English-speaking children exhibit difficulty in their comprehension of raising patterns, such as (1), in which the NP the boy is semantically linked to the VP in the embedded clause, but is syntactically realized as the subject of the matrix clause. (1) Raising pattern: [s "The boy" seems to the girl [s _ to be happy]]. This dissertation attributes this difficulty to an intervention effect stemming from the disruption of the association between the matrix and embedded subject positions by an overt intervening NP. A parallel effect has been widely discussed in relation to other patterns, in both adult and child language comprehension. A corpus study and a set of comprehension experiments reveal several key results. First, children very rarely hear or produce raising patterns with an experiencer. Second, children have difficulty comprehending raising sentences like (2) that contain an intervening experiencer, but this difficulty disappears when the experiencer is fronted to the beginning of the sentence, as in (3). (2) Donald seems to Mickey _ to be short. [Experiment 1] (3) To Mickey, Donald seems _ to be short. [Experiment 2] Third, children's comprehension also improves when there is an intervening pronominal experiencer as in (4), but no such effect is observed in the reverse situation, with a raised pronominal and a lexical NP experiencer, as in (5). (4) Donald seems to him _ to be short. [Experiment 3] (5) He seems to Mickey _ to be short. [Experiment 4] Finally, children have difficulty comprehending copy-raising patterns such as (6) when there is no gender cue available to help them correctly interpret the referent of the pronominal copy. (6) Donald seems to Mickey like he is short. [Experiment 5]. These results show that the difficulty associated with raising patterns cannot be attributed to children's grammatical deficits, as previously suggested (Borer & Wexler, 1987; Hyams & Snyder, 2005; Orfitelli, 2012; Wexler, 2004). Rather, it leads to a theory of Performance-based Intervention Effects (PIE) that attributes the difficulty to the disruption of the semantic link between the matrix and embedded subject positions by an overt intervening NP. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]