Tailored for scholars and researchers in linguistics, psycholinguistics, and cognitive science, this monograph embarks on an in-depth exploration of the intriguing realm of long-distance dependencies in human language. These dependencies exhibit a compelling duality: they are unbounded, as they extend across an arbitrary number of words, yet they are constrained by the grammar. Historically, linguists and psycholinguists have pursued distinct paths to account for the intricacies of these dependencies. Bridging these traditions together, this monograph leverages the concept of similarity, focusing on two canonical phenomena in theoretical linguistics and psycholinguistics: wh-islands and agreement attraction. These serve as test cases for an extensive empirical and theoretical investigation, unraveling the interplay between formal linguistic properties and memory operations.