Killer whales display personality traits similar to those of humans and chimpanzees, such as playfulness, cheerfulness and affection, according to new research.
"This is the first study to examine the personality traits of killer whales and how they relate to us and other primates," said lead researcher Yulán Úbeda, a doctoral student in psychology at the University of Girona in Spain. "These similar personality traits may have developed because they were necessary to form complex social interactions in tightly knit groups that we see in killer whales, humans and other primates."
Look at how humans treat other humans who have any condition, mental or physical, that impairs playfulness, cheerfulness, or affection.
Yeah. "Required" is right. You're pretty much not allowed in society if you can't perform those functions on demand. :/