The areas of the tongue sensitive to tastes. The classical theory about the physiology of taste recognizes the existence of four fundamental tastes - sweet, salty, sour and bitter - each being perceived by specific areas of the tongue by means of gustatory receptors, also known as taste buds.
Theories of Aging. Theories of Aging. Erik Erikson, who took a special interest in this final stage of life, concluded that the primary psychosocial task of late adulthood (65 and beyond) is to maintain ego integrity (holding on to one's sense of wholeness), while avoiding despair (fearing there is too little time to begin a new life course).
The study of aging - gerontology - is a relatively new science that has made incredible progress over the last 30 years. In the past, scientists looked for a single theory that explained aging. There are two main groups of aging theories. The first group states that aging is natural and programmed into the body, while the second group of aging theories says that aging is a result of damage which is accumulated over time. In the end, aging is a complex interaction of genetics, chemistry, physiology, and behavior. Theories of Aging. By understanding and describing how we age, researchers have developed several different theories of aging. The two categories are programmed theories and error theories. 1  Programmed Theories assert that the human body is designed to age and there is a certain biological timeline that our bodies follow. 2  Error Theories assert that aging is caused by environmental damage to our body's systems, which accumulates over time.