Final answer:
Adam Smith criticized substantivists' lack of attention to individual action and behavior and focused on scientific investigation into individual economic behavior and rationality.
Step-by-step explanation:
The person who criticized substantivists' lack of attention to individual action and behavior and focused on scientific investigation into individual economic behavior and rationality is Adam Smith. Smith, the father of modern economics, emphasized the role of self-interest and altruism in individual economic behavior. In his book, The Theory of Moral Sentiments, Smith argued that individuals are both self-interested and concerned about the well-being of others.