Final answer:
Socioeconomic status, social expectations, and cultural bias in IQ tests have been suggested as factors affecting children's IQ scores, which change due to a mix of environmental and intrinsic influences rather than being solely determined by genetics.
Step-by-step explanation:
The factors that contribute to the variability in children's IQ scores at different ages are numerous and complex. One such factor that has been suggested to contribute to changes in IQ scores is socioeconomic status. Children from impoverished backgrounds may experience daily stressors that negatively impact brain function and development, potentially leading to lower IQ scores. Moreover, different social expectations and educational opportunities based on gender or family encouragement can also influence the effort put into certain subjects, which can affect IQ scores. Cultural bias in IQ tests has also been acknowledged as a potential factor altering the accuracy of a child's IQ score. However, options like siblings' intelligence levels or genetic determinism as the sole factor influencing intelligence are not consistent with the broader understanding that multiple factors, such as environment, experiences, and education, fundamentally shape an individual's intelligence level.