Final answer:
Self-recognition in humans typically emerges by about 18 months of age. As children grow, their self-concept becomes more sophisticated, moving from simple mirror self-recognition to understanding social roles and personal traits through childhood and adolescence.
Step-by-step explanation:
Research conducted by Lewis and Brooks-Gunn, as well as findings from other developmental psychologists, indicates that self-recognition typically emerges by about 18 months in human children. This milestone in self-awareness is often identified using the mirror test where a toddler recognizes that the reflection in the mirror with a red dot on their nose is actually themselves. Beyond simple recognition, as children grow towards 2 to 4 years old, they start to display a more sophisticated self-concept, recognizing themselves in pictures, developing social behaviors, and understanding gender roles and group memberships such as identifying with a grade level at school.
Following the progression through later stages of childhood, children gain the ability to understand personality traits and compare their abilities to their peers, contributing to the development of their self-esteem and sense of identity. The ability to form self-concept and reflect on self-traits continues to mature throughout childhood and into adolescence, solidifying the crucial cognitive and psychosocial development of recognizing one's self as a distinct individual.