A meta-analytic review of the MMPI validity scales and indexes to detect defensiveness in custody evaluations

Abstract

Background/Objective: In child custody disputes, one of the remit of the forensic psychologist is to evaluate parental attributes while suspecting defensiveness. The instrument of choice for undertaking this double task is the MMPI. Method: As to establish the state of the art on this, a meta-analysis was undertaken with a total of 32 primary studies from which 256 effect sizes were assessed. A meta-analysis was undertaken, effect sizes were corrected for sampling error and criterion unreliability. Results: The results revealed a positive, significant, large and generalizable mean true effect size for the L, K, S and MP scales, and the L+K and L+K-F indexes. The Wsd was positive, significant and large, but not generalizable. A negative and significant, but not generalizable mean true effect size was found for the F and generalizable for F–K index. The effect sizes for the L, K, S and MP scales, and the L+K and L+K-F indexes were equal. Both the gender of parents (father vs. mother) and the context of evaluation (parent child custody disputes vs. parenting capacity) were assessed as moderators. Conclusions: The results are discussed in relation to forensic practice.