Down Syndrome Cognitive Development: New Research Shows Promise for Adult Learning and Independence | Bar-Ilan University Study

A new study challenges previous assumptions about the cognitive potential of adults with non-specific intellectual disability (NSID), particularly those with Down syndrome (DS). Researchers from Bar-Ilan University, Ariel University, and Levinsky College of Education examined 340 adolescents (16-21) and adults (22-45) to compare their crystallized intelligence (acquired knowledge) and fluid intelligence (problem-solving skills). Published in Scientific Reports, the cross-sectional study revealed encouraging findings about cognitive growth and development in these individuals, suggesting continued cognitive development well into adulthood.

Among the key findings:
• Adults with intellectual disabilities demonstrated higher cognitive performance compared to adolescents across three key intelligence tests – Vocabulary, Similarities, and Block Design of the Wechsler Adult Intelligence Test — supporting the Compensation Age Theory (Lifshitz, 2020), which suggests the continued potential for learning and development into the mid-40s.

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• Fluid intelligence differences: Participants with DS performed better on tasks measuring fluid intelligence, including Block Design and Raven Matrix tests, involving visual-spatial reasoning and problem-solving abilities compared to those with NSID.

• Crystallized intelligence differences: Individuals with NSID scored higher on the Vocabulary test, a measure of crystallized intelligence, compared to those with DS.

• No difference in verbal reasoning: In the Similarities test, a measure of verbal reasoning, no difference was found between the two groups, suggesting that verbal abilities in individuals with DS may be less impaired than previously thought.

• Distinct cognitive profiles: Graph analysis revealed distinct cognitive networks between the groups. Surprisingly, participants with DS showed more integrated connections between crystallized and fluid intelligence, especially in adulthood, while adults with NSID displayed more fragmented cognitive connections.

Adults with Down syndrome (DS) showed relatively stronger verbal abilities and more coherent connections between fluid and crystallized intelligence, suggesting a more cohesive cognitive and neurological profile. While typical populations show a strong correlation between these two types of intelligence across the lifespan (meaning higher scores in one tend to correlate with higher scores in the other), this study found similar correlations only in adults with DS (ages 22-45), not in adults with NSID. This suggests that the relationship between fluid and crystallized intelligence in adults with DS mirrors that of the typical population in the same age range.

“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 are with 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.