Positive Feedback Effect Research Articles

Plant-microbial feedback in secondary succession of semiarid grasslands

Plant–soil feedback (PSF) is an important driver of plant community dynamics. The role of plant species in PSF has been emphasized for secondary succession processes; however, microbial responses to PSF and the underlying mechanisms responsible for their effects on plant succession remain poorly understood, particularly in semiarid grassland ecosystems. Here, we conducted a greenhouse experiment using soil collected from early-, mid-, and late-successional plant communities to measure net pairwise PSF for species grown under monoculture. Soils conditioned by pre-successional species had a positive feedback effect on subsequent plant species, whereas soil conditioned by subsequent plant species had a negative feedback effect on pre-successional species. The feedback effect of plants from different successional stages on soil bacterial and fungal communities was mainly positive. However, the bacterial genera in the soil conditioned by early- and mid-successional species and fungal classes in the soil conditioned by early- successional species had a negative feedback effect on late-successional species. Thus, the effects of soil fungal and bacterial communities on species in other successional stages varied with taxonomic level. Our results provide insight into the manner in which soil microbial communities influence PSF responses during secondary succession processes.

Economic development and climate change. Which is the cause and which the effect?

Energy efficiency has established as a trending topic in scholarly research in the last four decades. Lately, the purpose of that research strand has broadened so to tackle the increase of greenhouse gas emissions and the issues related to climate change. Human beings and their mass production and consumption activities are thought to be a primary source of climate-altering emissions. However, that assumption has been seldom tested. Here we aim to provide a methodological and empirical framework to check for the causal nexus that allegedly ties together demographic growth, economic development, and climate change. The analysis is based on the historically reconstructed series of several variables that span over the last centuries. Besides, it is based on the class of ARIMAX-ARCH models. The results show evidence for bidirectional causation between human growth and climate change. In particular, we find that solar irradiance and gross domestic product are significant predictors of temperature anomalies. Furthermore, temperature anomalies and solar irradiance are found to exert a positive feedback effect on the growth rate of gross domestic product. As regards the causality measures, despite the strength of the univariate component, the contribution of the exogenous factors is strongly significant in all the estimated models. The analysis we carry out suggests framing climate change within a set of long-run trends.

Impact of Total Asset Turnover Ratios on Equity Returns: Dynamic Panel Data Analyses

This paper is an empirical exploration of the impact of total asset turnover ratios on stock returns of 1961 US public firms in different types of industries from 2001 to 2015. Stock prices are significantly influenced by operating performance of a company in efficiently utilizing its assets. For that matter, operating efficiency (as measured by total asset turnover ratio) plays a role in portfolio investment decisions. Pedroni’s heterogeneous panel co-integration procedures, associated bivariate error-correction model (ECM), dynamic ordinary least squares (DOLS) and generalized method of moments (GMM) are applied. Both stock returns and total asset turnover ratios in levels are nonstationary with I (1) behavior. Subsequently, both variables are found cointegrated. The panel ECM estimates suggest convergence of variables toward long-run equilibrium at moderate pace with short-run interactive positive feedback effects. Again, both DOLS and GMM estimates reveal short-run contemporaneous positive effects of total asset turnover ratios on stock returns in levels. In view of the findings of this study, firms should strive to improve operating efficiency, among others, to enhance competitiveness and thereby to boost their stock prices for rewarding shareholders.

Novel Method to Evaluate Diagnostic Shifting After a Pediatric Antibiotic Stewardship Intervention

Background: Audit-and-feedback interventions track clinician practice patterns for a targeted practice behavior. Audit and feedback of antibiotic prescribing data for acute respiratory infections (ARI) is an effective stewardship strategy that relies on administrative coding to identify eligible visits for audit. Diagnostic shifting is the misclassification of a patient’s diagnosis in response to audit and feedback and is a potential unintended consequence of audit and feedback. Objective: To develop a method to identify patterns consistent with diagnostic shifting including both positive shifting (improved diagnosis and documentation) and negative shifting (intentionally altering documentation of diagnosis to justify antibiotic prescribing), after implementation of an audit-and-feedback intervention to improve ARI management. Methods: We evaluated the intervention effect on diagnostic shifting within 12 University of Utah pediatric clinics (293 providers). Data included 66,827 ARI diagnoses: pneumonia, sinusitis, bronchitis, pharyngitis, upper respiratory infection (URI), acute otitis media (AOM), or serous otitis with effusion (OME). To determine whether rates of ARI diagnoses changed after the intervention, we developed logistic generalized estimating equation (GEE) models with robust sandwich standard error estimates to account for clinic-wise clustering. Outcomes included the change in each ARI diagnosis relative to the competing 6 diagnoses included in audit-and-feedback reports before and after intervention implementation. Models tested for a change in outcomes after the intervention (ie, diagnostic shift) after adjustment for month of diagnosis. For each diagnosis, we estimated the population attributable fraction (PAF) for antibiotic prescriptions due to combined shifts in diagnostic frequencies and prescription rates for each diagnosis. The PAF is the estimated fraction of antibiotic prescriptions that would have changed under a population-level intervention. Results: In month-adjusted analyses, diagnoses of pneumonia and OME decreased after the intervention: odds ratio (OR), 0.46 (95% CI, 0.31–0.68) and OR, 0.81 (95% CI, 0.67–0.99), respectively. In addition, URI diagnoses increased: OR, 1.05 (95% CI 1.00, 1.11). We did not detect changes in the diagnosis rates of sinusitis, AOM, bronchitis, and pharyngitis post intervention. The intervention effect on the PAF for antibiotics prescriptions was consistently positive but relatively small in magnitude. PAF was highest for URIs (PAF, 8.87%), followed by AOM (PAF, 3.56%) and sinusitis (PAF, 2.76%), and was lowest for pneumonia and bronchitis (PAF, 0.41% for both). Conclusions: Our analysis found minimal evidence overall of diagnostic shifting after a stewardship intervention using audit and feedback in these pediatric clinics. Small changes in diagnostic coding may reflect more appropriate diagnosis and coding, a positive effect of audit and feedback, rather than intentional negative diagnostic shift.Funding: NoneDisclosures: None

Controls on eruption style at Rabaul, Papua New Guinea – Insights from microlites, porosity and permeability measurements

Rabaul in Papua-New-Guinea is an extremely active andesitic caldera complex that displays a large spectrum of eruption styles. Since 1878, four sub-plinian (VEI-4) and ten VEI 1–3 (effusive, strombolian, vulcanian) eruptions occurred from Tavurvur and Vulcan, the two main active vents. We study pumiceous tephra, ballistic bombs and a lava flow from five of these eruptions to investigate (1) magma ascent rates and (2) volatile escapement processes during the ascent.We measured total and connected porosities, permeability, and connectivity and related these results with measurements of crystallinity, Microlite Number Density (MND) and Microlite Size Distribution (MSD) of plagioclases and pyroxenes. From the application of existing percolation models, we find that explosive products yield a percolation threshold comprised between 50 and 60 vol% total porosity, while petrophysical parameters of the lava flow and some of the ballistic bombs are explained by bubble collapse driven by surface tension. Sub-plinian products show low phenocryst contents (5–15 vol%), microlites generated by nucleation-driven crystallization or glassy textures due to kinetic crystallization lags. Vulcanian, strombolian and effusive products on the other hand, show medium to high phenocryst contents (15–40 vol%) and microlites that crystallised by growth-dominated processes. MSDs in sub-plinian pumiceous tephra constitute a partial record of drastic magma acceleration. In comparison, MSDs in vulcanian and strombolian ballistic bombs and lava flow show a classic pattern of crystallization at a steady-state due to gradual magma ascent.We find that magma feeding sub-plinian eruptions ascends 2–3 orders of magnitude faster than magma feeding vulcanian/effusive eruptions (≥ 1–100 m/s vs 0.1 m/s). In the case of sub-plinian products, due to the important kinetic crystallization lag, these speeds cannot be estimated using microlite crystallization triggered by decompression as a proxy. Combining petrophysical and textural measurements we suggest that slight changes in initial conditions in the reservoir such as crystallinity or the presence of exsolved volatiles, can have a profound impact on the ascent rate and generate positive or negative feedback effects leading to powerful sub-plinian activity or intermittent vulcanian/ passive effusive activity respectively.

Assessing the responses of Sphagnum micro-eukaryotes to climate changes using high throughput sequencing.

Current projections suggest that climate warming will be accompanied by more frequent and severe drought events. Peatlands store ca. one third of the world’s soil organic carbon. Warming and drought may cause peatlands to become carbon sources through stimulation of microbial activity increasing ecosystem respiration, with positive feedback effect on global warming. Micro-eukaryotes play a key role in the carbon cycle through food web interactions and therefore, alterations in their community structure and diversity may affect ecosystem functioning and could reflect these changes. We assessed the diversity and community composition of Sphagnum-associated eukaryotic microorganisms inhabiting peatlands and their response to experimental drought and warming using high throughput sequencing of environmental DNA. Under drier conditions, micro-eukaryotic diversity decreased, the relative abundance of autotrophs increased and that of osmotrophs (including Fungi and Peronosporomycetes) decreased. Furthermore, we identified climate change indicators that could be used as early indicators of change in peatland microbial communities and ecosystem functioning. The changes we observed indicate a shift towards a more “terrestrial” community in response to drought, in line with observed changes in the functioning of the ecosystem.

How the process of transitions shapes the politics of decarbonization: Tracing policy feedback effects across phases of the energy transition

Policy feedback has been applied as a theoretical concept in exploring the political dynamics of domestic energy transitions. However, theory-oriented work is needed to apply the concept to studies of technological change processes. This article explores two technology feedback effects – technology maturity and socio-technical fit – that add external pressure for policy adaption. These are theorized as enabling a correction mechanism through learning that can partly counter positive policy feedback effects. Thus, the co-evolution process between renewable energy policy instruments and technologies is conceptualized as involving increasing return processes leading to sticky policies, balanced by correction mechanisms that support a more plastic view on policies. This argument is explored through a longitudinal case study of the co-evolution of policy instruments and solar photovoltaics in California.

Arbuscular mycorrhizal fungi help explain invasion success of Solidago canadensis

The importance of soil microbes as a whole has long been recognized in plant invasions, yet relatively few studies address the relative importance of different soil microbial guilds. To this end, we collected soils that were conditioned by plants in 18 pairs of invaded and uninvaded communities and conducted an assemblage experiment (invasive Solidago canadensis and five native plants) via four inoculations. Arbuscular mycorrhizal fungi (AMF) increased the growth of S. canadensis and its competitive suppression (the potential of S. canadensis to suppress its neighboring native plants). The positive feedback effect of AMF on S. canadensis was stronger than their negative feedback effect on five native plants. Solidago canadensis grew larger and had lower competitive suppression in conspecific soils than heterospecific soils. These findings suggest that AMF play a crucial role in driving S. canadensis invasions and also highlight that conspecific and heterospecific soils contribute to the success of S. canadensis through different pathways.

The effects of performance feedback on organizational citizenship behaviour: a systematic review and meta-analysis

ABSTRACT Performance feedback is a managerial practice whose effects widely impact job satisfaction and commitment. Job satisfaction and commitment represent antecedents of organizational citizenship behaviour (OCB), denoting a willingness to cooperate. However, there has been little research on the direct relationship between performance feedback and OCB. Previous works addressed their mediating role, such as organization-based self-esteem, job satisfaction or other measures of discretionary effort. Our search of peer-reviewed studies containing measures of feedback and OCB found 15 studies, containing 21 critically appraised correlation measures. While descriptive findings of the systematic review showed a small correlation, studies that contained measures of feedback frequency were more likely to include higher reports of OCB than studies containing measures of feedback properties. After computing correlation scores to effect sizes, findings from the meta-analysis indicated a small average effect size of performance feedback on OCB (radj =.27, 95% CI =.21 –.33). The discussion addresses the differential effects of positive and negative feedback, frequency, and properties of feedback on reports of OCB levels (by employees and supervisors), as well as further applications for line management.

Robust turbulence simulation for particle-based fluids using the Rankine vortex model

We propose a novel turbulence refinement method based on the Rankine vortex model for smoothed particle hydrodynamics (SPH) simulations. Surface details are enhanced by recovering the energy lost due to the lack of the rotation of SPH particles. The Rankine vortex model is used to convert the diffused and stretched angular kinetic energy of particles to the linear kinetic energy of their neighbors. In previous vorticity-based refinement methods, adding more energy than required by the viscous damping effect leads to instability. In contrast, our model naturally prevents the positive feedback effect between the velocity and vorticity fields since the vortex model is designed to alter the velocity without introducing external sources. Experimental results show that our method can recover missing high-frequency details realistically and maintain convergence in both static and highly dynamic scenarios.

Supervisor Feedback and Employee Feedback Seeking Behaviors: Testing a Mediated Moderation Model

In this three-wave field study, we investigate how supervisor feedback affects employees’ subsequent feedback inquiry and monitoring behaviors. Drawing from Feedback Intervention Theory, we identify positive and negative feedback and perceived feedback quality as critical cues of supervisor feedback. Further, we propose that these feedback cues interact in shaping employee psychological empowerment and perceptions of supervisor abusiveness, which in turn affect employee future feedback inquiry and monitoring behaviors differently. Consistent with our expectations, perceived feedback quality moderates the relationship between positive supervisor feedback and employee psychological empowerment, which in turn relates to feedback inquiry but not monitoring. Specifically, only when perceived feedback quality is high, there is positive effect of positive supervisor feedback on subsequent feedback inquiry via psychological empowerment. Further, as expected, perceived feedback quality moderates the relationship between negative supervisor feedback and employees’ perceptions of supervisor abusiveness, which in turn relates to feedback monitoring but not inquiry. Specifically, only when perceived feedback quality is high, negative supervisor feedback has an indirect effect on feedback monitoring via perceptions of supervisor abusiveness. We discuss the theoretical and practical implications of the findings.

Psychological Capital and Performance: Roles of Thought Self- Leadership, Engagement, and Feedback

The purpose of this study is to examine the effect of sales employee’s psychological capital (PsyCap) on performance through the interplay of work engagement and performance feedback. It also advances the agenda of examining thought self-leadership (TSL) as an antecedent of PsyCap. A hypothesized model was tested using survey data collected from salespeople from different industries in India. A structural equation model was used to test the hypotheses. The results demonstrate that TSL drives PsyCap in salespeople. The results also suggest an interesting interplay between a salesperson’s PsyCap and his/her sales performance through work engagement as a mediator for PsyCap and sales performance. The results for the moderating effect of positive and negative feedback on the effect of PsyCap on work engagement were not significant. The research suggests that a salesperson’s PsyCap relates positively to sales performance through work engagement. It also suggests that TSL strategies strengthen the salesperson’s PsyCap. The results suggest that organizations should invest in training to enhance TSL which will lead to enhanced performance through effective personal resources such as PsyCap. The results of the study enrich the extant information on PsyCap and sales performance linkages by suggesting mediation mechanisms and proposing an integrated framework with work engagement

Meaning of work in a group of school principals: the role of organizational variables

PurposePrincipals’ beliefs about their profession are of great interest for schools in terms of organizational development and success. Furthermore, as meaning is a dimension of eudaimonic well-being, studying the principal meaning of work allows us to deepen the knowledge about their professional well-being, too. According to studies on non-educational contexts, the meaning of work is influenced by several organizational variables (such as possibilities for professional development and organizational commitment). Despite this, several school workers still lack to recognize the role played in this regard. Trying to fulfill these gaps partially, the purpose of this study is to verify the incremental effect of organizational dimensions and positive feedback from colleagues above and beyond positive beliefs about work.Design/methodology/approachAn Italian version of the COPSOQ II adapted to school principals was administered to 1,616 school principals. Hierarchical multiple regression was conducted, considering three blocks of variables, namely, positive personal beliefs about work (job satisfaction and self-efficacy); organizational dimensions (role clarity, possibilities for development and sense of belonging to the workplace); positive feedback from colleagues.FindingsOverall, the variables explained 45% of the variance of the meaning of work. While organizational variables accounted for an incremental 24% of the variance, above and beyond the personal experience of work (F (5, 1,610) = 267.378, p = 0.000), positive feedback from colleagues did not show a significant effect originality. To the best of the authors’ knowledge, this is the first study regarding the meaning of work at school with specific reference to school principals.Originality/valueTo the best of the authors’ knowledge, this is the first study regarding the meaning of work at school and with specific reference to school principals.

The effects of positive and negative verbal feedback on repeated force production

Studies indicate that providing subjects with positiveaugmented feedback (PAF) enhances motor learning and performance compared to negative- (NAF), or no-feedback. However, in the majority of these studies, the performance feedback was provided relative to a peer-group (e.g., “your performance is higher/lower than the norm”). Here we examined how different, and less explored types of PF and NF, influenced repeated force production of 22 resistance-trained subjects (50%-males). On three occasions, subjects completed 12 isometric maximal voluntary contractions (MVC) with their elbow flexors, while electromyography (EMG) was collected from their biceps and triceps brachii muscles. After every second repetition, subjects received either PF (e.g., “You are looking great.”), NF (e.g., “You are not trying.”), or no-feedback. All measurements were normalized to pre-test MVCs and reported aspercentages. Subjects applied greater forces in the NF condition compared to the PF (4.3%, 95%CI: 2.8, 5.8) and no-feedback (7.9%, 95%CI: 6.4, 9.4) conditions. Similarly, subjects demonstrated greater biceps EMG activity in the NF compared to the PF (6.6%, 95%CI: 3.7, 9.4) and no-feedback (2.8%, 95%CI: 9.9, 15.6) conditions. We speculate that NF can lead subjects to exert greater forces bysignaling that their efforts are lacking. These results indicate that under some circumstances, NF can have practical benefits over no-feedback and even PF; however, we note that NF should be delivered with caution since it may also hinder motivation and self-efficacy over time.

Warming Increases Nitrous Oxide Emission from the Littoral Zone of Lake Poyang, China

Littoral wetlands are globally important for sustainable development; however, they have recently been identified as critical hotspots of nitrous oxide (N2O) emissions. N2O flux from subtropical littoral wetlands remains unclear, especially under the current global warming environment. In the littoral zone of Lake Poyang, a simulated warming experiment was conducted to investigate N2O flux. Open-top chambers were used to raise temperature, and the static chamber-gas chromatograph method was used to measure N2O flux. Results showed that the littoral zone of Lake Poyang was an N2O source, with an average flux rate of 8.9 μg N2O m−2 h−1. Warming significantly increased N2O emission (13.8 μg N2O m−2 h−1 under warming treatment) by 54% compared to the control treatment. N2O flux in the spring growing season was also significantly higher than that of the autumn growing season. In addition, temperature was not significantly related to N2O flux, while soil moisture only explained about 7% of N2O variation. These results imply that N2O emission experiences positive feedback effect on the ongoing warming of the climate, and abiotic factors (e.g., soil temperature and soil moisture) were not main controls on N2O variation in this littoral wetland.

Modeling Temperature-Dependent Sex Determination in Oviparous Species Using a Dynamical Systems Approach.

In many oviparous species, the incubation temperature of the egg determines the sex of the offspring. This is known as temperature-dependent sex determination (TSD). The probability of the hatched offspring being male or female varies across the incubation temperature range. This leads to the appearance of different TSD patterns in species such as FM pattern where females are predominately born at lower temperature and males at higher temperature, FMF pattern where the probability of female being born is higher at extreme temperatures and of the male being born is high at intermediate temperatures. We analyze an enzymatic reaction system proposed in the literature involving sex hormones with positive feedback effect to understand the emergence of different TSD patterns. The nonlinearity in the model is accounted through temperature sensitivity of the reaction rates affecting the catalytic mechanism in the reaction system. We employ a dynamical systems approach of singularity theory and bifurcation analysis to divide the parameter plane of temperature sensitivities into different regions where different TSD patterns are observed. Bifurcation analysis in association with the delineation of the parameter space for different TSD pattern has led to the identification of a subspace where all the TSD patterns observed in nature can be realized. We also show how modulation of the sex hormone in the species can be used to change the probability of occurrence of a specific sex, thereby preventing the extinction of endangered species.

A field study on the effects of combined biomanipulation on the water quality of a eutrophic lake

Lake eutrophication has become a serious environmental problem in China. Manipulations covering more elements of trophic pyramid are methods for lakes to obtain clear water state and should be studied in detail. In the present study, Meishan Dongpo Lake was divided into two parts, and a combined biomanipulation project was conducted in one part (RLake), and the other part was used as a control (CLake). Species of submerged-plant, fish, macrobenthos, and zooplankton were screened and a certain number of them were added to adjust the eco-chain in RLake. After restoration, the coverage of submerged macrophytes reached >85%; zooplankton greater than 0.6 mm in size increased in number, and the ratio of zooplankton biomass to chlorophyll-a (Chl-a) concentration increased. The dominant fish species changed, and disturbance of the sediment was reduced. The average density of mollusks in RLake was 111.5 ± 19.8 ind m−2, which was much higher than that in CLake (36.7 ± 2.1 ind m−2). Water quality and clarity were substantially improved, and nutrient concentrations, particularly total phosphorus, total nitrogen, and Chl-a were significantly reduced. The aquatic community parameters were negatively correlated with the nutrient parameters and Chl-a. The ecological restoration have adjusted the aquatic ecosystem in RLake, and many positive feedback effects among the aquatic communities made them remove internal nutrients and Chl-a more efficiently.

THE STUDY OF RELATIONSHIP BETWEEN TOBIN’S Q AND US STOCK PERFORMANCE OF SELECTED FIRMS

The objective of study was to test the dynamic effects of changes in Tobin’Q on stock prices of selected 249 US public companies of different industry categories. Panel unit roots tests and cointegration tests are implemented. Next, DOLS and GMM models are estimated. Annual data for the 2004-2012 period are used for the above selected US companies. Panel unit root tests provide somewhat mixed evidence of non-stationarity of both variables. There is clear evidence of cointegration between the above variables. The negative coefficient of the error-correction term shows convergence toward long-run equilibrium, though at slow pace. The estimates also reveal shortrun net positive interactive feedback effects between the variables. Both DOLS and GMM estimates display similar picture of overvaluation of stocks in terms of upward movement in Tobin’s Q beyond 0-to-1 range. For most parts of the sample period, the US stock market was in declining mode due to heightening of economic uncertainties during the Great Recession and several years beyond. Tobin’s Q should be improved to boost stock prices. This is more of a long-run phenomenon. In the short run, both reinforce each other. The topic is unique and the existing literature on this topic is scant. Relatively new econometric techniques have been applied for estimation using panel data. The results are quite insightful, in our view.

Why are highway speed limits really justified? An equilibrium speed choice analysis

Speed externalities – the impacts that a driver’s speed choice imposes on others – are usually quoted to justify highway speed regulation in the form of maximum speed limits. However, speed externalities could already be internalized if a pre-existing policy were in place that is related to speed, questioning the traditional rationale supporting speed limits. Given the relationship between speed and fuel consumption and the omnipresence of fuel taxes around the world, it comes as a surprise that pre-existing taxes on motor fuel are completely missing in the debate on the general appropriateness of speed regulation. In this paper we develop an economic equilibrium model of highway speed choice accounting for (i) a market failure – speeding externalities capturing the fact that drivers do not internalize the adverse consequences of speeding on other highway users and the society as a whole; (ii) a famous speed related behavioral anomaly – causing adverse effects drivers impose on themselves by falsely predicting the time saving potential of speed; (iii) a pre-existing fuel tax – closing the wedge between the privately and socially optimal speed. The latter creates a ‘government feedback effect’ reflecting the positive feedback effect of speed on fuel tax revenue and so the broader beneficial fiscal impacts of speed choice ignored by drivers. Numerical computations for Germany indicate a dominant ‘government feedback effect’ ((iii) outweighs (i)) for mean speeds up to around 120 km/h presuming fully variable travel time budgets and beyond that speed level when drivers put (some of the) travel time savings from speeding into more highway traveling. This implies that speed externalities are largely internalized and that the externality rationale in favor of speed regulation does not apply to the majority of drivers. Nevertheless, a moderate speed limit on German highways of 130 km/h would probably not compromise economic efficiency, at least as long as the share of diesel cars is significant. Generally, when drivers are subject to lack of rationality leading to excess speeding, (iii) is not able to outweigh (i). Then, speed limits remain highly warranted provided that appropriate “nudging” is not available. The numerical finding is likely to hold for a large number of European countries too but probably not for North American countries where fuel taxes are considerably lower.

Well Done! Effects of Positive Feedback on Perceived Self-Efficacy, Flow and Performance in a Mental Arithmetic Task.

Self-efficacy is a well-known psychological resource, being positively associated with increased performance. Furthermore, results from field studies suggest a positive impact of self-efficacy on flow experience, which has not yet been tested experimentally. In this study, we manipulated self-efficacy by means of positive feedback and investigated whether self-efficacy serves as a mediator in the relationship between positive feedback and flow and in the relationship between positive feedback and performance. Our sample consisted of 102 participants (63 female, 39 male). The experimental group received positive feedback after completing 5 min of mental arithmetic tasks on a computer, whereas the control group received no feedback. A second session of a mental arithmetic task was then completed for 5 min. Mediation analyses confirmed that specific self-efficacy mediated a positive effect of positive feedback on flow as well as on both performance measures (quality and quantity) in a subsequent task. However, direct effects of feedback on flow and on performance were not significant, which suggests the presence of other mechanisms that remain to be investigated.