Individuals with PWS are at risk of learning and attention difficulties. Curfs and Frym onducted research into the varying degrees of learning disability found in Prader Willi Syndrome (PWS). Their results were as follows:
* 5%: IQ above 85 (average to low average intelligence)
* 27%: IQ 70 – 85 (borderline intellectual functioning)
* 39%: IQ 50 – 70 (mild intellectual disability)
* 27%: IQ 35 – 50 (moderate intellectual disability)
* 1%: IQ 20 – 35 (severe intellectual disability)
* <1%: IQ <20 (profound intellectual disability)
Cassidy found that 40% of individuals with PWS have borderline/low average intelligence, a figure higher than that found in Curfs and Frym's study (32%). However, both studies suggest that most individuals (50–65%) fall within the mild/borderline/low average intelligence range.
Children with PWS show an unusual cognitive profile. They are often strong in visual organization and perception, including reading and vocabulary, but their spoken language (sometimes affected by hypernasality) is generally poorer than their comprehension. A marked skill in completing jigsaw puzzles has been noted, although this may be an effect of increased practise.
Auditory information processing and sequential processing are relatively poor, as are arithmetic and writing skills, visual and auditory short term memory and auditory attention span. These sometimes improve with age, but deficits in these areas remain throughout adulthood.