altruism does exist and is evoked by the empathic desire to help someone who is suffering. Feelings of empathic concern are contrasted with feelings of personal distress, which compel people to reduce their own unpleasant emotions and increase their own positive ones through helping someone in need. Empathy is thus not selfless, since altruism works either as the way to avoid those negative, unpleasant feelings and have positive, pleasant feelings triggered by others' need for help, or as the way to incentive the gain of social reward or through fear to avoid social punishment by helping. People with empathic concern help others in distress even when exposure to the situation could be easily avoided, whereas those lacking in empathic concern avoid helping unless it is difficult or impossible to avoid exposure to another's suffering. Helping behavior is seen in humans at about two years old, when a toddler is capable of understanding subtle emotional cues. In psychological research on altruism, studies often observe altruism as demonstrated through prosocial behaviors such as helping, comforting, sharing, cooperation, philanthropy, and community service. Research has found that people are most likely to help if they recognize that a person is in need and feel personal responsibility for reducing the person's distress. Research also suggests that the number of bystanders witnessing distress or suffering affects the likelihood of helping (the Bystander effect). Greater numbers of bystanders decrease individual feelings of responsibility. However, a witness with a high level of empathic concern is likely to assume personal responsibility entirely regardless of the number of bystanders. Many studies have observed the effects of volunteerism (as a form of altruism) on happiness and health and have consistently found a strong connection between volunteerism and current and future health and well-being. In a study of older adults, those who volunteered were higher on life satisfaction and will to live, and lower in depression, anxiety, and somatization. Volunteerism and helping behavior have not only been shown to improve mental health, but physical health and longevity as well, attributable to the activity and social integration it encourages. One study examined the physical health of mothers who volunteered over a 30-year period and found that 52% of those who did not belong to a volunteer organization experienced a major illness while only 36% of those who did volunteer experienced one. A study on adults ages 55+ found that during the four-year study