Empathy is a reflex emotion that has to be learned at a young age. Not all humans have empathy: the lacking of all forms of empathy is called psychopathy (see also antisocial personality disorder). Autism and Asperger's disorder are often falsely associated with empathy disorders, due to developmental differences in the ways emotions are experienced and expressed.
The empathy reflex is exploited to a certain extent in all kinds of fiction, thus we may identify deeply with characters appearing in a text or on a screen. It is also possible to identify with a person of the other sex or an animal. Empathy is thought to be a driving psychological force behind the animal rights movement.
Some students of animal behaviour claim that empathy is not restricted to humans as the definition implies. Examples include dolphins saving humans from drowning or from shark attacks, and a multitude of behaviours observed in primates, both in captivity and in the wild. See, for instance, the popular book
In science fiction, empathy (and the cooresponding noun empath) is used to signify a paranormal ability to sense the emotions of others, as opposed to telepathy, which allows one to perceive thoughts as well.