Final answer:
The main factor of personality development, according to psychoanalytical theory, is early childhood experiences, which are critical in shaping adult personality through a series of psychosexual stages proposed by Sigmund Freud. Erik Erikson later expanded this theory to encompass lifelong psychosocial development influenced by interactions with others.
Step-by-step explanation:
Psychoanalytical Theory and Personality Development
According to psychoanalytical theory, the main factor of personality development is the series of early childhood experiences that shape our personalities and behavior as adults. Sigmund Freud, the founder of psychoanalytical theory, proposed that personality develops through a series of psychosexual stages, which include oral, phallic, latency, and genital stages. Each stage is associated with a specific erogenous zone and developmental challenges. Successful navigation through these stages results in a healthy adult personality, whereas getting fixated at a stage due to improper resolution can lead to unhealthy personality traits. Freud emphasized that our personality is greatly influenced by our biological aggressive and pleasure-seeking drives, and how these drives are balanced with the internalized social controls (the superego).
However, psychologist Erik Erikson expanded on Freud's theory with his own psychosocial development theory. Erikson's theory suggested that personality development occurs throughout the entire lifespan and is affected by our interaction with others, leading to a development of ego identity through the negotiation between base desires and social acceptance.