The study of current research on competence emphasizes three main elements. First, there are many definitions of competence which correspond to various conceptions. Yet, the literature achieves some kind of consensus on competence: it is linked to action, is the goal-oriented ability to cope with certain tasks (or a more or less large class of tasks) in a given context, and consists of such elements as knowledge, functional competence and behavioural competencies. Third, the components of competence are not defined following a psychological model based on the processes involved in performing and regulating any activity. However, psychology offers several theoretical frameworks and notions useful to study the concept of competence. One of the aims of our paper is to review some psychological approaches and sum them up to form a model of competence we call maddec (model of dynamic analysis to describe and assess competencies). This model is based on the following concepts: schemes, as analyzed by G?rard?Vergnaud (1990), proactive and retroactive controls, and instrumental activity. We distinguish three types of retroactive controls: short-term loops (or productive loops), long-term loops (or constructive loops), and scheme changes (integrative loops). Two empirical studies are mentioned to show how this model can be used to describe and assess competencies. The first example shows how you can pass from an occupational framework to a competence framework. We prove how useful the data collected are to design a training method. The second example indicates how the model can identify qualitative and quantitative differences in the workers? professional competencies in a tyre company according to their work experience (short or long). We finally offer a mentoring model we call madic (model to help individuals to develop their competencies). It derives from the competence model we present and aims to more systematically analyze or design training initiatives to develop professional or academic competencies.