Joan Durrant at the University of Manitoba writes that a number of studies have found physical punishment to be associated with "higher levels of aggression against parents, siblings, peers and spouses", even when controlling for other factors. According to Elizabeth Gershoff at the University of Texas at Austin, the more that children are physically punished, the more likely they are as adults to act violently towards family members, including intimate partners. In countries where physical punishment of children is perceived as being more culturally accepted, it is less strongly associated with increased aggression; however, physical punishment has been found to predict some increase in child aggression regardless of culture. While these associations do not prove causality, a number of longitudinal studies suggest that the experience of physical punishment has a direct causal effect on later aggressive behaviors. In examining several longitudinal studies that investigated the path from disciplinary spanking to aggression in children from preschool age through adolescence, Gershoff concluded: "Spanking consistently predicted increases in children's aggression over time, regardless of how aggressive children were when the spanking occurred". similar results were found by Catherine Taylor at Tulane University in 2010. Family violence researcher Murray A. Straus argues, "There are many reasons this evidence has been ignored. One of the most important is the belief that spanking is more effective than nonviolent discipline and is, therefore, sometimes necessary, despite the risk of harmful side effects".