The article, titled "The Development of Empathy in Twins,"explores the way empathy manifests itself in the behaviors of twins. One observation speaks to the signals of empathy at a young age and how they evolve with age:
"...reflexive or contagious crying of infants is viewed as a precursor of affective arousal that reflects concern for the other. Self-distress diminishes over time and is gradually replaced by more modulated expressions of concern. Young children’s emotional states become less tightly fused with those of others as they come to recognize their existence as separate, autonomous beings."
I found it curious, the correlation between age and mental compartmentalization with regard to empathy development. Perhaps, this idea explains the jaded feeling that often settles in with old age.