How is the directionality problem different from the third variable problem? - Answers

The directionality problem refers to the ambiguity in determining the causal relationship between two variables—whether A causes B or B causes A. In contrast, the third variable problem arises when a third variable influences both A and B, creating a spurious correlation between them without indicating a direct causal relationship. While the directionality problem focuses on the sequence of effects, the third variable problem highlights the influence of an external factor that complicates the interpretation of the relationship between the two primary variables.