The Intriguing Role of Spanish Language Vocabulary Knowledge in Predicting English Reading Comprehension C. Patrick Proctor Harvard Graduate School of Education Diane August Center for Applied Linguistics Marı ´a S. Carlo University of Miami Catherine Snow Harvard Graduate School of Education This study explored a holistic model of English reading comprehension among a sample of 135 Spanish–English bilingual Latina and Latino 4th-grade students This model took into account Spanish language reading skills and language of initial literacy instruction. Controlling for language of instruc- tion, English decoding skill, and English oral language proficiency, the authors explored the effects of Spanish language alphabetic knowledge, fluency, vocabulary knowledge, and listening comprehension on English reading comprehension. Results revealed a significant main effect for Spanish vocabulary knowledge and an interaction between Spanish vocabulary and English fluency, such that faster English readers benefited more from Spanish vocabulary knowledge than their less fluent counterparts. This study demonstrates the existence of literary skills transfer from the 1st to the 2nd language, as well as limits on such transfer. Keywords: bilingualism, vocabulary, cross-linguistic transfer, Spanish language The English reading achievement of English language learners (ELLs) is of abiding interest to researchers and practitioners, with contentious debates addressing the role of native language literacy skills and the impact of language of initial literacy instruction (Crawford, 1991; Hakuta, Butler, & Witt, 2000; Porter, 2000; Rossell, 2003; Snow, 1992). The purpose of the current study was to investigate the roles of language of initial literacy instruction and of first language (L1) literacy skills on the English (L2) reading comprehension of a sample of Spanish–English bilingual fourth graders. All of the students possessed some degree of oral proficiency in Spanish, and many had developed Spanish as well as English literacy skills. We addressed two research questions. First, what is the effect of language of initial literacy instruction on the L1 and L2 decoding skills, oral language proficiency, and reading comprehension of the students? Second, controlling for language of initial literacy instruction, L2 decoding skills, and L2 oral language proficiency, do analogue L1 decoding skills and oral language proficiency predict L2 reading comprehension? This study is a continuation of previous work that focused exclusively on predicting L2 reading comprehension from L2 decoding and oral language skills with this same sample of students (see Proctor, Carlo, August, & Snow, 2005). The Elusive Nature of Bilingualism The study of language and cognition among bilingual individ- uals is decades old. However, while bilingualism as a cognitive phenomenon has been researched for quite some time, its nature is both theoretically and empirically elusive, eliciting as many ques- tions as answers. For example, Lambert and Tucker (1972) sug- gested that those who are bilingual are able to compare their languages, resulting in enhanced metalinguistic ability. Metalin- guistic skills and cognitive flexibility have since been studied in bilingual individuals with some results pointing to a bilingual advantage (Hakuta, 1987; Hakuta & Diaz, 1985; Lemmon & Goggin, 1989) and others finding no such benefit (Jarvis, Danks, & Merriman, 1995). Grosjean (1998) indicated that studies in other domains of bilingualism, such as linguistics, psycholinguistics, and the neurology of language, have yielded similarly inconclusive results. Li (2002) lamented the resultant dearth of cognitive models of bilingualism, noting that research in this field must contend with a wide variety of factors in addition to those more common in monolingual research. Variables such as the amount of time spent learning the L2, context for L2 learning, social status of the L1 and the L2, and typological relationships between the L1 and the L2 are crucial considerations for understanding cognitive processes among bilingual individuals and have no relevance to monolingual populations. While reading as a cognitive process is no less subject to these considerations, similarities between bilingual and monolingual populations have been noted. Bialystok, Majumder, and Martin (2003) investigated the phonological development of monolingual English, bilingual Chinese–English, and bilingual Spanish– C. Patrick Proctor and Catherine Snow, Graduate School of Education, Harvard University; Diane August, Center for Applied Linguistics, Wash- ington, DC; Marı ´a S. Carlo, School of Education Research, University of Miami. Support for the research reported here was funded by the National Institute for Child Health and Human Development (Grant P01 HD39530). We extend our appreciation to the students, parents, teachers, and admin- istrators at the three schools in which data were collected for this project. Correspondence concerning this article should be addressed to C. Patrick Proctor, Harvard Graduate School of Education, Appian Way, Cambridge, MA 02138. E-mail: proctoch@gse.harvard.edu Journal of Educational Psychology Copyright 2006 by the American Psychological Association 2006, Vol. 98, No. 1, 159 –169 0022-0663/06/$12.00 DOI: 10.1037/0022-0663.98.1.159 159