On the other hand, there is evidence that challenges the link between LOC and resistance. For example, Twenge et al. (2004) analysed data from American LOC studies over a 40 year period. The data showed that over this time span, people have become more resistant, but also more external. This is surprising as if resistance was linked to an internal LOC, we would expect people to have become more internal. Therefore, this reduces the internal validity of LOC as it may not be an accurate explanation for why people are able to resist social influence.