In contrast one problem with Adorno's research is that it was only based on correlational data. This raises concern as the findings can only propose a relationship between personality and obedience rather than a causal relationship. Adorno et al. did find many significant correlations (e.g. authoritarianism and prejudice against minority groups) but no matter how strong the correlation, it cannot infer causation. The consequence of this is that neither Adorno or Milgram can claim that a harsh parenting style caused the development of an authoritarian personality, nor can it imply a causal connection between Authoritarianism and destructive obedience.