IQ more variable than previously thought

It has generally been thought that IQ is fairly stable from the teen years onwards. Non-cognitive ability however has been seen as more malleable & this idea has featured in Jim Heckman's work especially since non-cognitive ability seems to be quite important for labour market outcomes. However based on this study it now seems that IQ varies much more than previously thought for teenagers. What is not clear is whether it can be actively increased by interventions.