In this study the investigators will interrogate an existing data set to examine whether genetic variants contribute to an inverse association between weight status and cognitive function. Investigators hypothesize that body mass index (BMI) will be inversely related to a number of variables measuring cognitive function, and that that this inverse relation will be at least partially attributable to genetic variants which influence both BMI and cognition.

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:

• To examine the association between BMI and executive functioning (EF) in a sample of 869 twin children, ages 7 to 15 years old, who participated in the Texas Twin Project (TTP)
• To gauge the specificity of EF-BMI relations relative to academic achievement and general cognitive abilities.
• To examine the relative contribution of genetic and environment influences to the inverse association between BMI and EF

Inclusion Criteria:

All participants in the TTP database with executive functioning and BMI data, without a parent-reported medical disorder affecting growth

Exclusion Criteria:

Parent-reported medical disorder affecting growth More than one sibling in the dataset (if triplets are present, only two randomly selecting siblings will be included).

Individuals from the Texas twin Project dataset, who were twins and higher-order multiples previously recruited from the Houston and Austin Metropolitan areas, via flyers, the internet (study website) and contact through public school rosters

This protocol involves secondary data analysis of existing studies. Data will not be shared with other investigators since they should obtain data from the primary sources.