DEFINITION AND NATURE OF DEVELOPMENTAL PSYCHOLOGY Developmental Psychology is one of the sub-fields of Psychology. It is an ontogenetic study of human organism from conception to death. Developmental Psychology seeks understanding and controls the basic processes and dynamics underlying human behavior at the various stages of life. Its investigations encompass the growth and maturation of the individual organism, its cognitive and emotional powers, as well as its personality structure. Developmental Psychology, as a science of growth, deals with all the processes contributing to becoming an infant, a child, an adolescent, and a mature adult. According to Hurlock, "Developmental Psychology is the branch of psychology that studies intraindividual changes and interindividual changes within these intraindividual changes. Its task is not only description but also explication of age-related changes in behaviour in terms of antecedent consequent relationship." Some developmental psychologists study developmental changes covering the life span from conception to death. Others cover only a segment of the life span, childhood or old age. Developmental Psychology is a scientific discipline that attempts: (I) to devise methods for studying organisms as they evolve over time ( U ) to collect facts about individuals of different ages, backgrounds and personalities and (iii) to construct a theoretical frame work that can account for the observed behaviors as well as for the changes occurring throughout the life cycle. ASPECTS OF DEVELOPMENT There are four aspects of development which are closely intertwined. Each aspect of development affects the other 1. Physical development 2. Intellectual development 3. Personality development 4. Social development We will now discuss each of these in brief. 1. Physical development. Physical development consists of changes in the body, brain, sensory capacities and motor skills. They exert major influences on both intellect and personality. For example, much of an infant's knowledge comes from the senses and from motor activity. A child who has a hearing loss is at risk of delayed language development. In late adulthood, physical changes in the brain as in Alzheimer's disease - which has been estimated to affect about 10 percent of people over the age of 65 (Evans et aL 1989) can result in intellectual and personality deterioration. 2. Intellectual development, Changes in mental abilities - such as learning, memory, reasoning, thinking and language are aspects of intellectual development. These changes are closely related to both motor and emotional development. A baby's growing memory, for example, is related to separation anxiety, the fear that the mother will not return once she has gone away. If children could not remember the past and anticipate the future, they could not worry about the mother's absence. Memory also affects babies’ physical actions. For example, a one-year old boy who remembers being scolded for knocking down his sister's block tower may refrain from doing it again. 3. And 4 personally and Social development. Personality and social development affect with the cognitive aspects and the physical aspects of functioning. For example, anxiety about taking a test can impair performance; and social support from friends helps people cope with the negative effects of stress on their physical and mental health. PRINCIPLES OF DEVELOPMENT Development follows certain principles. These principles are: (i) Development is similar for all: All children follow a similar pattern of development, with one stage leading to next. For instance, they baby stands before he walks, or draws a circle before a square. (ii) Development Proceeds at Different Rates: Even though all individuals follow much the same pattern of development, the rate of development varies form individual to individual. Because rate of development differ, all children of the same age to do not reach the same point of physical or mental development. Nor do all individuals decline physically or mentally at the same rate. In the same individual, different physical and mental traits develop at different ages. Different rates of decline have likewise been observed for different physical and mental traits. (iii) Development is continuous: From the moment of conception to the time of death, changes re taking place within the individual, sometimes slowly. As a result, what happens at one stage of development varies over and influences the following stages. Unhealthy attitudes developed in childhood, for example, have been found to be at the root of much of the unhappiness and poor adjustment during middle and old age. (iv) Development Proceeds from General to Specific Responses: In mental as well as motor responses, general activity always precedes specific activity. For example, the baby waves his arms in general movements before he is capable of a specific a response as reaching. Studies of speech have revealed that the young child learns general words before he learns to call each toy by its name. (v) All Individuals are Different: Although all individuals follow a definite and predictable pattern of development each individual has his own distinct style of doing so. Some develop in a smooth, gradual, step by-step fashion, while others move in spurts. Some show wide swings, while others show only slight ones. Individual differences are due partly to differences in hereditary endowment and partly to environmental influences. There are fewer differences in physical structure than in intellectual differences. Difference in special aptitudes seems to be the most mark of all. (vi) Direction of Physical Development: Physical development follows two laws: (a) Cephalocaudal Principle. This means that improvements in structure as well as in control of different areas of the body come first in the head region, then in the trunk, and last, in the leg region. No only do the structures in the head region develop sooner than those in the leg region, but not or control comes first in the upper areas of the body and last in the lower areas. (b) Proximodistal Principle. According to this principle, development proceeds from near to far-outward, from the central axis of the body toward the extremities. Head and trunk develop before the limbs. Arms develop before the fingers. Functionally, the baby can move his hands as unit before he can control the movement of his fingers. (vii) Each Stage has characteristic Traits. Our life span is divided into a number of stages, namely, parental stage, infancy, childhood, adolescence, adulthood and old age. Each of these stages is characterized by certain problems of adjustment. (viii) Development comes from Maturation and learning. Physical traits are developed in two ways, partly from intrinsic maturing of these traits and partly from exercise and experience of the individual. Development through intrinsic maturity is known as Maturation and development through one's experience and exercise is termed Learning. (ix)Development follows a Familiar and Predictable Pattern. There is a particular pattern of development for each species, animal or human. Development follows a regular genetic sequence during the prenatal period, in progressive stages. Similarly, the postnatal period also witnesses an organized development, although facts develop more quickly than memory for abstract or theoretical thinking. Cases of incompatibility in the rate of development of different physical and mental traits, lead to problems in adjustment. If the intellectual development exceeds or outpaces the physical, emotional or social development the child will be out of step, with his contemporaries or even other children. (x) The global of all development is self-realization: In general, the overall goal or objective of individual development is self-realization which is defined as the motive to achieve one's potential. It is difficult to define what maturity is. A person who has attained physical maturity may still want in intellectual maturity with a still longer way to go to reach social or emotional maturity. Further, the level of maturity for one person may not be applicable to the other. Each person is endowed with certain growth potentials which can be developed to maximum level for that individual, given a favorable environment.