Wait, Where's the Flynn Effect on the WAIS-5?

Area of Science:

• Psychometrics
• Cognitive Psychology
• Developmental Psychology

Background:

• The Flynn effect (FE) describes a rise in IQ scores over time.
• This effect is incorporated into diagnostic criteria for intellectual disabilities and legal proceedings.
• The recent release of the Wechsler Adult Intelligence Scale, Fifth Edition (WAIS-5) prompts re-evaluation of the FE.

Purpose of the Study:

• To investigate whether the traditional Flynn effect persists into the 2020s.
• To analyze the magnitude of the FE using data from the WAIS-5.
• To assess the implications of FE changes for intellectual disability diagnosis and legal standards.

Main Methods:

• Two counterbalanced validity studies were conducted using the WAIS-5.
• Study 1: 186 adolescents and adults (16-90 years) tested on both WAIS-IV and WAIS-5.
• Study 2: 98 16-year-olds tested on WISC-V and WAIS-5.

Main Results:

• An unexpected reduction in the Flynn effect was observed.
• The FE decreased from an expected 3 IQ points per decade to 1.2 IQ points per decade.
• This reduction was noted across the validity studies.

Conclusions:

• The traditional Flynn effect appears to have diminished.
• The findings question the continued use of a 3-point adjustment for intellectual disability diagnoses.
• Reconsideration of federal court guidelines for capital punishment and high-stakes decisions is suggested.