정신지체인의 인격발달 연구는 Zigler를 중심으로 연구 되어왔고, 그는 5가지 인격의 핵심이 되는 구성요소가 어떻게 일상 적응행동 또는 부적응 행동과 관련하는가를 설명하고 있다. 최근 분자유전학의 발달로 유전적 증후군(윌리암스 증후군, 취약 X증후군, 스미스마제니스 증후군, 프라더-윌리증후군)을 가진 사람들의 행동표현형과 인격 양식의 경향성을 탐색하여 이들의 인격 경향성을 Zigler의 인격 양식으로 분류해 보고 이를 통해 적절한 교육적 조치를 어떻게 할 수 있는지를 모색해보고자 하였다.본 연구를 통해서 밝힐 수 있었던 것은 첫째, 인격 양식에 따른 적응과 부적응의 요소를 밝힐 수 잇었다. 둘째, 유전적 증후군과 관련된 4가지 증후군의 행동표현형을 통해 인격 양식의 경향을 알 수 있었다. 마지막으로 각 경향성에 따른 교육적 방안을 모색할 수 있었다.

Zigler and Balla argued that the rigidity of the personality of children with mental retardation is not innate but stem from motivation related to social learning experience among them or between them and children with no disability. Owing to advance in genetics, it``s found that people with specific hereditary or etiologic syndromes have a tendency to have a particular personality or show specific pathological problems, and it``s required to take a genetic approach to personality research. The findings of the study showed that there were positive-reaction tendency and negative-reaction tendency in the five personality modes suggested by Zigler, and that it``s possible to connect two different research areas, personality and psychopathology. The genetic etiology was expected to open a new chapter for future personality studies, and molecular genetics made it clear that there were behavioral similarities among several syndromes including William``s Syndrome, Fragile X Syndrome, Simth-Magenis Syndrome and Parder-willi Syndrome. That made an attempt to combine them with personality mode, but more experimental research are called for in that regard. Educational intervention based on personality mode and more aggressive alternatives, including pharmacotherapy, cognitive restructuring and positive behavior support, were presented as a vehicle to improve personality disorder, but more experimental research efforts should be dedicated to this field as well.