This study examines the evidence for the effectiveness of adaptive learning and the satisfaction level of students when using this type of learning. It first analyses the different classifications of adaptive learning systems existing in the literature, to focus later on describing some adaptive and intelligent e-learning systems, mainly those included in the groups of Intelligent Tutoring Systems (ITS), Adaptive Hypermedia Systems (AHS) and Intelligent Collaborative Learning systems. Next, the Effect Size (ES) tool is adopted as a standard way to compare the results of one pedagogical experiment to another. ES is used to analyze the effectiveness of some of the systems previously described, in order to demonstrate that adaptive learning can provide significant improvements in the learning process of students. Secondly, the learners' opinion is analyzed in order to estimate their satisfaction and to know their preferred mode of studying. Finally, a number of conclusions and future trends are discussed.
