Development is the act or process of growing or causing something to grow or to become larger or more advanced. The life span perspective of development involves understanding changes that occur in every period of development. This view seeks to understand people throughout the changes in life and how these changes shape an individual into whom they become. All these changes occur from birth, throughout a persons’ life, into and during old age. Life span development is multidirectional, multi contextual, multicultural, multidisciplinary and plastic. It is multi-directional because it can go in different directions instead of following just one path. Because of the different contexts, events and situations it is multi contextual and can be further broken down into the historical context and the socioeconomic context. Being multicultural it accepts information and behaviors shared within a certain group. Culture is frequently interchanged with ethnicity and race. It is multidisciplinary because it welcomes the input from different aspects or fields of psychology or science. Lastly development is plastic because it continually evolves and changes. It can be molded into different shapes and forms.

A theory is as an idea or a set of ideas that are intended to explain facts or events. The beginning of the twentieth century saw the birth of two new theories. The psychoanalytic theory and behaviorism became the two general theories of psychology. Originating from Sigmund Freud, the psychoanalytic theory contends that the root of human behavior starts with unconscious thoughts and internal debates. The first six years of life are divided into three stages of development - the oral stage, the anal stage, and the phallic stage. Freud further stated that two more developmental periods follow in early childhood. There is latency and the genital stage. Freud characterized each stage with a sexual nature. He did not believe that there were any new stages occured during adulthood. Erik Erikson view on human development consisted of eight different stages. Trust versus mistrust, autonomy versus sham and doubt, initiative versus guilt, industry versus inferiority, identity versus role confusion, intimacy versus isolation, generativity versus stagnation, integrity versus despair. Each stage is characterized with what he considered a developmental crisis. Where Freud related developmental stages with sexual urges Erikson viewed it as relationships with people.

Behaviorism, also called the learning theory, focused on behavior that could be observed and measured. Behaviorsists believe that responses to environmental stimuli shape our behavior. It stipulates that regardless of an individuals genetics or individual traits a person can be trained or conditioned to behave in a particular way. Conditioning is broken down into two spectrums. Classical conditioning and Operant conditioning. Classical conditioning is when an individual is conditioned to pair a neutral stimulus with response. After a period of time the neutral stimulus is will be eventually paired with a naturally occurring stimulus. Operant conditioning, also known as instrumental conditioning, is the method wherein learning is done with reward or punishment. If the resulting behavior elicits joy or pleasure then an individual will be more apt to repeat that specific behavior. If the resulting behavior causes discomfort or displeasure then that specific will be avoided or less likely to recur. Social learning, also called observational learning, can occur purely from observation or direct instruction. This type of learning may be achieved through modeling. Modeling should not be mistaken with mimicking. Individuals may model some actions but not all. Whereas mimicking involved mirroring the observed behavior without veering away from any observed behavior.

Heredity and the environment or nature versus nurture is an age old debate in which one argues if development is inherently from within or can be changed by environment. Heredity is is the transmission of genetic characteristics from parents to offspring. It is the sum total of inherited factors or characteristics. Environment is the aggregate of surrounding things, conditions, or influences. It is the social and cultural forces that shape the life of a person. Heredity deals with genetics, the individuals DNA. A persons hair color, eye color, skin tone is all inherited from the biological parents. Diseases may also be inherited from the parents. Some examples are cystic fibrosis, diabetes, sickle cell anemia. The environment deals with influences such as living conditions, emotional attachments, even climate. Both factor in on how an individual is shaped and also influence one another. An example would be siblings who are separated. They may share the same hair color and even a disease like diabetes for example. One may grow up in an environment where there are people around that are more educated and in turn take a more pro-active role in controlling this disease like encouraging physical activity and right diet choices. On the other hand the other sibling may grow up in a household with other individuals that may not be concerned with proper diet to exercise which in turn makes the disease harder to manage.