indicating the reduction of suppression inferred from comparison of previous data is likely a result of methodological and ear differences rather than a genuine effect.

Macroscopic bursting in physiological networks: node or network property?

Activity pattern modalities of neuronal ensembles are determined by node properties as well as network structure. For many purposes, it is of interest to be able to relate activity patterns to either node properties or to network properties (or to a combination of both). When in physiological neural networks we observe bursting on a coarse-grained time and space scale, a proper decision on whether bursts are the consequence of individual neurons with an inherent bursting property or whether we are dealing with a genuine network effect has generally not been possible because of the noise in these systems. Here, by linking different orders of time and space scales, we provide a simple coarse-grained criterion for deciding this question.

Behaviourally designed treatments that increase willingness to treatment from families with children suffering from autism spectrum disorder

BackgroundAutism spectrum disorder is a lifelong disability that is not well known by the general population and tends to be associated with social stigma; also, because it involves children, it...

The Impact of a Preoperative Cognitive Behavioural Therapy (CBT) on Dysfunctional Eating Behaviours, Affective Symptoms and Body Weight 1 Year after Bariatric Surgery: A Randomised Controlled Trial.

BackgroundTo examine whether a preoperative cognitive behavioural therapy (CBT) intervention exceeds usual care in the improvements of dysfunctional eating behaviours, mood, affective symptoms and body weight 1 year after bariatric surgery.MethodsThis is a 1-year follow-up of a single centre parallel-group randomised controlled trial (http://clinicaltrials.gov/ct2/show/NCT01403558). A total of 80 (55 females) patients mean (SD) age 44 (10) years were included. The intervention group received 10 weeks of CBT prior to bariatric surgery, and the control group received nutritional support and education. Both groups were assessed at baseline (T0), post CBT intervention/preoperatively (T1), and 1 year postoperatively (T2). Using a mixed modelling statistical approach, we examined if the CBT group improved more across time than the control group.ResultsOur hypothesis was not supported as both groups had comparable improvements in all outcomes except for anxiety symptoms. Body weight declined by 30.2 % (37.3 kg) in the CBT group and by 31.2 % (40.0 kg) in the control group from baseline to follow-up, p = 0.82.There were statistically significant reductions in anxiety and depression symptoms in the CBT group between T0 and T1 and between T1 and T2 for depression only. However, in the control group, the anxiety score did not change significantly. The CBT group showed an earlier onset of improvements in all eating behaviours and affective symptoms than the control group.ConclusionThe 10-week CBT intervention showed beneficial effects preoperatively, but the non-significant group differences postoperatively indicate a genuine effect of surgery.

Introducing a control condition in the classic oddball paradigm: Oddballs are overestimated in duration not only because of their oddness.

Three experiments assessed whether participants perceive infrequent stimuli (oddballs) to last longer than frequent ones (standards). The classical oddball paradigm was modified so that participants judged the duration of a target stimulus which could either be a standard or an oddball. The target was always the fifth stimulus in the stream and all stimuli were presented at predefined spatial positions. These modifications enabled a direct comparison of duration judgments for oddballs and standards. In Experiments 1 and 2 not only the duration of oddballs but also the duration of standards was overestimated by virtually the same amount. In other words, the overestimation of oddballs was not due to their oddness but reflected a different temporal dilation such as the negative time-order error. In Experiment 3, all stimuli were presented at the same spatial position. Again, both oddballs and standards were overestimated, however, oddballs more so. The present results highlight the importance of comparing the judged duration of oddballs and standards when evaluating the size of the genuine oddball effect. Furthermore, the findings suggest that the occurrence of temporal oddball effects can depend on spatial features of stimulus presentation.

The question–behavior effect: Genuine effect or spurious phenomenon? A systematic review of randomized controlled trials with meta-analyses.

Simply answering questions about a specific behavior may change that behavior. This is known as the mere-measurement or question-behavior effect (QBE). Our objective was to synthesize the evidence for the QBE on health-related behaviors. Included studies were randomized controlled trials that tested the effect of questionnaires or interviews about health-related behaviors and/or related cognitions compared with a no-measurement control condition or another form of measurement. Subgroup analyses were conducted to identify potential moderators. 41 studies were included assessing a range of health behaviors. Meta-analyses showed a small overall QBE effect (SMD = 0.09; 95% CI [0.04, 0.13]; k = 33). Studies showed moderate heterogeneity, variable risk of bias, and evidence of publication bias. No dose-response relationships were found from studies comparing more with less intensive measurement conditions. There were no significant differences in QBE by behavior, but QBEs for dental flossing, physical activity, and screening attendance were significantly different from 0. Findings were not altered by whether behavior or cognitions were measured, attitudes were or were not measured, studies used questionnaires or interviews, or outcomes were objective or self-reported. There is some evidence for the QBE on health-related behavior. However, risk of bias within studies and evidence of publication bias indicate that the observed small effect size may be overestimated, especially given that some studies included intervention techniques in addition to providing questionnaires. Preregistered high-quality trials with clear specification of intervention content are needed to confirm if and when measurement leads to behavior change.

Effect of structurally-induced lateral confinement on split Hopkinson pressure bar test specimens of concrete-like materials

In dynamic testing of concrete-like materials, there is a need in distinguishing structural effects from genuine strain-rate effects. In this paper, this generic problem is studied by numerical simulations based on a phenomenological material model available in the commercial finite element (FE) code Abaqus. The numerical results show that the increase of the dynamic increase factor (DIF) with the increase of strain-rate in concrete-like materials in a Split Hopkinson Pressure Bar (SHPB) test is a phenomenon related not only to material strain-rate effects but also to structural effects. It was found that dilation, surface friction and lateral inertia cause lateral confinement, which enhances DIF when the strain-rate is greater than a transition strain-rate in the order of 102 s−1 . Although, genuine strain-rate effect may exist as suggested by meso-scale simulations in previous investigations, the findings in this study show that structural effects have a significant contribution to the increase of DIF, and therefore, it is necessary to correctly calibrate existing phenomenological models and interpret the results obtained from split Hopkinson pressure bar (SHPB) tests.

Is There Really Granger Causality between Energy Use and Output?

We carry out a meta-analysis of the very large literature on testing for Granger causality between energy use and economic output to determine if there is a genuine effect in this literature or whether the large number of apparently significant results is due to publication or misspecification bias. Our model extends the standard meta-regression model for detecting genuine effects in the presence of publication biases using the statistical power trace by controlling for the tendency to over-fit vector autoregression models in small samples. Granger causality tests in these over-fitted models have inflated type I errors. We cannot find a genuine causal effect in the literature as a whole. However, there is a robust genuine effect from output to energy use when energy prices are controlled for.

Electron-spin dynamics induced by photon spins

Strong rotating magnetic fields may cause a precession of the electronʼs spin around the rotation axis of the magnetic field. The superposition of two counterpropagating laser beams with circular polarization and opposite helicity features such a rotating magnetic field component but also carries spin. The laserʼs spin density, which can be expressed in terms of the laserʼs electromagnetic fields and potentials, couples to the electronʼs spin via a relativistic correction to the Pauli equation. We show that the quantum mechanical interaction of the electronʼs spin with the laserʼs rotating magnetic field and with the laserʼs spin density counteract each other in such a way that a net spin rotation remains with a precession frequency that is much smaller than the frequency one would expect from the rotating magnetic field alone. In particular, the frequency scales differently with the laserʼs electric field strength depending on whether relativistic corrections are taken into account or not. Thus, the relativistic coupling of the electronʼs spin to the laserʼs spin density changes the dynamics not only quantitatively but also qualitatively as compared to the nonrelativistic theory. The electronʼs spin dynamics are a genuine quantum mechanical relativistic effect.

Finance and growth: new evidence from meta-analysis

Purpose– The purpose of this paper is to bridge the gap between the pros and cons of a questionable finance-growth nexus.Design/methodology/approach– Over 20 fundamental characteristics that have influenced the debate over the last decades have been examined. The empirical evidence is based on 196 outcomes from 20 studies. The author assesses the degree of heterogeneity and identify causes of the observed differentiation.Findings– The findings also show evidence of publication bias. Overall, a genuine effect exists between financial development and economic growth. A finance-growth nexus might not be appealing in our era because of: endogeneity-based estimations, publication bias, and effects of financial activity. A historical justification has also been discussed.Practical implications– Encouraging the publication of results with findings that are not consistent with the mainstream positive finance-growth nexus should provide new scholarly insights into the relationship. Depending on the specific context of sampled countries, the role of policy has also been to encourage financial development through measures that may expose countries to negative external shocks like financial crises. Policy makers that have been viewing the challenges of development exclusively from this point of view for the rewards of growth may not be getting the financial dynamics correctly.Originality/value– Very few meta-analysis studies have focused on the finance-growth nexus.

The Masculine Urge of Jack Kerouac's Haiku

During 1950s, dissatisfied with state of both American culture literature, Beat writers sought cure for Western ills Japanese philosophy (Zen Buddhism particular) poetry (haiku particular). Among prominent Beats to produce haiku are Gary Snyder, Allen Ginsberg, Philip Whalen, Cid Corman. However, perhaps most interesting Beat haikuist is Jack Kerouac, far better known for his sprawling, often manic novels. While 2003 publication of Book of Haikus sparked renewed interest fivehundred-plus haiku Kerouac wrote, critics initially dismissed these three-line poems. Ann Charters Gerald Nicosia, major biographers, generally mention haiku passing, as something Kerouac did between his more important works. James T. Jones observes that, after 1955 publication of Mexico City Blues, Kerouac's verse lost intensity effectiveness, and he concentrated more on haiku his declining years (12). Alison Kirby Record argues that Kerouac occasionally achieved genuine haiku effects his early experiments form, but the majority of these efforts ... are flawed because they rely too heavily on too-thin understanding of Zen Buddhism and, consequently, fail to replicate Japanese models (87). The aesthetic merits of these poems are, of course, debatable. What is more certain is that they function effectively as expressions of Kerouac's dissatisfaction: with consumerism, prevailing literary practices, his own masculinity.Understandably, critics have focused on relationship between Kerouac's much-discussed discovery of Zen early 1954 his haiku, which he probably began writing at about this time continued writing up to his death. Charters, foremost Kerouac scholar, notes that writer composed haiku on typescript of Some of Dharma, an unpublished treatise on Buddhism written between March 1954 late Spring/early Summer 1955 (204; 210-11; 214). In various letters written 1956, Kerouac either mentioned or included haiku. He also wrote number of haiku while serving as fire-lookout on Desolation Peak summer of 1956 (Charters 262), he published three Berkeley Bussei that same year. We know that he retained his interest form 1959, as he wrote some haiku for Frank O'Hara (Charters 306-07) collaborated with Albert Saijo Lew Welch on haiku sequence Trip Trap (Nicosia 606). As late as 1962, Kerouac planned to collaborate with his friend Matsumi Kanemitsu on book about cats; Kerouac was to write haiku Kanemitsu was to illustrate (Nicosia 643).Those critics who examine Zen elements of Kerouac's haiku-specifically Sarah Haynes Yoshinobu Hakutani-tend to draw on poet's familiarity with Reginald H. Blyth's four-volume Haiku. From Blyth, Kerouac would have learned that haiku had evolved over time to its current form as three-line, seventeen-syllable poem arranged five, seven, five ji-on (syllable sounds). Blyth also emphasizes (or overemphasizes, according to some scholars) Zen underpinnings of haiku, including need for haiku poet to attain state of mind in which we are not separated from other things, are indeed identical with them, yet retain our own individuality (I, iii). Other Zen concepts manifested haiku include mu, a state of nothingness that is absolutely free of any human-centered thought or emotion; sahi, quiet beauty or lonely grace; wahi, an aesthetic appreciation of beauty stemming from poverty; yugen, mystery inexplicability, which surround order of universe (Hakutani, Richard Wright 276-77; 280; 290), satori, moment of enlightenment. Yet another important element of haiku is mention of specific season, often implied through employment of kigo, so-called season word.The problem with positing Kerouac's haiku within Zen framework is tendency to read them for what is not there. …

Quantum-Memory Effects in the Emission of Quantum-Dot Microcavities

The experimentally measured input-output characteristics of optically pumped semiconductor microcavities exhibits unexpected oscillations modifying the fundamentally linear slope in the excitation power regime below lasing. A systematic microscopic analysis reproduces these oscillations, identifying them as a genuine quantum-memory effect, i.e., a photon-density correlation accumulated during the excitation. With the use of projected quantum measurements, it is shown that the input-output oscillations can be controlled and enhanced by an order of magnitude when the quantum fluctuations of the pump are adjusted.

THE FINANCIAL DEVELOPMENT AND GROWTH NEXUS: A META‐ANALYSIS

AbstractWe conduct a meta‐analysis of the literature of financial development and economic growth. We cover a large number of empirical studies and estimations that have been published in journal articles. We measure the degree of heterogeneity and identify the causes of the observed differentiation. Among the most significant factors behind this heterogeneity is the choice of financial‐variable proxies, the kind of data used as well as whether a study takes into account the issue of endogeneity. Our results suggest that the empirical literature on the finance–growth nexus is not free from publication bias. Also, a genuine positive effect exists between financial development and economic growth.

Microsaccades and drift are similarly modulated by stimulus contrast and anticipation

Microsaccades are considered to be involuntary fixational eye movements in addition to a slower random-walk like movement called drift. Following a perceptual event, as well as prior to anticipated events, the microsaccades are typically inhibited and later released in a time course that depends on stimulus properties and cognitive factors. We examined whether the drift also follows the same inhibitory pattern. Method: During fixation observers (n=16) viewed passively a sequence of randomly ordered Gabor patches with varied contrast flashed every 1 second. In a second experiment, observers (n=22) performed a continuous performance task (CPT) with stimuli presented every 2 seconds. The time courses of microsaccade rate, pupil size and drift amplitude were computed relative to stimulus onset based on high speed eye tracking data. Drift was computed after filtering out all traces of saccades, using "box-counting" and the position range within a sliding window. Overall, ~20,000 trials were examined. Results: The drift time course was similar to that of microsaccade rate, though with larger variability. It showed a similar dependence on contrast, and on the history of preceding events. Drift inhibition was correlated with microsaccade inhibition across individuals in the pre-stimulus period of the CPT. Moreover, it persisted in trials with no microsaccades, ruling out an indirect effect of microsaccades on drift. To minimize the possible crosstalk artifact of large pupil size changes on position, we analyzed iso-luminance stimuli as well as pre-stimulus periods. In these conditions, we found no correlation between the pupil derivative and drift, suggesting a genuine drift effect. Conclusion: The drift, like microsaccades and perhaps other types of body movement, appears to show a "freeze effect" in response to perceptual events as well as prior to anticipated events. The pattern of this effect conveys information on the time course of the cognitive processes involved. Meeting abstract presented at VSS 2014

Hadronic resonance production measured by ALICE at the LHC

Hadronic resonances constitute a valuable probe for the properties of the medium formed in heavy-ion collisions. In particular, they provide information on particle-formation mechanisms, the properties of the hadronic medium at freeze-out, and they contribute to the systematic study of energy loss and recombination. The study of resonance production in other collision systems such as pp and p–Pb forms a necessary baseline to disentangle initial-state effects from genuine medium-induced effects. The production of the K ⁎ ( 892 ) 0 and ϕ ( 1020 ) resonances has been measured at mid-rapidity in different collision systems at LHC energies using the ALICE detector. Resonances are reconstructed via their hadronic decay in a wide momentum range, by exploiting the excellent particle-identification capabilities of the Time-Projection Chamber and the Time-Of-Flight system. First results on K ⁎ ( 892 ) 0 and ϕ ( 1020 ) production in p–Pb collisions at s NN = 5.02 TeV at the LHC are presented. The resonance transverse momentum spectra and yields are measured as a function of the multiplicity of p–Pb collision. Ratios of resonance to long lived hadron production in Pb–Pb are compared with the same quantities measured in pp and p–Pb, in order to investigate rescattering effects. The ratio of ϕ to protons and pions as a function of p T suggests that in central Pb–Pb collisions it is the mass which drives the spectra shapes at low and intermediate p T , as in a hydrodynamically-evolving system. The nuclear modification factors ( R AA , R pPb ), recently measured up to high p T for resonances, are consistent with those of the stable hadrons.

Cosmological perturbations inQCD¯-inflation: Estimates confronting the observations, including BICEP2

We discuss a new scenario for early cosmology, when inflationary de Sitter phase dynamically emergent. This genuine quantum effect occurs as a result of dynamics of the topologically nontrivial sectors in a (conjectured) strongly coupled QCD- like gauge theory with scale ${\Lambda_{\overline{\mathrm{QCD}}}} \sim 10^{17} $ GeV in expanding universe. Inflaton in this ${\overline{\mathrm{QCD}}}$- inflation framework is an auxiliary non-propagating field, similar to an effective field known to emerge in topologically ordered condensed matter systems. Number of e-folds in the ${\overline{\mathrm{QCD}}}$-inflation framework is determined by the gauge coupling constant at the moment of inflation, and estimated as $N_{\rm inf}\sim \alpha^{-2}(H_0)\sim 10^2$. We analyze the equation of state in this framework at the end of inflation in terms of the gauge dynamics and confront our estimates with observations. We make predictions for the tensor tilt, $n_t \simeq -0.02$, the running of the tensor tilt $\alpha_t= {\partial n_t}/{\partial \ln k}\sim \alpha^4(H_0)\sim 10^{-4}$ and the running for the spectral index $\alpha_s= {\partial n_s}/{\partial \ln k}\sim \alpha^4(H_0)\sim 10^{-4}$ in terms of the same gauge coupling constant $\alpha(H_0)$, which is fixed in our framework by recent BICEP2 measurements of the tensor fraction $r\simeq 0.2$.

Education and Economic Growth: A Meta-Regression Analysis

Summary This paper surveys the literature which examines the effect of education on economic growth. Specifically, we apply meta-regression analysis to 57 studies with 989 estimates and show that there is substantial publication selection bias toward a positive impact of education on growth. Once we account for this, the genuine growth effect of education is not homogeneous across studies, but varies according to several factors. Specifically, it is attributed to differences in education measurement and study characteristics, mainly model specification as well as type of data used, and the quality of research outlets where studies are published, e.g., academic journals vs. working papers.