Down’s Syndrome cognitive development extends into adulthood, study shows
An Israeli study has demonstrated that people with Down’s Syndrome continue to have cognitive growth into adulthood, overturning widespread belief that their intellectual growth plateaus during the teen years.
Bar-Ilan University Photo: Yossi Zeliger/TPS-IL
The findings point scientists in the direction of extended educational programs for individuals with Down’s and similar disabilities.
“We now have evidence that cognitive development continues well into adulthood for these populations. These findings have significant implications for educational and support services,” said Prof. Hefziba Lifshitz, of Bar-Ilan University’s Faculty of Education, the study’s lead author.
“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 (Down’s Syndrome), especially in adulthood, compared to unclear genetic etiologies such as NSID (non-specific intellectual disability),” she explained.
NSID refers to intellectual disabilities that do not have a clearly defined or specific genetic, medical, or environmental cause.
Down’s Syndrome is caused by a genetic condition called trisomy 21, which occurs when an individual has an extra copy of a specific chromosome. Individuals with Down syndrome experience a wide range of cognitive impairments, including delays in intellectual development. However, some individuals may have only mild intellectual disabilities, while others may have moderate to severe impairments. The general nature of the developmental delay makes it difficult to categorize strictly under more defined intellectual disability diagnoses.
The study, conducted by researchers from Bar-Ilan University, Ariel University and the Levinsky College of Education, was recently published in the peer-reviewed journal, Scientific Reports. It focused on two types of intelligence: crystallized intelligence (acquired knowledge, language, and facts) and fluid intelligence (problem-solving and reasoning). They split 340 participants into adolescent (ages 16-21) and adult (ages 22-45) groups.
The research revealed that adults with intellectual disabilities, including DS, demonstrated superior cognitive performance compared to adolescents in tests such as Vocabulary, Similarities, and Block Design from the Wechsler Adult Intelligence Test. This supports the Compensation Age Theory, proposed by Prof. Hefziba Lifshitz, which posits that cognitive development continues into the mid-40s.
Participants with DS outperformed those with NSID in fluid intelligence tests, such as Block Design and Raven Matrix, which measure visual-spatial reasoning and problem-solving abilities. However, individuals with NSID showed higher scores on Vocabulary tests, indicating greater proficiency in crystallized intelligence compared to their DS counterparts. In the Similarities test, which assesses verbal reasoning, no significant difference was found between the two groups, suggesting less impairment in verbal abilities for individuals with DS than previously assumed.
Graph analysis further revealed distinct patterns of cognitive connectivity. Adults with DS exhibited more integrated connections between crystallized and fluid intelligence, resembling patterns observed in neurotypical populations. In contrast, participants with NSID displayed more fragmented cognitive networks.
In July, six students enrolled in the Empowerment Project at Bar-Ilan University’s Faculty of Education became the first cohort of adults with intellectual disabilities in Israel to earn bachelor’s degrees. Among them were two individuals with DS. The Empowerment Project, founded by Prof. Lifshitz, is rooted in her Compensation Age Theory, which emphasizes the role of chronological age over mental age in determining cognitive ability in adults with intellectual disabilities.
