Uma das principais áreas de pesquisa em Biologia de Sistemas refere-se à descoberta de redes biológicas a partir de conjuntos de dados de microarrays. Estas redes consistem de um grande número de genes cujos níveis de expressão afetam os outros genes de vários modos. Nesta tese, apresenta-se uma nova maneira de analisar os conjuntos de dados de microarrays, com base nos diferentes tipos de ciclos encontrados entre os genes das redes de co-expressão construídas com dados quantificados obtidos a partir dos microarrays. A entrada do método de análise é formada pelos dados brutos, um conjunto de genes de interesse (por exemplo, genes de uma via conhecida) e uma função (ativador ou inibidor) destes genes. A saída do método é um conjunto de ciclos. Um ciclo é um caminho fechado com todos os vértices (exceto o primeiro e o último) distintos. Graças à nova forma de encontrar relações entre os genes, é possível uma interpretação mais robusta das correlações dos genes, porque os ciclos estão associados a mecanismos de feedback, que são muito comuns em redes biológicas. A hipótese é que feedbacks negativos permitem encontrar relações entre os genes que podem ajudar a explicar a estabilidade do processo regulatório dentro da célula. Ciclos de feedback positivo, por outro lado, podem mostrar a quantidade de desequilíbrio de uma determinada célula em um determinado momento. A análise baseada em ciclos permite identificar a relação estequiométrica entre os genes da rede. Esta metodologia proporciona uma melhor compreensão da biologia do tumor. Portanto, as principais contribuições desta tese são: (i) um novo método de análise baseada em ciclos; (ii) um novo método de classificação; (iii) e, finalmente, aplicação dos métodos e a obtenção de resultados práticos. A metodologia proposta foi utilizada para analisar os genes de quatro redes fortemente relacionadas com o câncer - apoptose, glicólise, ciclo celular e NF B - em tecidos do tipo mais agressivo de tumor cerebral (Gliobastoma multiforme - GBM) e em tecidos cerebrais saudáveis. A maioria dos pacientes com GBM morrem em menos de um ano, essencialmente nenhum paciente tem sobrevivência a longo prazo, por isso estes tumores têm atraído atenção significativa. Os principais resultados nesta tese mostram que a relação estequiométrica entre genes envolvidos na apoptose, glicólise, ciclo celular e NF B está desequilibrada em amostras de GBM em comparação as amostras de controle. Este desequilíbrio pode ser medido e explicado pela identificação de um percentual maior de ciclos positivos nas redes das primeiras amostras. Esta conclusão ajuda a entender mais sobre a biologia deste tipo de tumor. O método de classificação baseado no ciclo proposto obteve as mesmas métricas de desempenho como uma rede neural, um método clássico de classificação. No entanto, o método proposto tem uma vantagem significativa em relação às redes neurais. O método de classificação proposto não só classifica as amostras, fornecendo diagnóstico, mas também explica porque as amostras foram classificadas de uma certa maneira em termos dos mecanismos de feedback que estão presentes/ausentes. Desta forma, o método fornece dicas para bioquímicos sobre possíveis experiências laboratoriais, bem como sobre potenciais genes alvo de terapias. / One of the main research areas in Systems Biology concerns the discovery of biological networks from microarray datasets. These networks consist of a great number of genes whose expression levels affect each other in various ways. We present a new way of analyzing microarray datasets, based on the different kind of cycles found among genes of the co-expression networks constructed using quantized data obtained from the microarrays. The input of the analysis method is formed by raw data, a set of interest genes (for example, genes from a known pathway) and a function (activator or inhibitor) of these genes. The output of the method is a set of cycles. A cycle is a closed walk, in which all vertices (except the first and last) are distinct. Thanks to the new way of finding relations among genes, a more robust interpretation of gene correlations is possible, because cycles are associated with feedback mechanisms that are very common in biological networks. Our hypothesis is that negative feedbacks allow finding relations among genes that may help explaining the stability of the regulatory process within the cell. Positive feedback cycles, on the other hand, may show the amount of imbalance of a certain cell in a given time. The cycle-based analysis allows identifying the stoichiometric relationship between the genes of the network. This methodology provides a better understanding of the biology of tumors. As a consequence, it may enable the development of more effective treatment therapies. Furthermore, cycles help differentiate, measure and explain the phenomena identified in healthy and diseased tissues. Cycles may also be used as a new method for classification of samples of a microarray (cancer diagnosis). Compared to other classification methods, cycle-based classification provides a richer explanation of the proposed classification, that can give hints on the possible therapies. Therefore, the main contributions of this thesis are: (i) a new cycle-based analysis method; (ii) a new microarray samples classification method; (iii) and, finally, application and achievement of practical results. We use the proposed methodology to analyze the genes of four networks closely related with cancer - apoptosis, glucolysis, cell cycle and NF B - in tissues of the most aggressive type of brain tumor (Gliobastoma multiforme – GBM) and in healthy tissues. Because most patients with GBMs die in less than a year, and essentially no patient has long-term survival, these tumors have drawn significant attention. Our main results show that the stoichiometric relationship between genes involved in apoptosis, glucolysis, cell cycle and NF B pathways is unbalanced in GBM samples versus control samples. This dysregulation can be measured and explained by the identification of a higher percentage of positive cycles in these networks. This conclusion helps to understand more about the biology of this tumor type. The proposed cycle-based classification method achieved the same performance metrics as a neural network, a classical classification method. However, our method has a significant advantage with respect to neural networks. The proposed classification method not only classifies samples, providing diagnosis, but also explains why samples were classified in a certain way in terms of the feedback mechanisms that are present/absent. This way, the method provides hints to biochemists about possible laboratory experiments, as well as on potential drug target genes.

Uma das principais áreas de pesquisa em Biologia de Sistemas refere-se à descoberta de redes biológicas a partir de conjuntos de dados de microarrays. Estas redes consistem de um grande número de genes cujos níveis de expressão afetam os outros genes de vários modos. Nesta tese, apresenta-se uma nova maneira de analisar os conjuntos de dados de microarrays, com base nos diferentes tipos de ciclos encontrados entre os genes das redes de co-expressão construídas com dados quantificados obtidos a partir dos microarrays. A entrada do método de análise é formada pelos dados brutos, um conjunto de genes de interesse (por exemplo, genes de uma via conhecida) e uma função (ativador ou inibidor) destes genes. A saída do método é um conjunto de ciclos. Um ciclo é um caminho fechado com todos os vértices (exceto o primeiro e o último) distintos. Graças à nova forma de encontrar relações entre os genes, é possível uma interpretação mais robusta das correlações dos genes, porque os ciclos estão associados a mecanismos de feedback, que são muito comuns em redes biológicas. A hipótese é que feedbacks negativos permitem encontrar relações entre os genes que podem ajudar a explicar a estabilidade do processo regulatório dentro da célula. Ciclos de feedback positivo, por outro lado, podem mostrar a quantidade de desequilíbrio de uma determinada célula em um determinado momento. A análise baseada em ciclos permite identificar a relação estequiométrica entre os genes da rede. Esta metodologia proporciona uma melhor compreensão da biologia do tumor. Portanto, as principais contribuições desta tese são: (i) um novo método de análise baseada em ciclos; (ii) um novo método de classificação; (iii) e, finalmente, aplicação dos métodos e a obtenção de resultados práticos. A metodologia proposta foi utilizada para analisar os genes de quatro redes fortemente relacionadas com o câncer - apoptose, glicólise, ciclo celular e NF B - em tecidos do tipo mais agressivo de tumor cerebral (Gliobastoma multiforme - GBM) e em tecidos cerebrais saudáveis. A maioria dos pacientes com GBM morrem em menos de um ano, essencialmente nenhum paciente tem sobrevivência a longo prazo, por isso estes tumores têm atraído atenção significativa. Os principais resultados nesta tese mostram que a relação estequiométrica entre genes envolvidos na apoptose, glicólise, ciclo celular e NF B está desequilibrada em amostras de GBM em comparação as amostras de controle. Este desequilíbrio pode ser medido e explicado pela identificação de um percentual maior de ciclos positivos nas redes das primeiras amostras. Esta conclusão ajuda a entender mais sobre a biologia deste tipo de tumor. O método de classificação baseado no ciclo proposto obteve as mesmas métricas de desempenho como uma rede neural, um método clássico de classificação. No entanto, o método proposto tem uma vantagem significativa em relação às redes neurais. O método de classificação proposto não só classifica as amostras, fornecendo diagnóstico, mas também explica porque as amostras foram classificadas de uma certa maneira em termos dos mecanismos de feedback que estão presentes/ausentes. Desta forma, o método fornece dicas para bioquímicos sobre possíveis experiências laboratoriais, bem como sobre potenciais genes alvo de terapias. / One of the main research areas in Systems Biology concerns the discovery of biological networks from microarray datasets. These networks consist of a great number of genes whose expression levels affect each other in various ways. We present a new way of analyzing microarray datasets, based on the different kind of cycles found among genes of the co-expression networks constructed using quantized data obtained from the microarrays. The input of the analysis method is formed by raw data, a set of interest genes (for example, genes from a known pathway) and a function (activator or inhibitor) of these genes. The output of the method is a set of cycles. A cycle is a closed walk, in which all vertices (except the first and last) are distinct. Thanks to the new way of finding relations among genes, a more robust interpretation of gene correlations is possible, because cycles are associated with feedback mechanisms that are very common in biological networks. Our hypothesis is that negative feedbacks allow finding relations among genes that may help explaining the stability of the regulatory process within the cell. Positive feedback cycles, on the other hand, may show the amount of imbalance of a certain cell in a given time. The cycle-based analysis allows identifying the stoichiometric relationship between the genes of the network. This methodology provides a better understanding of the biology of tumors. As a consequence, it may enable the development of more effective treatment therapies. Furthermore, cycles help differentiate, measure and explain the phenomena identified in healthy and diseased tissues. Cycles may also be used as a new method for classification of samples of a microarray (cancer diagnosis). Compared to other classification methods, cycle-based classification provides a richer explanation of the proposed classification, that can give hints on the possible therapies. Therefore, the main contributions of this thesis are: (i) a new cycle-based analysis method; (ii) a new microarray samples classification method; (iii) and, finally, application and achievement of practical results. We use the proposed methodology to analyze the genes of four networks closely related with cancer - apoptosis, glucolysis, cell cycle and NF B - in tissues of the most aggressive type of brain tumor (Gliobastoma multiforme – GBM) and in healthy tissues. Because most patients with GBMs die in less than a year, and essentially no patient has long-term survival, these tumors have drawn significant attention. Our main results show that the stoichiometric relationship between genes involved in apoptosis, glucolysis, cell cycle and NF B pathways is unbalanced in GBM samples versus control samples. This dysregulation can be measured and explained by the identification of a higher percentage of positive cycles in these networks. This conclusion helps to understand more about the biology of this tumor type. The proposed cycle-based classification method achieved the same performance metrics as a neural network, a classical classification method. However, our method has a significant advantage with respect to neural networks. The proposed classification method not only classifies samples, providing diagnosis, but also explains why samples were classified in a certain way in terms of the feedback mechanisms that are present/absent. This way, the method provides hints to biochemists about possible laboratory experiments, as well as on potential drug target genes.

Abstract Based on the sequential auction model of Kyle (1985) and embedded the formulation of positive feedback traders in De Long et al. (1990), our model formulates a recursive market game of insiders, noise traders, and market makers. In particular, the submitted demands of positive feedback inertial traders are influenced by previous own trading quantities. I prove the existence and uniqueness of a recursive linear equilibrium with positive feedback inertial trades. Further, the equilibrium calibrates that the strategies of insider and market makers are also influenced by positive feedback trades. Finally, we conduct a simulation analysis to get a price-volume pattern with some empirical interesting implications. Finally, this thesis takes trading strategies to trade the individual stock in TSEC. Although the market mechanism of TSEC has no market makers, it is still expected that these trading strategies are useful for traders which implies the information is filtrated by these trading strategies.

In everyday situations individuals make decisions. For example, a tourist usually chooses a crowded or recommended restaurant to have dinner. Perhaps it is an individual decision, but the observed pattern of decision-making is a collective phenomenon. Collective behaviour emerges from the local interactions that give rise to a complex pattern at the group level. In our example, the recommendations or simple copying the choices of others make a crowded restaurant even more crowded. The rules of interaction between individuals are important to study. Such studies should be complemented by biological experiments. Recent studies of collective phenomena in animal groups help us to understand these rules and develop mathematical models of collective behaviour. The most important communication mechanism is positive feedback between group members, which we observe in our example. In this thesis, we use a generic experimentally validated model of positive feedback to study collective decision-making. The first part of the thesis is based on the modelling of decision-making associated to the selection of feeding sites. This has been extensively studied for ants and slime moulds. The main contribution of our research is to demonstrate how such aspects as "irrationality", speed and quality of decisions can be modelled using differential equations. We study bifurcation phenomena and describe collective patterns above critical values of a bifurcation points in mathematical and biological terms. In the second part, we demonstrate how the primitive unicellular slime mould Physarum Polycephalum provides an easy test-bed for theoretical assumptions and model predictions about decision-making. We study its searching strategies and model decision-making associated to the selection of food options. We also consider the aggregation model to investigate the fractal structure of Physarum Polycephalum plasmodia. / <p>Fel serie i tryckt bok /Wrong series in the printed book</p>

A simple integrated assessment framework that gives rules for the optimal carbon price, transition to the carbon-free era and stranded carbon assets is presented, which highlights the ethical, economic, geophysical and political drivers of optimal climate policy. For the ethics we discuss the role of intergenerational inequality aversion and the discount rate, where we show the importance of lower discount rates for appraisal of longer run benefit and of policy makers using lower discount rates than private agents. The economics depends on the costs and rates of technical progress in production of fossil fuel, its substitute renewable energies and sequestration. The geophysics depends on the permanent and transient components of atmospheric carbon and the relatively fast temperature response, and we allow for positive feedbacks. The politics stems from international free-rider problems in absence of a global climate deal. We show how results change if different assumptions are made about each of the drivers of climate policy. Our main objective is to offer an easy back-on-the-envelope analysis, which can be used for teaching and communication with policy makers. / Series: Ecological Economic Papers

A simple integrated assessment framework that gives rules for the optimal carbon price, transition to the carbon-free era and stranded carbon assets is presented, which highlights the ethical, economic, geophysical and political drivers of optimal climate policy. For the ethics we discuss the role of intergenerational inequality aversion and the discount rate, where we show the importance of lower discount rates for appraisal of longer run benefit and of policy makers using lower discount rates than private agents. The economics depends on the costs and rates of technical progress in production of fossil fuel, its substitute renewable energies and sequestration. The geophysics depends on the permanent and transient components of atmospheric carbon and the relatively fast temperature response, and we allow for positive feedbacks. The politics stems from international free-rider problems in absence of a global climate deal. We show how results change if different assumptions are made about each of the drivers of climate policy. Our main objective is to offer an easy back-on-the-envelope analysis, which can be used for teaching and communication with policy makers.

<p>Syfte och frågeställningar</p><p>Syftet med denna studie är att undersöka om det går att påverka ungdomars fysiska prestation med hjälp av positiv feedback. De olika frågeställningarna som utvecklats utifrån detta syfte ämnar ta reda på skillnaden i resultaten för de tester utförda med, respektive utan positiv feedback. Andra variabler som skillnad i slutpuls, om den positiva feedbacken gör större inverkan vid statiska styrkeövningar jämfört med dynamiska, undersöks också.</p><p>Metod</p><p>För att kunna besvara frågeställningarna har en experimentell crossover designad studie genomförts på en grupp bestående av 21 stycken idrottsaktiva pojkar födda 1994. De tester som genomfördes var Tid till utmattning på löpband, Belly-back-, Armhang-, och ett Handgriptest. Ett förtest genomfördes med alla försökspersoner, vid det tillfället fick deltagarna möjlighet att prova testerna. Därefter delades ungdomarna in i två grupper, Grupp A och Grupp B. Grupp A mottog feedback vid första tillfället men inte vid andra. Grupp B mottog ingen feedback vid första tillfället men däremot vid det andra tillfället. Försökspersonerna visste inte om syftet med studien under studiens gång. Testresultaten bearbetades sedan i SPSS 15.0 för windows.</p><p>Resultat</p><p>Resultaten visar i samtliga fall förutom vid testen för handgrip på en signifikant förbättring i testresultat vid de tester som genomfördes med positiv feedback. Störst förbättring var det vid de övningar som testade statisk uthållig styrka (Belly-back och Armhang), den största procentuella förbättringen uppmättes i Armhang (35%) och den största skillnaden i tid uppmättes i Belly-back (31,0 s). Ingen signifikant skillnad kunde ses mellan Grupp A och Grupp B.</p><p>Slutsats</p><p>Denna studie påvisar liksom tidigare forskning att positiv feedback kan förbättra resultatet vid fysiskt arbete. En intressant del av arbetet är att effekten av den positiva feedbacken var mycket större vid statsikt arbete än vid dynamiskt arbete. Det har dock inte bedrivits mycket forskning på ungdomar inom detta område. Det skulle vara intressant att vidareutveckla denna typ av studie på en större population där man även kan kartlägga ungdomarnas bakgrund för att kunna koppla mottagandet av feedback till en viss personlighetstyp.</p> / <p>Aim</p><p>The aim in this study is to examine if it is possible to affect the physical performance in adolescence with positive feedback. The different questions asked on the basis of this aim, is intended to explore the difference in the results for the tests made with, respectively without positive feedback. Other objects, like difference in end pulse, if the positive feedback has a larger effect when performing statical strenght compared to dynamic strenght, is also examined. B.F Skinners theories of removemet of the positiv feedback is tested.</p><p>Method</p><p>To answer the questions asked, a exprementell cross-over designed study was carried out on a group of 21 boys born in 1994, acitve in sports. The tests made in the study were Time to exhaution on threadmill, Belly-Back, Armhang, and Handgrip. A pretest was exucuted with all subjects, on that occasion the subjects had the opportunity to try all tests they later would perform. Thereafter the adolescence were divided into two groups, Group A and Group B. Group A recieved feedback in the first session but not in the second one. Group B did not recieve feedback in the first test session, instead they recieved it in the second session. The subjects did not know the purpose with the study during the time for the study.</p><p>Results</p><p>In all the tests excluding the one for handstrenght, the results shows a significant improvement in the tests performed with positive feedback. The largest improvements were seen in the tests for static endurance strenght (Belly-back and Armhang), the largest difference in percent was seen in the Armhang test (35%) and the largest difference in time was seen in the Belly-back test (31,0 s). No significant difference could be seen when Group A and B were compared.</p><p>Conclusions</p><p>This study indicates, like the previous research, that positive feedback may improve the results in physical performence. An interesting part of this work is the observation of the larger effect of the positive feedback when performing static endurance strenght compared to tests for dynamic endurance. Alltough, the research on adolescence in this particular topic is not widespread. It would be highly interesting to develope this kind of study on a larger population and describe the background for the subjects to better find out how their different personalitys effect their response to the positive feedback.</p>

Syfte och frågeställningar Syftet med denna studie är att undersöka om det går att påverka ungdomars fysiska prestation med hjälp av positiv feedback. De olika frågeställningarna som utvecklats utifrån detta syfte ämnar ta reda på skillnaden i resultaten för de tester utförda med, respektive utan positiv feedback. Andra variabler som skillnad i slutpuls, om den positiva feedbacken gör större inverkan vid statiska styrkeövningar jämfört med dynamiska, undersöks också. Metod För att kunna besvara frågeställningarna har en experimentell crossover designad studie genomförts på en grupp bestående av 21 stycken idrottsaktiva pojkar födda 1994. De tester som genomfördes var Tid till utmattning på löpband, Belly-back-, Armhang-, och ett Handgriptest. Ett förtest genomfördes med alla försökspersoner, vid det tillfället fick deltagarna möjlighet att prova testerna. Därefter delades ungdomarna in i två grupper, Grupp A och Grupp B. Grupp A mottog feedback vid första tillfället men inte vid andra. Grupp B mottog ingen feedback vid första tillfället men däremot vid det andra tillfället. Försökspersonerna visste inte om syftet med studien under studiens gång. Testresultaten bearbetades sedan i SPSS 15.0 för windows. Resultat Resultaten visar i samtliga fall förutom vid testen för handgrip på en signifikant förbättring i testresultat vid de tester som genomfördes med positiv feedback. Störst förbättring var det vid de övningar som testade statisk uthållig styrka (Belly-back och Armhang), den största procentuella förbättringen uppmättes i Armhang (35%) och den största skillnaden i tid uppmättes i Belly-back (31,0 s). Ingen signifikant skillnad kunde ses mellan Grupp A och Grupp B. Slutsats Denna studie påvisar liksom tidigare forskning att positiv feedback kan förbättra resultatet vid fysiskt arbete. En intressant del av arbetet är att effekten av den positiva feedbacken var mycket större vid statsikt arbete än vid dynamiskt arbete. Det har dock inte bedrivits mycket forskning på ungdomar inom detta område. Det skulle vara intressant att vidareutveckla denna typ av studie på en större population där man även kan kartlägga ungdomarnas bakgrund för att kunna koppla mottagandet av feedback till en viss personlighetstyp. / Aim The aim in this study is to examine if it is possible to affect the physical performance in adolescence with positive feedback. The different questions asked on the basis of this aim, is intended to explore the difference in the results for the tests made with, respectively without positive feedback. Other objects, like difference in end pulse, if the positive feedback has a larger effect when performing statical strenght compared to dynamic strenght, is also examined. B.F Skinners theories of removemet of the positiv feedback is tested. Method To answer the questions asked, a exprementell cross-over designed study was carried out on a group of 21 boys born in 1994, acitve in sports. The tests made in the study were Time to exhaution on threadmill, Belly-Back, Armhang, and Handgrip. A pretest was exucuted with all subjects, on that occasion the subjects had the opportunity to try all tests they later would perform. Thereafter the adolescence were divided into two groups, Group A and Group B. Group A recieved feedback in the first session but not in the second one. Group B did not recieve feedback in the first test session, instead they recieved it in the second session. The subjects did not know the purpose with the study during the time for the study. Results In all the tests excluding the one for handstrenght, the results shows a significant improvement in the tests performed with positive feedback. The largest improvements were seen in the tests for static endurance strenght (Belly-back and Armhang), the largest difference in percent was seen in the Armhang test (35%) and the largest difference in time was seen in the Belly-back test (31,0 s). No significant difference could be seen when Group A and B were compared. Conclusions This study indicates, like the previous research, that positive feedback may improve the results in physical performence. An interesting part of this work is the observation of the larger effect of the positive feedback when performing static endurance strenght compared to tests for dynamic endurance. Alltough, the research on adolescence in this particular topic is not widespread. It would be highly interesting to develope this kind of study on a larger population and describe the background for the subjects to better find out how their different personalitys effect their response to the positive feedback.

Collective decision making can be seen as a means of designing and understanding swarm robotics systems. While decision-making is generally conceived as the cognitive ability of individual agents to select a belief based only on their preferences and available information, collective decision making is a decentralized cognitive process, whereby an ensemble of agents gathers, shares, and processes information as a single organism and makes a choice that is not attributable to any of its individuals. A principled selection of the rules governing this cognitive process allows the designer to define, shape, and foresee the dynamics of the swarm.We begin this monograph by introducing the reader to the topic of collective decision making. We focus on artificial systems for discrete consensus achievement and review the literature of swarm robotics. In this endeavor, we formalize the best-of-n problem—a generalization of the logic underlying several cognitive problems—and define a taxonomy of its possible variants that are of interest for the design of robot swarms. By leveraging on this understanding, we identify the building-blocks that are essential to achieve a collective decision addressing the best-of-n problem: option exploration, opinion dissemination, modulation of positive feedback, and individual decision-making mechanism. We show how a modular perspective of a collective decision-making strategy allows for the systematic modeling of the resulting swarm performance. In doing so, we put forward a modular and model-driven design methodology that allows the designer to study the dynamics of a swarm at different level of abstractions. Successively, we employ the proposed design methodology to derive and to study different collective decision-making strategies for the best-of-n problem. We show how the designed strategies can be readily applied to different real-world scenarios by performing two series of robot experiments. In the first series, we use a swarm of 100 robots to tackle a site-selection scenario; in the second series, we show instead how the same strategies apply to a collective perception scenario. We conclude with a discussion of our research contributions and provide futuredirection of research. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

Formal dialogues between an employee and a manager have long existed as a tool to achieve organizational goals and to develop employees as well as the organization. Development requires the exchange of feedback between employees and managers which is considered as one of the most important parts of the performance appraisal talk. Despite the purpose of the talk, previous research proves a dissatisfaction with the talks among the employees and an uncertainty with its practical usefulness. It is of significance that employees have a positive attitude towards the performance appraisal talk and its use in order to create favorable effects for the organization. Therefore, this study aims to understand employees and managers perception of the performance appraisal talk and to form an understanding with the parties receptivity towards feedback during the talks.   The purpose of this study has been fulfilled through a total of eight interviews with employees and managers in Handelsbanken.   The result of the interviews show that all respondents have a positive attitude towards performance appraisal talks, and both managers and employees agreed that the talk is of high significance. The purpose of the talk is to notice, develop and support the employees, create common goals and to exchange feedback between the parties. The interviews indicate that all respondents are receptive towards both positive and negative feedback during the performance appraisal talk. According to the managers and employees, the receptivity to feedback depends on the individual and the current situation. Positive feedback is preferred and feels easier to receive and process, but at the same time, negative feedback is also regarded as needful. / Formella samtal mellan medarbetare och chef har länge existerat i organisationer som ett verktyg för att nå satta mål i organisationen och bana väg för utveckling av både medarbetare och organisation. Utveckling förutsätter att feedback utbyts mellan parterna vilket bedöms som ett av samtalets viktigaste funktioner. Trots samtalets syfte, påvisar tidigare forskning attdet finns tveksamhet och missnöje bland anställda kring samtalets praktiska användbarhet. Det är av betydelse att anställda har en positiv inställning till medarbetarsamtal och dess funktion för att det ska skapa gynnsamma effekter för organisationen. Studien syftardärmed till att förstå medarbetares respektive chefers uppfattning om medarbetarsamtal samt skapa förståelse för parternas mottaglighet för feedback i samtalen. Forskningsmetoden följer en kvalitativ ansats och en fallstudiehar genomförts på olika kontor i Handelsbanken. För att uppnå studiens syfte har totalt 8 semi-strukturerade intervjuer genomförts med chefer och medarbetare på kontorsnivå. Resultatet visaratt samtligarespondenter har en positiv inställning till medarbetarsamtal på arbetsplatsen och både chefer och medarbetare var ense om att samtalet är betydelsefullt. Resultatet tyder på att medarbetarsamtalet handlar om att uppmärksamma, utveckla och stödja medarbetarna. Samtalet syftar även till att skapa en gemensam syn kring mål samtattförmedla feedback mellan chef och medarbetare. Samtliga respondenteri studienär mottagliga för både positiv och negativ feedback i samband med samtalen. Enligt både chefs-och medarbetarperspektivet är mottagligheten för feedback beroende av individen och situationen. Positiv feedback föredras och upplevs vara lättare att motta samt bearbeta, men samtidigt anses det behövligt att även motta negativ feedback.