Intelligence Quotient (IQ)

Researchers have found that on average people with FASD generally have intelligence levels in the borderline to low average range, as measured on IQ tests. This means that they tend to have somewhat lower intellectual abilities overall. These lower IQ scores show up at a very young age and generally continue throughout a person's lifespan. However, this average is not necessarily representative of individuals with FASD as there is a large range of IQ scores in this population, from very high (above average) to very low (intellectual disability). Moreover, many researchers report that intellectual abilities in individuals with FASD are often unevenly developed, meaning that their full scale IQ score may not be the best indicator of how an individual may function.

For instance, IQ can be divided into a verbal domain and a visual domain. Individuals with FASD often have much higher scores in one domain over another. They might be much better at doing verbal tasks than visual/non-verbal tasks or vice versa. However, the number of people who have a better verbal IQ is about the same as the number of people who have a better visual IQ.

How do we know whether the difficulties experienced by people with FASD are due to fetal alcohol exposure or a generally lower IQ?

Researchers have compared individuals with FASD to individuals with no prenatal alcohol exposure, but similar IQ scores. A number of similarities and differences have been found:

  • Similar ability to switch mental concepts and strategies when requirements are changed
  • Similar ability to quickly give verbal responses
  • Similar fine motor skills
  • Similar ability to keep their attention focused on something
  • Similar language skills (i.e. understanding and expressing language)
  • Some similarities in tasks combining visual and spatial abilities
  • Similar ability to remember verbal information, although some deficits in verbal learning and memory are worse for children with FASD.
  • Children with FASD have more difficulty quickly giving non-verbal responses.
  • Children with FASD have more problems with social behaviours and thoughts, attention, delinquency, and aggression (adaptive behaviour and externalizing behaviour)

Although many people with FASD have an IQ within the “normal” range, they often are not able to function within the “normal” range for their age. That is, they may have average IQ, but below average adaptive function. With IQ often playing a large part in school assessment, children who have an average IQ might not end up receiving or qualifying for the services that they need for their difficulties in other areas. IQ may also be an important factor when patients apply for services and financial assistance are submitted in adulthood.