Some notes about various topics. ||| Gegenwärtig - vorübergehend -
wohl eher eine Gedankensammlung als ein Naturwissenschaftsblog. Das Konzept eines "Naturwissenschaftsblogs" wird erst im kommenden Jahr (2018/2019) Umsetzung finden.
Donnerstag, 21. Januar 2016
The secular decline in general intelligence from decreasing developmental stability: Theoretical and empirical considerations
Published data on secular trends in craniofacial fluctuating asymmetry are reanalyzed.
Significant linear increases in FA for white males and females are found spanning 160 years.
This suggests a secular decline in developmental stability.
FA and g are robustly negatively correlated.
Equivalent g-loss for the combined sex sample is −.16 points per decade.
The g-loss predicted based on genetic selection is smaller than that observed across various ratio-scale measures of cognitive ability. The difference may result in part from the accumulation of deleterious mutations across generations, reducing g via their effects on developmental stability/fitness. Previously published secular trend data on a developmental stability measure, craniofacial fluctuating asymmetry (FA) size, for white US males and females covering 14 and 15 decades respectively, are re-analysed. When the secular increases in FA size are rescaled as declines in latent developmental stability, and multiplied by the validity and reliability adjusted developmental stability-gcorrelation, g-losses of −.16 points per decade are predicted for the males, females and the combined sample. Predicted fitness losses due to mutation accumulation may account for 30% of the generational decline (−.05 points per decade), indicating only a small role for mutations in secular g-loss. The remaining 70% (−.11 points per decade) may result from developmental stability disrupting environmental change, such as increased exposure to pollutants. Adding these to the g-loss due to selection (re-estimated at −.54 points per decade) yields a combined decadal loss of −.70 points. Additional adjustments for replacement migration and the generation length-g interaction yield a larger magnitude decadal g-loss of − 1.25 points.