The research methodology that Jamie is using to study hyperactive children is called a case study.
A case study refers to a study of individual (s), especially for establishing a new phenomenon that does not occur often in the general population. It usually requires an up-close and in-depth look of a subject and it generally requires the use of observation and interviews. The results of the study tend to be more qualitative in nature, though they can also be a mixture of both quantitative and qualitative.