Volume 18, Issue 4, 1970
The Dynamics of Intellectual Development in Individuals With Complete and Incomplete Trisomy of Chromosomes Group G in the Cariotype
The aim of the present article is to ascertain whether the Mental Age of a whole group of persons with Down’s Syndrome as well as each individual reared in the home rises systematically with chronological age from the age of 1 yr. to that of 20 yrs. and more; or that, from the ages of 12 to 16 years, a decisive retardation in the mental development occurs,- as certain studies tend to suggest. Furthermore, this paper displays the solution to the problem whether there exists a difference between the dynamics of intellectual development of the entire group and that of individual persons with complete and incomplete trisomy of chromosomes group G.
The intellectual development was measured by means of the Psyche Cattell Infant Intelligence Scale and/or Stanford-Binet Intelligence Scale (1937), form L, whereas social maturity by means of E. Doll’s Vineland Social Maturity Scale. The conventional I.Q.s. scores were converted into Deviation I.Q.s. Furthermore, the data acquired from all interviews, as well as observations and results from medical examinations, were seriously taken into consideration.
The results of this research were based on a sample of 165 persons of ages 7 months to 31 years, who reside in the home. The persons were tested 625 times, by means of the Psyche Cattell Infant Intelligence Scale and/or Stanford-Binet Intelligence Scale (1937). 58.2% were of the male sex and 41.8% were females. Among 165 persons: in 4.9% was diagnosed a mild mental deficiency, 50.3% a moderate one, 39.4% — severe mental deficiency. A profound mental deficiency was detected in 5.4% of the cases. From among those examined, 76 persons were submitted to cytogenetic tests. Using peripheral blood culture, according to Moorhead's method modified by Lejeune, partial trisomia of chromosomes Gx in the cariotype was encountered in 10.9% children with Down syndrome, in 84.3% were discovered to have complete trisomy of chromosome G1. In 2.6% appeared a mosaicism of type 46/47. Among 2.6% of children (siblings) was detected a translocation of type G/D. These cytogenetic tests were undertaken by A. Dobrzańska, M. D.
The (results based on a sample of 165 persons which were put to a series of 625 tests seem to indicate:
1. That the Mental Age related to an entire group of persons progresses in a rather systematic manner from one Chronological Age to another, namely from the age of 7 months to that of 20 yrs. and 6 months, and even above, calls for further investigations based on samples consisting of persons from an older C. A. group whose M. A. would be systematically measured during a period of several years.
2. That the Mental Age of different individuals increases more or less systematically from one age (C. A.) to another, for only in 2.4% of the cases a definite retardation of intellectual development was detected. Of these, 0.6% suffered a temporary retardation whereas 1.8% a permanent one. This retardation in mental development is accompanied by an additional factor which tends to severely harm the cortex, attaining the highest possible degree of mental development, as well as by a change of educational environment for a less advantageous one.
3. That the average I.Q.s hover more or less at the sanie level in the light of researches pursued at the chronological age level of 10 months to 20 yrs. and 6 months.
4. A close analysis of the I.Q.s of several particular persons indicates that only in particular cases appears a statistically significant lowering of the I.Q.s (among 7.9%). In the majority of cases (73.9), the I.Q.s are not subject to a significant change during a period of 4 yrs. and 2 months for this was the average amount of time between the first and last testing of the whole group of persons, Nevertheless, in 18.2% of the individuals, one can ascertain a significant improvement — and in 2.5% of these an even considerable one.
5. In the light of author’s own investigations it seems unfair to slate that between the ages of 12 to 16 years, the Mental Age (mental development) of all Mongoloids is arrested. Neither retardation nor dementia was revealed in the whole group of examined persons, If certain cases revealing retardation in the mental development do appear, this rarely comes about 2.4%. Even in individual cases dementia has not been detected.
6. Research conducted within a group of persons with complete trisomy (29 persons tested 159 times), and those with incomplete1 (partial) trisomy (8 persons tested 49 times) seems to indicate that an individual with incomplete trisomy possesses a higher I.Q. whereas his Mental Age increases faster when compared to individuals with complete trisomy of chromosome G1 in cariotype (see diagrams 4, 5 and 6). This equally affects both examined groups. These conclusions nevertheless require a confirmation based on more substantial material (more persons).