Although the debate continues regarding which has the greater effect on human behavior, it is generally accepted that the contributing factors of both nature (innate traits) and nurture (acquired traits) account for the wide variety of personalities, career paths and emotional characteristics among individuals in a society. The mid-20th century saw a shift away from the role played by genetics, or the "nature" factor, in personality development as researchers began to lean more towards the role played by an individual's interaction with their environment, or the "nurture" factor. By the latter part of the 20th century, the more influential focus was no longer centered around behavior developing independently of environment and viewed instead as an interactive process involving inherited traits, upbringing, peer experiences, random environmental events, media and socioeconomic status.
Research appears to show that a trait such as an individual's IQ level, commonly assumed to be an inherited trait, can be subject to alteration by the influence of family environmental factors. Culture is also a factor in the development of behavioral traits because of its generation-to-generation transmission of accepted social norms and parameters.
The 20th-century developmental psychologist, Erik Erikson, proposed that individuals develop their personalities, learning abilities and social skills by progressing through a series of eight interactive stages beginning in early childhood and ending in the years between 50 and 70. At each stage, the developing individual encounters various types of environmental crises, and by successfully overcoming each specific crisis, moves on the next stage in the developmental sequence.