Island effects are one of the most studied phenomena in experimental syntax. There are at least two reasons for this. First, they are a terrific case study for a number of foundational questions in linguistics, covering topics such as the complexity of the grammar, the variation of languages, the dynamics of sentences processing, and the acquisition of abstract constraints. Second, they are a valuable case study for illustrating the benefits of formal experiments, such as defining an effect, isolating the source of an effect, and increasing the precision of the empirical bases of linguistic theories. In this chapter, we illustrate these benefits of formal experiments for island effects by reviewing the major empirical contributions that formal experiments have made to theories of island effects over the past two decades. Along the way, we also provide a relatively comprehensive list of articles that have used formal experiments to explore island effects.

In research on heritage speakers, it is often observed that areas of core syntax tend to be resilient and resemble the relevant baseline. This chapter discusses this generalization and provides examples of areas that tend to be resilient and areas that are vulnerable. Research into the syntax of heritage speakers has tended to focus on certain areas, such as argument structure and the representation of null arguments, meaning that a lot of grammatical domains have not been sufficiently explored. This chapter nevertheless tries to summarize the main findings and outline important methodological and theoretical issues that any work on heritage syntax needs to consider carefully. Examples of the latter include the question of what the appropriate baseline for comparison is, and how to adequately separate morphology and syntax. Empirically, the chapter will consider lexical categories, passives, and verb second as examples of relatively resilient areas of syntactic representations. In terms of areas that are more vulnerable, it will look at word order, long-distance dependencies, and discontinuous dependencies.