This thesis examines determinacy and E-stability of economic policy in monetary union models. Monetary policy takes the form of either a contemporaneous or a forecast based interest rate rule, while fiscal policy follows a contemporaneous government spending rule. In the absence of asymmetries, the results from the closed economy literature on learning are retained. However, when introducing asymmetries into monetary union frameworks, the determinacy and E-stability conditions for economic policy differ from both the closed and open economy cases. We find that a monetary union with heterogeneous price rigidities is more likely to be determinate and E-stable. Specifically, the Taylor principle, a key stability condition for the closed economy, is now relaxed. Furthermore, an interest rate rule that stabilizes the terms of trade in addition to output and inflation, is more likely to induce determinacy and local stability under RLS learning. If monetary policy is sufficiently aggressive in stabilizing the terms of trade, then determinacy and E-stability of the union economy can be achieved without direct stabilization of output and inflation. A fiscal policy rule that supports demand for domestic goods following a shock to competitiveness, can destabilize the union economy regardless of the interest rate rule employed by the union central bank. In this case, determinacy and E-stability conditions have to be simultaneously and independently met by both fiscal and monetary policy for the union economy to be stable. When fiscal policy instead stabilizes domestic output gaps while monetary policy stabilizes union output and inflation, fiscal policy directly affects the stability of monetary policy. A contemporaneous monetary policy rule has to be more aggressive to satisfy the Taylor principle, the more aggressive fiscal policy is. On the other hand, when monetary policy is forward looking, an aggressive fiscal policy rule can help induce determinacy.

Cette thèse analyse le rôle de l’apprentissage dans deux cadres de modélisation distincts. Dans le cas dunouveau modèle canonique avec apprentissage adaptatif, les caractéristiques les plus marquantes des dynamiquesd’apprentissage concernent la capacité des règles de politique monétaire à assurer la convergencevers l’équilibre en anticipations rationnelles. Le mécanisme de transmission de la politique monétaire estcelui de l’effet de substitution associé au canal de la consommation. Dans le cas d’un modèle multi-agentsqui relâche des hypothèses restrictives du nouveau modèle canonique, tout en restant structurellementproche de celui-ci, les variables agrégées évoluent à bonne distance de cet équilibre, et on observe desdynamiques nettement différentes. La politique monétaire influence les variables agrégées de manièremarginale via l’effet de revenu du canal de la consommation. En présence d’un processus d’apprentissagesocial évolutionnaire, l’économie converge vers un faible niveau d’activité économique. L’introductiond’un processus caractérisé par le fait que les agents apprennent individuellement à l’aide de leurs modèlesmentaux atténue le caractère dépressif des dynamiques d’apprentissage. Ces différences entre les deuxcadres de modélisation démontrent la difficulté de généraliser les résultats du nouveau modèle canonique. / This thesis analyses the role of learning in two different modelling frameworks. In the new canonicalmodel with adaptive learning, the most remarkable characteristics of the learning dynamics deal withthe capacity of monetary policy rules to guaranty convergence to the rational expectations equilibrium.The transmission mechanism of the monetary policy is based on the substitution effect associated to theconsumption channel. In the case of an agent-based model which relaxes some restrictive assumptionsof the new canonical model - but is endowed with a similar structure - aggregate variables evolve atsome distance from the rational expectations equilibrium. Monetary policy has a marginal impact onthe agregated variables via the wealth effect of the consumption channel. When agents learn accordingto an evolutionnary social learning process, the economy converges to regions of low economic activity.The introduction of a process where agents learn individually by using their mental models induces lessdepressive learning dynamics. These differences between the two modelling frameworks show that thegeneralisation of the results of the new canonical model is not easy to achieve.