The presence of a crossover effect in one's data can usually rule out the influence of which rival hypothesis?

The presence of a crossover effect in one's data can usually rule out the influence of Regression Artifact hypothesis.

Explanation:

When you collect any non-random samples from a group of people, and when those collected samples imperfectly match those samples that's when the Regression artifact occurs.

To put it in simple words, its actually a hypothesis to get to know the relationship between the two types of variables (dependent and independent ones). Many studies were conducted to perform this hypothesis, and the results obtained were based of the figurative study. Regression artifact also have a pseudo effect in some cases.