Final answer:
Lionel should become more aware of the Dunning-Kruger effect, which is the tendency for individuals with little expertise in a task to overestimate their own abilities. He should recognize that his perception of his expertise may be inaccurate and consider seeking further learning and experience in business.
Step-by-step explanation:
The cognitive bias that Lionel should become more aware of after taking two years of college economics courses is the Dunning-Kruger effect. This bias refers to the tendency for people with little expertise in a specific task to rate their knowledge higher than others who have more knowledge. It is a common illusion where incompetent individuals overestimate their own abilities.
In Lionel's case, he may think he knows enough about business to become a millionaire, but he should be cautious and recognize that his perception of his expertise may be inaccurate. It takes time and experience to truly build expertise in a subject area. By understanding the Dunning-Kruger effect, Lionel can better assess his knowledge and seek further learning and experience to truly succeed in business.