A new study has revealed encouraging findings about cognitive growth and development in adults with non-specific intellectual disability (NSID), especially those with Down syndrome (DS), and challenges previous assumptions about cognitive potential of individuals with Down syndrome.
The cross-sectional study examined 340 individuals across adolescent (ages 16-21) and adult (ages 22-45) groups, comparing crystallized intelligence (which involves acquired knowledge, language, and facts) and fluid intelligence (which involves problem-solving and reasoning ability).
The results, recently published in the journal Scientific Reports, provide a comprehensive picture of cognitive development patterns in these populations and new hope for continued cognitive development well into adulthood.
Among the key findings:
The relative strength in verbal ability and the more coherent connections between the two types of intelligence in participants with DS indicate a more cognitively and neurologically coherent profile in DS etiology, especially in adulthood.
In a typical population, scientists examined the association between fluid and crystallized intelligence throughout the life span. Higher correlations between the two suggested that participants who display higher scores in one type of intelligence also show higher scores in the other.
Surprisingly, in the current study, the interconnections between the two types of intelligence are consistent with the correlations between the two types of intelligence that were found in the typical population in the same age period (22-45), but only in adults with DS and not those with NSID.
"Our findings indicate relative strength and compensation of cognitive abilities in visual spatial areas, and even in language and verbal abilities in a clear diagnostic etiology such as DS, especially in adulthood, compared to unclear genetic etiologies such as NSID," asserts Prof. Hefziba Lifshitz, of the Faculty of Education at Bar-Ilan University, the lead author of the study.
"We now have evidence that cognitive development continues well into adulthood for these populations. These findings have significant implications for educational and support services," adds Lifshitz, who collaborated with Dr. Roi Yozevitch from the Department of Computer Science at Ariel University and Dr. Shlomit Shnitzer-Meirovich from Levinsky College of Education.
The research confirms that educational and developmental programs should be extended beyond adolescence, as adults with both DS and NSID demonstrate capacity for continued cognitive growth. This is particularly relevant as life expectancy for individuals with intellectual disabilities continues to increase, with many now living beyond 80 years.
In July 2024, six students enrolled in the Empowerment Project at Bar-Ilan University's Faculty of Education became the first ever adult cohort with Intellectual Disabilities (ID) in Israel to receive their bachelor's degree. Two of them have DS. The Empowerment Project, a first-of-its-kind program established by Prof. Lifshitz is based on her Compensation Age Theory, which postulates that chronological age, as opposed to mental age, plays an important role in determining the cognitive ability of adults with intellectual disability. The current study confirmed this postulation more strongly in adults with DS.
The findings of this study open new avenues for research and development of targeted interventions and educational programs specifically designed for adults with intellectual disabilities, potentially improving long-term outcomes and quality of life for these individuals.