Final answer:
Maslow's hierarchy of needs is doubted because it is based on subjective observations, doesn't consider cultural differences, and oversimplifies human motivation. Therefore, all of the given options contribute to the criticism of the theory.
Step-by-step explanation:
Researchers have doubted Abraham Maslow's hierarchy of needs for several key reasons. First, it has been suggested that Maslow's hierarchy is largely based on subjective observations rather than objective, empirical evidence. Second, the theory does not sufficiently account for cultural differences in needs, implying that what constitutes self-actualization, for example, may differ widely across cultures. Third, the complexity of human motivation is potentially oversimplified by Maslow's pyramid structure, which suggests a linear progression that does not account for the more dynamic aspects of motivation that can occur when multiple needs interplay at the same time. Therefore, the correct answer is that Maslow's hierarchy of needs has been doubted by some researchers for all the aforementioned reasons, 1) reliance on subjective observations 2) lack of accounting for cultural diversity, and 3) oversimplification of human motivation.