The aim of this chapter is to describe the cognitive abilities deployed on agents and multi-agent systems by using examples from applications carried out by the authors. Particularly, the following agent abilities are reviewed: problem solving, memory, decision making and learning capabilities. These abilities, which involve most of the research done in Artificial Intelligence during decades of dealing with isolated agents, are revised in order to incorporate the interaction of agents in a multi-agent environment. The results of incorporating such capabilities to agents are the enhancement of the generality and flexibility of the systems
