title: Testosterone and nonverbal intelligence in right-handed men with successful and unsuccessful educational levels.
abstract: The relationship between serum total testosterone (T) concentration and fluid intelligence (nonverbal, spatial) was studied in consistently right-handed men with successful (S) or unsuccessful educational levels (NS). Hand preference was assessed by the Edinburgh Handedness Inventory. Nonverbal intelligence was measured by Cattell's Culture Fair Intelligence Test. Serum T level was determined using chemiluminescence enzyme-immunoassay on hormone autoanalyzer. There was no significant difference between the mean T levels of the S subjects and NS subjects, although S-men tended to have higher T levels than NS-men. The mean IQ was found to be significantly higher in S-men than NS-men. In the total sample (S + NS men), the correlation between T to IQ was best described by a polynomial regression (3rd order), exhibiting an inverse U-shaped regression. In S-men, the relationship between T and IQ was best described by a polynomial regression equation of the 3rd order; however, the relationship was not U-shaped, but rather a positive correlation (low T: low IQ and high T high IQ). In NS-men, there was an inverse U-shaped correlation between T and IQ (low and very high T: low IQ and moderate T: high IQ). The present data suggest that (i) very low and very high serum T concentrations may be disadvantageous, (ii) moderate T levels may be advantageous for general fluid intelligence, and (iii) a prewired cerebral organization may be essential for the T effects on cognitive abilities.
authors.affiliation: Department of Physiology, Medical School, Celal Bayar University, Turkey.
authors.forename: N
authors.initials: N
authors.lastname: Kutlu
authors.forename: N
authors.initials: N
authors.lastname: Ekerbicer
authors.forename: Z
authors.initials: Z
authors.lastname: Ari
authors.forename: B S
authors.initials: BS
authors.lastname: Uyanik
authors.forename: T
authors.initials: T
authors.lastname: Zeren
authors.forename: U
authors.initials: U
authors.lastname: Tan
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D004522:Educational Status; D007839:Functional Laterality; D006801:Humans; D007360:Intelligence / Q000502:physiology*; D007361:Intelligence Tests; D008297:Male; D012016:Reference Values; D013028:Space Perception / Q000502:physiology; D013223:Statistics as Topic; D013739:Testosterone / Q000097:blood* / Q000502:physiology
chemical_list: D015415:Biomarkers; D013739:Testosterone