Investigators will use existing data collected as part of the Texas Twin Project (TTP). TTP collected neuropsychological task data on cognition (executive functioning and general cognitive abilities) from a computerized test battery, as well as BMI data, on a sample of 869 twins. Investigators will use information from the known extent of genetic and environmental sharing between members of MZ (monozygotic; identical) and DZ (dizygotic; fraternal) twin pairs to quantify the genetic correlation between measures of cognition and BMI using biometric genetic modeling under the assumptions of the classical twin model. The specific aims are: