Some researchers suggest that altruism operates on empathy. Empathy is the capacity to understand another person’s perspective, to feel what he or she feels. An empathetic person makes an emotional connection with others and feels compelled to help (Batson, 1991). Empathy can be expressed in several ways, including cognitive, affective, and motor. 

During adolescence, individuals experience significant cognitive development that enhances their understanding of others' emotions and thoughts, known as cognitive empathy. This period is marked by an increased ability to adapt to others' perspectives and a more nuanced understanding of others' mental states, a skill that is foundational for social problem-solving and conflict avoidance. The development of cognitive empathy relies heavily on the theory of mind — the...

The sense of smell is achieved through the activities of the olfactory system. It starts when an airborne odorant enters the nasal cavity and reaches olfactory epithelium (OE). The OE is protected by a thin layer of mucus, which also serves the purpose of dissolving more complex compounds into simpler chemical odorants. The size of the OE and the density of sensory neurons varies among species; in humans, the OE is only about 9-10 cm2.
The olfactory receptors are embedded in the cilia of the...