A2013 study (luby, et al) looked at three variables that mediate the impact poverty on hippocampus volume: parental education, parenting style and stressful life events. they found that parental education was not correlated with hippocampus volume. this finding was important because in this study, the variable, "parental education," served as a proxy for intelligence, an individual differences variable which is considered to have a genetic component. the lack of a relationship ruled out a rival hypothesis that the size of a child's hippocampus is