NEWS | August 15, 2018

UC Davis MIND Institute researchers method to improve IQ test sensitivity now widely available


UC Davis MIND Institute researchers from the Translational Psychophysiology and Assessment Laboratory (T-PAL) developed a method to improve IQ test sensitivity and remove barriers associated with floor effects in people with intellectual disabilities. The scoring eliminates floor effects, which occur when a large portion of examinees score at or near the measure’s lower limit for potential responses.

David Hessl David Hessl

PRO-ED, Inc., publisher of one of the most widely used IQ tests, the Stanford-Binet Intelligence Scales, has adopted the scoring approach, which makes it possible for clinical psychologists, school psychologists and others who work with people with intellectual disabilities to use the method in their clinics and schools.

“Floor effects are really pervasive when testing people with intellectual disabilities with standardized tests like IQ tests,” said David Hessl, UC Davis professor in the Department of Psychiatry and Behavioral Sciences and T-PAL director. “This makes it impossible to know a person’s true level of abilities, and the flooring really hides their true strengths and weaknesses.”

The alternative approach was integrated into the web-based version of the Stanford-Binet, which is commonly used to evaluate the level of global intellectual functioning among individuals with neurodevelopmental disorders. This scoring method is more useful when an examinee receives multiple floored scores, or scores that are below what is measurable.

“This method basically uncovers the true variation in cognitive abilities and allows us to measure IQ more accurately in the low end and detect IQs below the usual floor,” said Hessl. “We worked hard with PRO-ED, Inc. over the past few years to make this possible, and we are very excited that it is reaching the broader research, special education and clinical communities.”

Hessl and T-PAL colleagues are currently conducting additional studies of this new method. For example, researchers are examining how the alternative scoring approach versus the traditional method might influence clinicians and special educators to guide treatment and individualized education plans.

“We are really interested in learning whether this new method and more sensitive scores will change the ways professionals view their patients/students and if it changes their treatment and curriculum planning,” Hessl said.