Intervention effects refer to the inability of an in-situ wh-phrase to be preceded by certain quantificational elements. The characterization of which quantifiers are interveners, and the nature of intervention itself, has been subject to great debate. We show that the following holds in Japanese: The intervention/scope-rigidity generalization: Scope-rigid quantifiers above an insitu wh cause intervention. Quantifiers that allow scope ambiguities - i.e., those that allow reconstruction - do not. This correlation is explained by a widely-discussed incompatibility between predicate abstraction (for quantifier scope-taking) and the computation of Rooth-Hamblin alternatives (for wh-in-situ).