Yawning is often "contagious". However, psychopaths this rule does not apply. They don't want to yawn, when next to them is yawning. This confirms a study involving 135 volunteers from among students, writes The Daily Mail.
The volunteers were asked to take a test to assess personality traits. Scientists considered traits such as the tendency to manipulate others to their advantage, rebellion, selfishness. Next, students were shown a video taped people's faces with different emotions. Some people with screen yawned.
Less responsive to the yawning callous people. Scientists believe that this reaction is tightly connected with a feeling of compassion or empathy. Sometimes on this basis we can assume the presence of one of the mental disorders.
Note, among wild animals yawning – the signal for bedtime. Leaders chimpanzees, baboons and dogs use it to monitor your group.