There are three grand theories providing theoretical framework for studying human development: psychoanalytic theory, behaviorism and cognitive theory.
The fundamental concepts of the psychoanalytic theory are the underlying forces (inner drives, mental and emotional processes, motives) shaping the personality, behavior, thinking, attitude, decision making, etc. Central to this theory, introduced by Sigmund Freud, is a point of view that a individual in his or her development passes through specific psychosexual stages: oral, anal, phallic, latent and genital. Ericson, who also contributed to the psychoanalytic theory, offered different classification of development stages. Each stage has its unique needs, motivation drivers, challenges and relationships. According to Freud, people act from three major states of the human being: the id, the ego and the superego; each of the states has its role and inner motives. The psychoanalytic theory emphasized the role of unconscious motivation and also of the early relationships between a child and the parents.
Behaviorism, in contrast to the psychoanalytic theory, analyses the human behavior – what people actually say and do, operating observable and measurable data and relying on experiments. Behaviorists are especially focused on specific guidelines or laws directing the actions (or responses to the environmental stimuli). Also, the behavioral theorists are interested in how people learn to behave in specific ways, distinguishing classical conditioning and instrumental conditioning. Accordng to behavioral theory, behavioral patterns can be modified through proper techniques (reinforcements or punishments.)
Cognitive theory puts cognition (processes of learning and knowing) as a key pillar. Cognition comprises the processes of percepting, accumulating, representing, organizing, retenting and transforming information in the processes of thinking, decision making, problem solving and directing the actions. Cognitive theory was originated by Jean Piagetm who broke down the cognitive development into four major age-related stages shaping specific manners of thinking, decision-making and behaving. According to cognitivists, cognitive equilibrium (or mental balance, consistency) is a key stimulus for people to acquire and assimilate new information and experience.
- Interaction between genes and the environment
Interaction between the genes and the environment was described for the first time in epigenetic theory of human development, contrasting with preformistic point of view, stating that genome predicts the development completely, and both personality traits and development path are inherited from the previous generations.
According to the epigenetic theory, the extent of manifestation of specific genetic predispositions is affected by the variety of physical and socio-cultural environmental fuctors such as climate and weather, nutrition composition, traumas, stress factors, occupation and major ativities, lifestyle, pattern of marriage and childbirth, life events, etc. The interaction between the genes and the environment goes with the mediation of behaviors and neural activity.
This interaction lasts for a lifetime for a specific individual. Genetics define a possible reaction range on external stimuli, but reactions within the range can vary a lot.
Some developmental aspects express more plasticity than others, some become more flexible with age, but even in adult age the environmental factors and context can interfere the inherited patterns.
So the genome acts in collaboration with epi- (external) factors. Genetics defines predispositions, variants, range of expression while environmental factors influence the direction and extent of manifestation of genetic predictors.
One specific feature is not governed by only one gene – it’s determined by a large number of genes in their combination; so, environmental factors can strengthen manifestations of one genetic predictors and inhibit the others in the described above combination.
- What genes are and how they influence human development
The human genome consists of genes, that are, respectively, composed of DNA codons. Genetics allows the inheritance of the specific traits from the previous generations. In general, genome is composed of the genes that are shared by all living creatures, of the genes attributable to humans only and of the genes that make an individual unique.
In interaction with the epigenetic factors affecting the expression of the genes, the genome sets the basis for human development through setting the basic physical and physiological framework for individual traits, development pattern, reactions, actions, etc.
For example, genome sets the basis for the blood type, hair and eye color, type of metabolism, body constitution, temperament, various personality traits, propensity to certain diseases and disorders, etc. Pace of basic stages of human development is also genetically predicted.
But, both physical phactors (for example, predispositions for illnesses or mental disorders) and behavioral factors are flexible and can be transformed in the process of personal development. For example, excercising can impact body shape or even height, diet and prevention measures can inhibit predisposition for a specific type of disease.
In the process of evolution, the human genome changes over time. In the process of selective adaptation, the particular traits are exhibited more or less frequently in humans over generations; those traits that contribute to survival and reproduction build up their presence in next generations, the others gradually disappear.
The direction of selective adaptations is defined by the direction of environmental changes, enabling adaptation of the human beings to new conditions of living and reproducing themselves.
- Erikson’s theory of childhood development
Erikson believed that human development lasts over the lifetime, focusing mostly on psychosocial development (in contrast with psychosexual stages introduced by Freud.) Erikson defined nine stages characterizing with the specific development task and challenges and conflicts for an individual to resolve.
These stages, in the childhood, are the following: trust vs. mistrust (aiming at developing trust to the World), autonomy vs. shame and doubt (with the ideal outcome of developing self-control and elaborating self-esteem), initiative vs. guilt when children learn directed and purposefull activity, industry vs. inferiority when people learn a sence of competency, identity vs. identity confusion (shaping the ego-identity).
Period of adolescence is marked with the following stages: intimacy vs. isolation (building relationship and carrer in an early adulthood), generativity vs. stagnation (embracing family and social relations), integrity vs. despair (with the preferred outcome of getting satisfacyion from the past experiences) and, finally, despair vs. hope and faith, aiming at reaching the wisdom.
Each stage contains an internal crisis, resulting in a polar discrepancy of the possible outcomes. Erikson emphasized the role of socio-cultural interactions. For early stages, for example, children receive and internalize responses from their family members (parents, grandparents, sisters and brothers), aligning internal motives and personal actions with social expectations.
Acording to Erikson, childhood, especially, first years of life are extremely important for further development. Unresolver earlier conflicts cause the sufficient problems, influencing the later stages. But, unlike Sigmund Freud, Erikson concentrated not only on pathological states and problems, but on achieving the desirable outcomes of every development stage and positive resolutions of the various identity crises the individual goes through during his life span.