A study by El-Sheikh et al. (2010) found that compared to white children, black children from both low- and middle-income families __________.
◦ had lower levels of aggression if they slept poorly
◦ had higher levels of aggression if they slept well
◦ did not differ in aggression levels from white children if they slept well
◦ had the same levels of aggression regardless of whether they slept well or not