Feuerstein elaborated new methods of evaluation as well as new teaching tools, known today as dynamic assessment. The cognitive map describes the mental act in terms of several parameters that permit an analysis and interpretation of a subject's performance by locating specific problem areas and producing changes in corresponding dimensions. The manipulation of these parameters becomes highly important in the subject-examiner interaction, by helping the examiner to form and validate hypotheses regarding the subject's performance difficulties. Some children who were considered un-teachable were eventually accepted at normal school and studied successfully.