Final answer:
Fixation is the concept from Freud's psychosexual development theory referring to an individual being 'stuck' in an earlier stage due to unresolved issues, leading to specific adult behaviors.
Step-by-step explanation:
When an individual persistently focuses on an earlier psychosexual stage of development and gets 'stuck' because certain issues are not resolved, this is known as fixation. The concept originates from Sigmund Freud's theories on development, which outlines that children pass through several stages: oral, phallic, latency, and genital. If the issues pertinent to a specific stage aren't adequately dealt with, adults may exhibit certain behaviors that reflect these unresolved conflicts. For example, someone with an oral fixation might engage in overeating or binge drinking, while an fixation could result in a personality that is excessively orderly or neat.