Scientists to unravel trust in intellectual disability

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria : Group of Down Syndrom patients * Complete chromosomal trisomy of the 21st chromosome confirmed by karyotype analysis * Aged 13 to 29 (chronological age) * French as their native language * Having signed an informed consent form and/or whose legal guardians/patient representatives have signed the informed consent form * Affiliated with the French health insurance system (social security) or whose legal guardians are affiliated with the French health insurance system Group of X-Fragile Syndrome * Complete mutation of the FMR1 gene by molecular analysis (more than 200 CGG triplet repeats) * Aged between 13 and 29 (chronological age) * Native French speakers * Having signed an informed consent form and/or whose legal guardians/patient representatives have signed the informed consent form * Affiliated with the French health insurance system (social security) or whose legal guardians are affiliated with the French health insurance system Group of chronological age-matched control * Aged between 13 and 29 * Native French speakers. * Having signed an informed consent form and/or whose legal guardians/patient representatives have signed the informed consent form * Affiliated with the French health insurance system (social security) or whose legal guardians are affiliated with the French health insurance system Group of mental age-matched control * Aged between 3 and 9 * Native French speakers. * Whose legal guardians/patient representatives have signed the informed consent form * Affiliated with the French health insurance system (social security) or whose legal guardians are affiliated with the French health insurance system Exclusion Criteria: Groups of Down Syndrom and X-Fragiles patients * Inability to understand tasks * Significant brain malformation * Uncontrolled epilepsy * Significant hearing impairment * Uncorrected visual impairment * Refusal of the subject and/or legal guardians/representative of the subject to be informed of any abnormalities detected during the neuropsychological assessment. * Subject participating in another interventional study with an exclusion period still ongoing at the time of pre-inclusion. Regarding the neuroimaging (MRI) study: * Having a contraindication to MRI examination (people using a pacemaker or insulin pump, people with metal prostheses or intracerebral clips, people with metal fragments in their eyes, as well as claustrophobic subjects). A comprehensive list of contraindications is provided in Appendix 5. * Inability to perform the MRI without anaesthesia. * Refusal by the subject and/or those exercising parental authority/the subject's representative to be informed of any abnormalities detected during the MRI. Groups of typical development persons (chronological age-matched and mental age-matched) * Known acquired neurological disorders, including epilepsy. * History of head trauma requiring hospitalisation. * Known psychiatric disorders. * Birth complications requiring admission to a neonatal intensive care unit or prematurity of less than 35 weeks. * Ongoing treatment with drugs affecting the central nervous system. * Significant hearing impairment * Uncorrected visual impairment * Repeating a school year * Learning disorders requiring rehabilitation (speech therapy, psychomotor therapy or orthoptics) for more than one year. * Refusal of the subject and/or legal guardians/representative of the subject to be informed of any abnormalities detected during the neuropsychological assessment. * Subject participating in another interventional study with an exclusion period still ongoing at the time of pre-inclusion. Regarding the neuroimaging (MRI) study (only for chronological age-matched group): * Having a contraindication to MRI examination (people using a pacemaker or insulin pump, people with metal prostheses or intracerebral clips, people with metal fragments in their eyes, as well as claustrophobic subjects). A comprehensive list of contraindications is provided in Appendix 5. * Inability to perform the MRI without anaesthesia. * Refusal by the subject and/or those exercising parental authority/the subject's representative to be informed of any abnormalities detected during the MRI.