Final answer:
The idea that intelligence is a fixed quantity unchangeable throughout a lifetime is false. Intelligence is influenced by both genetics and environment and can change, especially with the fluid aspects of intelligence that deal with problem-solving and adapting to new situations.
Step-by-step explanation:
The statement that intelligence can best be thought of as a fixed quantity that does not change over the lifetime is false. Research has shown that various factors influence intelligence, and it is not solely determined by genetics. The interplay between genetics and the environment contributes to one's cognitive development, and environmental factors can indeed provide both stability and change in the manifestation of intelligence. Additionally, theories like Cattell's divide intelligence into crystallized intelligence and fluid intelligence, with fluid intelligence particularly reflecting the ability to tackle complex problems and adapt to new situations, which can improve throughout one's life, especially during childhood and adolescence.
Controversially, Arthur Jensen's research suggested differences in intelligence among ethnic groups, which faced significant criticism for racial bias. It's important to understand that intelligence is a complex trait affected by many factors, and is not a static measure throughout one's life due to the dynamic nature of both genetics and environmental influences, as well as the subsequent discovery of the Flynn effect, where generational increases in IQ scores are observed.