Heritability of metacognitive judgement of intelligence: A twin study on the Dunning-Kruger effect

Metacognition is a process that relates to thinking about thinking. Observed variation in metacognitive processes related to intelligence have often been referred to as the Dunning-Kruger effect (DKE). The DKE describes how individuals often overestimate their competence in a field where they lack expertise, while experts tend to slightly underestimate their competence. Applied to general intelligence, the DKE suggests discrepancies between self-assessed intelligence (SAI) and objective measures of intelligence. Recently, however, the methods used to assess the DKE have been subject to critique. The current study innovatively assessed the DKE by using a mechanistic and genetically informed approach. ACE decomposition models were estimated on a large sample of twins (n = 920; [nMZ = 388; nDZ = 532]) drawn from the restricted version of the National Longitudinal Study of Adolescent to Adult Health. Findings illustrated that about 44 % of the variance in a traditional measure of the DKE (difference scores: SAI – objective IQ) was accounted for by genetic factors in the full sample. However, the pattern differed over quartiles of objective IQ where genetic factors accounted for less of the variance in the lower quartiles (about 30 %) and increased to over 75 % of the variance in the highest quartile (remaining variance was due to nonshared environmental factors). Limitations notwithstanding (including a weak and relatively isolated DKE), the current study adds potential support for the validity of the DKE.