Abstract
As systematic research syntheses and meta-analytic studies are becoming more prominent in the social sciences, especially in the fields of psychology and ed-ucation, it appears that applied linguists have also started to follow suit (In’nami et al., 2019). One of the main reasons for this is that abundant knowledge has accumulated through the years about second and foreign lan-guage (L2) learning and teaching, making the time ripe to systematically syn-thesize the research findings in order to draw further conclusions and identify paths future studies could take. This is also true for the subfield of individual differences (IDs) research within applied linguistics, where proliferation in the number of studies focusing on individual learner differences with respect to a large variety of issues has been witnessed in the past decades. Hence, we saw it timely to compile a special issue on research synthesis in the subfield of IDs in L2 learning. We formulated the following aims to guide our venture: First of all, we intend to inform scholars of the nature and utility of research syntheses in our field. Second, we hope that the articles included in the special issue would serve as examples for researchers wishing to embark on conducting similar studies. Our third and not negligible aim was to see what tendencies regarding particular individual differences can be outlined based on previous research results. In order for the readers to make the most of these articles, in this editorial introduction we would like to articulate how we see the role of research synthesis in general and meta-analysis in particular in our field. To this end, we will offer relevant definitions and a short discussion on their utility. We will then move on to outline very generic guidelines for conducting sys-tematic research syntheses, and, finally, we will summarize the studies includ-ed in the volume and their contribution to the field of research on IDs.
References
Al-Hoorie, A. H. (2018). The L2 motivational self system: A meta-analysis. Studies in Second Language Learning and Teaching, 8, 721-754. https://doi.org/10.14746/ssllt.2018.8.4.2
Boo, Z., Dörnyei, Z., & Ryan, S. (2015). L2 motivation research 2005-2014: Under-standing a publication surge and a changing landscape. System, 55, 145-157.
Borenstein, M., Hedges L. V., Higgins, J. P. T., & Rothstein, H. R. (2005). Comprehensive meta-analysis (version 2.2.027) [computer software].
Botes, E., Dewaele, J.-M., & Greiff, S. (2020). The Foreign Language Classroom Anxie-ty Scale and academic achievement: An overview of the prevailing literature and a meta-analysis. Journal for the Psychology of Language Learning, 2, 26-56.
Card, N. A. (2012). Applied meta-analysis for social science research. The Guilford Press.
Cho, K. (2015). Meta-analysis of factor analyses: Comparison of univariate and multivariate approaches using correlation matrices and factor loadings [Unpublished doctoral dissertation]. The Florida State University.
Chong, S. W., & Plonsky, L. (2021a). A primer on qualitative research synthesis in TESOL. TESOL Quarterly, 55(3), 1024-1034.
Chong, S. W., & Plonsky, L. (2021b, June 15). A typology of secondary research in applied linguistics. https://doi.org/10.31219/osfi.o/msjrh
Donker, A. S., de Boer, H., & Kostons, D. (2014). Effectiveness of learning strategy instruction on academic performance: A meta-analysis. Educational Research Review, 11, 1-26.
Dörnyei, Z. (2007). Research methods in applied linguistics: Quantitative, qualitative and mixed methodologies. Oxford University Press.
Duval, S., & Tweedie, R. (2000). Trim and fill: A simple funnel-plot-based method of testing and adjusting for publication bias in meta-analysis. Biometrics, 56, 455-463. https://doi.org/10.1111/j.0006-341x.2000.00455.x
Elahi Shirvan, M., Khajavy, G. H., MacIntyre, P. D., & Taherian, T. (2019). A meta-analysis of L2 willingness to communicate and its three high-evidence correlates. Journal of Psycholinguistic Research, 48, 1241-1267. https://doi.org/ 10.1007/s10936-019-09656-9
Granena, G., & Yilmaz, Y. (2019). Language aptitude profiles and the effectiveness of implicit and explicit corrective feedback. In R. P. Leow (Ed.), The Routledge handbook of second language research in classroom learning (pp. 440-453). Taylor & Francis.
Gurzynski-Weiss, L., & Plonsky, L. (2017). Look who’s interacting: A scoping review of research involving non-teacher/non-peer interlocutors. In L. Gurzynski-Weiss (Ed.), Expanding individual difference research in the in-teraction approach: Investigating learners, instructors, and other interlocutors (pp. 305-324). John Benjamins.
Henry, A., Sundqvist, P., & Thorsen, C., (2019). Motivational practice: Insights from the classroom. Studentlitteratur.
Illés, É. (2020). Understanding context in language use and teaching. Routledge.
In’nami, Y., Koizumi, R., & Tomita, Y. (2019). Meta-analysis in applied linguistics. In J. McKinley & H. Rose (Eds.), The Routledge handbook of research methods in applied linguistics (pp. 240-252). Routledge.
Jahedizadeh, S., & Al-Hoorie, A. (2021). Directed motivational currents: A systematic review. Studies in Second Language Learning and Teaching, 11, 517-541. https://doi.org/10.14746/ssllt.2021.11.4.3
Jin, S., & Lee, H. (2022). Willingness to communicate and its high-evidence factors: A meta-analytic structural equation modeling approach. Journal of Language and Social Psychology. https://doi.org/10.25384/SAGE.c.5950697.v1 
Larsen-Hall, J., & Plonsky, L. (2015). Reporting and interpreting quantitative research findings: What gets reported and recommendations for the field. Language Learning, 65, 127-159. https://doi.org/10.1111/lang.12115
Li, S. (2015). The associations between language aptitude and second language grammar acquisition: A meta-analytic review of five decades of research. Applied Linguistics, 36, 385-408.
Li, S., Shintani, N., & Ellis, R. (2012). Doing meta-analysis in SLA: Practice, choice, and standards. Contemporary Foreign Language Studies, 384(12), 1-17.
Li, S., & Wang, H. (2018). Traditional literature review and research synthesis. In A. Phakiti, P. De Costa, L. Plonsky & S. Starfield (Eds.), The Palgrave handbook of applied linguistics research methodology (pp. 123-144). Palgrave MacMillan.
Li, S., & Zhou, H. (2021). The methodology of the research on language aptitude: A systematic review. Annual Review of Applied Linguistics, 41, 25-54. https:// doi.org/10.1017/S0267190520000136
Lipsey, M. W., & Wilson, D. B. (2001). Practical meta-analysis. Sage Publications.
Mahmoodi, M. H., & Yousefi, M. (2021). Second language motivation research 2010-2019: A synthetic exploration. The Language Learning Journal, 1-24. https://doi.org/10.1080/09571736.2020.1869809
Masgoret, A.-M., & Gardner, R. C. (2003). Attitudes, motivation, and second language learning: A meta-analysis of studies conducted by Gardner and associates. Language Learning, 53, 123-163.
Maykut, P., & Morehouse, R. (2002). Beginning qualitative research: A philosophical and practical guide. Routledge.
Mendoza, A., & Phung, H. (2019). Motivation to learn languages other than English: A critical research synthesis. Foreign Language Annals, 52, 120-140.
Miles, M. B., Huberman, A. M., & Saldaña, J. (2018). Qualitative data analysis: A methods sourcebook. Sage Publications.
Norris, J. M., & Ortega, L. (2006). The value and practice of research synthesis for language learning and teaching. In J. M. Norris & L. Ortega (Eds.), Synthesizing research on language learning and teaching (pp. 3-50). John Benjamins.
Oswald, F. L., & Plonsky, L. (2010). Meta-analysis in second language research: Choices and challenges. Annual Review of Applied Linguistics, 30, 85-110.
Page, M. J., McKenzie, J. E., Bossuyt, P. M. et al. (2021). The PRISMA 2020 statement: An updated guideline for reporting systematic reviews. Systematic Reviews 10(89), 1-11. https://doi.org/10.1186/s13643-021-01626-4
Plonsky, L. (2011). The effectiveness of second language strategy instruction: A meta-analysis. Language Learning, 61, 993-1038.
Plonsky, L., & Oswald, F. L. (2012). How to do a meta-analysis. In A. Mackey & S. M. Gass (Eds.), Research methods in second language acquisition: A practical guide (pp. 275-295). Basil Blackwell.
Plonsky, L., & Oswald, F. L. (2014). How big is “big”? Interpreting effect sizes in L2 research. Language Learning, 64(4), 878-912. https://doi.org/10.1111/lang.12079
Qureshi, M. A. (2016). A meta-analysis: Age and second language grammar acquisition. System, 60, 147-160. https://doi.org/10.1016/j.system.2016.06.001.
Teimouri, Y., Goetze, J., & Plonsky, L. (2019). Second language anxiety and achievement: A meta-analysis. Studies in Second Language Acquisition, 41(2), 363-387. https://doi.org/10.1017/S0272263118000311
Yousefi, M., & Mahmoodi, M. H. (2022). The L2 motivational self-system: A meta-analysis approach. International Journal of Applied Linguistics https://doi.org/10.1111/ijal.12416
Zhang, X. (2019). Foreign language anxiety and foreign language performance: A meta-analysis. Modern Language Journal, 103, 763-781.
License
1.1 The Author hereby warrants that he/she is the owner of all the copyright and other intellectual property rights in the Work and that, within the scope of the present Agreement, the paper does not infringe the legal rights of another person. The owner of the copyright work also warrants that he/she is the sole and original creator thereof and that is not bound by any legal constraints in regard to the use or sale of the work.
1.2. The Publisher warrants that is the owner of the PRESSto platform for open access journals, hereinafter referred to as the PRESSto Platform.
2. The Author grants the Publisher non-exclusive and free of charge license to unlimited use worldwide over an unspecified period of time in the following areas of exploitation:
2.1. production of multiple copies of the Work produced according to the specific application of a given technology, including printing, reproduction of graphics through mechanical or electrical means (reprography) and digital technology;
2.2. marketing authorisation, loan or lease of the original or copies thereof;
2.3. public performance, public performance in the broadcast, video screening, media enhancements as well as broadcasting and rebroadcasting, made available to the public in such a way that members of the public may access the Work from a place and at a time individually chosen by them;
2.4. inclusion of the Work into a collective work (i.e. with a number of contributions);
2.5. inclusion of the Work in the electronic version to be offered on an electronic platform, or any other conceivable introduction of the Work in its electronic version to the Internet;
2.6. dissemination of electronic versions of the Work in its electronic version online, in a collective work or independently;
2.7. making the Work in the electronic version available to the public in such a way that members of the public may access the Work from a place and at a time individually chosen by them, in particular by making it accessible via the Internet, Intranet, Extranet;
2.8. making the Work available according to appropriate license pattern Attribution 4.0 International (CC BY 4.0) as well as another language version of this license or any later version published by Creative Commons.
3. The Author grants the Publisher permission to reproduce a single copy (print or download) and royalty-free use and disposal of rights to compilations of the Work and these compilations.
4. The Author grants the Publisher permission to send metadata files related to the Work, including to commercial and non-commercial journal-indexing databases.
5. The Author represents that, on the basis of the license granted in the present Agreement, the Publisher is entitled and obliged to:
5.1. allow third parties to obtain further licenses (sublicenses) to the Work and to other materials, including derivatives thereof or compilations made, based on or including the Work, whereas the provisions of such sub-licenses will be the same as with the Attribution 4.0 International (CC BY 4.0) Creative Commons sub-license or another language version of this license, or any later version of this license published by Creative Commons;
5.2. make the Work available to the public in such a way that members of the public may access the Work from a place and at a time individually chosen by them, without any technological constraints;
5.3. appropriately inform members of the public to whom the Work is to be made available about sublicenses in such a way as to ensure that all parties are properly informed (appropriate informing messages).
6. Because of the royalty-free provision of services of the Author (resulting from the scope of obligations stipulated in the present Agreement), the Author shall not be entitled to any author’s fee due and payable on the part of the Publisher (no fee or royalty is payable by the Publisher to the Author).
7.1. In the case of third party claims or actions for indemnity against the Publisher owing to any infractions related to any form of infringement of intellectual property rights protection, including copyright infringements, the Author is obliged to take all possible measures necessary to protect against these claims and, when as a result of legal action, the Publisher, or any third party licensed by the Publisher to use the Work, will have to abandon using the Work in its entirety or in part or, following a court ruling in a legal challenge, to pay damages to a third party, whatever the legal basis
7.2. The Author will immediately inform the Publisher about any damage claims related to intellectual property infringements, including the author’s proprietary rights pertaining to a copyrighted work, filed against the Author. of liability, the Author is obliged to redress the damage resulting from claims made by third party, including costs and expenditures incurred in the process.
7.3. To all matters not settled herein provisions of the Polish Civil Code and the Polish Copyright and Related Rights Act shall apply.