FASD and Intellectual Disability Equivalence: A Meta-Analysis of Suggestibility During Forensic Interviews.

Area of Science:

• Neuroscience
• Psychology
• Forensic Science

Background:

• Intellectual Disability (ID) equivalence describes individuals functioning below ID criteria without meeting diagnostic thresholds.
• Fetal Alcohol Spectrum Disorder (FASD) often involves executive and adaptive deficits, overlapping with ID characteristics despite normal IQs.
• Interrogative suggestibility is a key forensic concern, particularly for vulnerable populations.

Purpose of the Study:

• To investigate shared vulnerabilities in interrogative suggestibility between FASD and ID.
• To be the first meta-analytic study comparing suggestibility in these two groups.
• To inform forensic interviewing practices for individuals with FASD and ID.

Main Methods:

• Two PRISMA-guided systematic literature searches across six databases.
• Inclusion of studies involving individuals with FASD or ID.
• Bayesian random-effects meta-analyses of Gudjonsson Suggestibility Scale-2 (GSS2) outcomes (Yield 1, Yield 2, Shift, Total Suggestibility).

Main Results:

• Individuals with FASD demonstrated interrogative suggestibility levels comparable to, and sometimes exceeding, those with ID across all GSS2 indices.
• Large effect sizes were observed for both groups.
• Individuals with FASD exhibited particularly elevated 'Shift' scores, indicating a higher tendency to alter responses after negative feedback.

Conclusions:

• FASD and ID share significant vulnerabilities in interrogative suggestibility.
• Both populations are highly susceptible to leading questions and interrogative pressure.
• Forensic interviewing requires careful consideration of FASD's heightened susceptibility to response modification.