Final answer:
An 8-month-old child's temperament is largely influenced by biological factors, which are innate traits that shape behavior and interaction with the environment.
Step-by-step explanation:
The temperament of an 8-month-old child is most likely a function of biological factors. According to psychological research, temperament is an innate trait that manifests early in life and is influenced by genetic and biological factors. Thomas and Chess (1977) categorized temperaments into three types: easy, difficult, or slow to warm up. Babies are born with a predisposition towards a specific temperament, which shapes how they think, behave, and interact with their environment. However, it's important to acknowledge that environmental factors and maturation can interact with a child's inborn temperament, potentially influencing the expression of their personality.