Fluid intelligence and executive functioning more alike than different?
OBJECTIVE
Fluid intelligence (Gf) has been related to executive functioning (EF) in previous studies, and it is also known to be correlated with crystallized intelligence (Gc). The present study includes representative measures of Gf, Gc, and EF frequently used in clinical practice to examine this Gf-EF relation. It is hypothesised that the Gf-EF relation is higher than the Gc-EF relation, and that working memory in particular (as a measure of EF) shows a high contribution to this relation.


METHODS
Confirmatory factor analysis was performed on a mixed neuropsychiatric and non-clinical sample consisting of 188 participants, using the Kaufman Adolescent and Adult Intelligence Test, and three executive tasks of the Cambridge Neuropsychological Test Automated Battery, covering working memory, planning skills, and set shifting.


RESULTS
The model fitted the data well [χ²(24)=35.25, p=0.07, RMSEA=0.050]. A very high correlation between Gf and EF was found (0.91), with working memory being the most profound indicator. A moderate to high correlation between Gc and EF was present. Current results are consistent with findings of a strong relation between Gf and working memory.


CONCLUSIONS
Gf and EF are highly correlated. Gf dysfunction in neuropsychiatric patients warrants further EF examination and vice versa. It is discussed that results confirm the need to distinguish between specific versus general fluid/executive functioning, the latter being more involved when task complexity and novelty increase. This distinction can provide a more refined differential diagnosis and improve neuropsychiatric treatment indication.
1Centre of Excellence for Neuropsychiatry,Vincent van Gogh Institute for Psychiatry,Venray,the Netherlands.
Loes
L
van Aken
2Donders Institute for Brain, Cognition and Behaviour,Radboud University,Nijmegen,the Netherlands.
Roy P C
RP
Kessels
1Centre of Excellence for Neuropsychiatry,Vincent van Gogh Institute for Psychiatry,Venray,the Netherlands.
Ellen
E
Wingbermühle
3Behavioural Science Institute,Radboud University,Nijmegen,the Netherlands.
William M
WM
van der Veld
1Centre of Excellence for Neuropsychiatry,Vincent van Gogh Institute for Psychiatry,Venray,the Netherlands.
Jos I M
JI
Egger
D000328:Adult; D003072:Cognition Disorders / Q000523:psychology; D003937:Diagnosis, Differential; D056344:Executive Function / Q000502:physiology*; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D007360:Intelligence / Q000145:classification* / Q000502:physiology; D007361:Intelligence Tests; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology; D008875:Middle Aged; D008960:Models, Psychological; D058027:Neuropsychiatry / Q000379:methods* / Q000706:statistics & numerical data; D009483:Neuropsychological Tests; D013647:Task Performance and Analysis
CANTAB; KAIT; confirmatory factor analysis; intelligence; neuropsychology