How Big Is “Big”? Interpreting Effect Sizes in L2 Research
Abstract
The calculation and use of effect sizes—such as d for mean differences and r for correlations—has increased dramatically in second language (L2) research in the last decade. Interpretations of these effects, however, have been rare and, when present, have largely defaulted to Cohen's levels of small ( d = .2, r = .1), medium (.5, .3), and large (.8, .5), which were never intended as prescriptions but rather as a general guide. As Cohen himself and many others have argued, effect sizes are best understood when interpreted within a particular discipline or domain. This article seeks to promote more informed and field‐specific interpretations of d and r by presenting a description of L2 effects from 346 primary studies and 91 meta‐analyses ( N > 604,000). Results reveal that Cohen's benchmarks generally underestimate the effects obtained in L2 research. Based on our analysis, we propose a field‐specific scale for interpreting effect sizes, and we outline eight key considerations for gauging relative magnitude and practical significance in primary and secondary studies, such as theoretical maturity in the domain, the degree of experimental manipulation, and the presence of publication bias.
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Plonsky and Oswald (2014) offered field-specific benchmarks for interpreting correlation coefficients: .25 small, .40 medium, and .60 large.
“Recently, Plonsky and Oswald (2014) have offered recommendations for field-specific benchmarks for interpreting the size of correlation coefficients: .25 small, .40medium, and .60 large.”
From The L2 motivational self system: A meta-analysis (2018) · cites this paper as Plonsky and Oswald (2014)
For speech rate, effect sizes were large across the first three performances only and small to medium from the fourth through fifth performance.
“However, the effect size was large according to the criteria posited by Plonsky and Oswald (2014) across the first three performances only and small to medium thereafter through the fifth performance”
From TASK REPETITION AND SECOND LANGUAGE SPEECH PROCESSING (2017) · cites this paper as Plonsky and Oswald (2014)
The effect of aural-oral task repetition on clause-final pausing was relatively small and limited to the first two task performances.
“The effect of aural-oral task repetition on clause-final pausing was relatively small according Plonsky and Oswald (2014) and limited to the first two task performances”
From TASK REPETITION AND SECOND LANGUAGE SPEECH PROCESSING (2017) · cites this paper as Plonsky and Oswald (2014)
The effects of aural-oral task repetition on mid-clause pausing persisted until the fourth performance, with effect sizes decreasing from medium to small.
“Thus, the effects of aural-oral task repetition on mid-clause pausing did not dissipate until the fourth performance but the effect size decreased from medium to small (Plonsky and Oswald, 2014)”
From TASK REPETITION AND SECOND LANGUAGE SPEECH PROCESSING (2017) · cites this paper as Plonsky and Oswald, 2014
For self-repairs, differences between performance 5 and performances 1 and 2, and between performance 6 and performances 1, 2, and 3 were statistically significant, though effect sizes were small according to Plonsky and Oswald (2014).
“However, the differences between the fifth repetition and the first two performances 1-5 (p = .017,d = 0.45), 2-5 (p = .01,d = 0.48), and the differences between the sixth performance and the first three performances were significant: 1-6 (p = .017,d = 0.50), 2-6 (p = .015,d = 0.51), 3-6 (p = .020,d = 0.49) although the effect sizes were small according to Plonsky and Oswald (2014).”
From TASK REPETITION AND SECOND LANGUAGE SPEECH PROCESSING (2017) · cites this paper as Plonsky and Oswald (2014)
The effect size for the first repetition on mid-clause filled pauses was larger than the other repetitions but still small according to the benchmarks of Plonsky and Oswald (2014).
“Although the effect size for the first repetition was larger than the others, it was still small according to the benchmarks proposed by Plonsky and Oswald (2014).”
From TASK REPETITION AND SECOND LANGUAGE SPEECH PROCESSING (2017) · cites this paper as Plonsky and Oswald (2014)
Enjoyment at T1 was significantly and positively associated with FL achievements at T2-T4, with small-to-medium effect sizes.
“As hypothesized, enjoyment at T1 was significantly and positively associated with FL achievements at T2 -T4, with small-to-medium effect sizes (Plonsky & Oswald, 2014).”
From Anxiety, enjoyment, and boredom in language learning amongst junior secondary students in rural China: How do they contribute to L2 achievement? (2023) · cites this paper as Plonsky & Oswald, 2014
For between-groups designs in L2 research, d values around 0.40 are a small effect size, around 0.70 a medium effect size, and around 1.00 a large effect size.
“For studies with a between-groups design, d values around 0.40 as a small effect size, values around 0.70 as a medium effect size, and values around 1.00 as a large effect size”
From Second language (L2) gains through digital game-based language learning (DGBLL): A meta-analysis (2022) · cites this paper as Plonsky and Oswald (2014)
Using Plonsky and Oswald's (2014) L2 research benchmarks, learners can generally expect small to medium positive effects on learning outcomes in DGBLL contexts.
“These findings suggest that, using Plonsky and Oswald's (2014) L2 research benchmarks, learners can generally expect small to medium positive effects on learning outcomes in DGBLL contexts.”
From Second language (L2) gains through digital game-based language learning (DGBLL): A meta-analysis (2022) · cites this paper as Plonsky and Oswald's (2014)
For within-group designs in L2 research, d values around 0.60 are a small effect size, around 1.00 a medium effect size, and around 1.40 a large effect size.
“For studies with a within-group design, d values around 0.60 as a small effect size, values around 1.00 as a medium effect size, and values around 1.40 as a large effect size”
From Second language (L2) gains through digital game-based language learning (DGBLL): A meta-analysis (2022) · cites this paper as Plonsky and Oswald (2014)
The effect size for the difference in grammatical accuracy was 0.56, which is between small (0.4) and medium (0.7) according to Plonsky and Oswald's (2014) guidelines.
“The effect size value was 0.56, which signifies an effect size between small (0.4) and medium (0.7) according to Plonsky and Oswald's (2014) effect size guidelines for L2 research.”
From Examining the impact of Grammarly on the quality of mobile L2 writing (2021) · cites this paper as Plonsky and Oswald's (2014)
Cites
Methods of Meta-Analysis: Correcting Error and Bias in Research Findings
Schmidt, F. L., & Hunter, J. E. (2015) · doi:10.4135/9781483398105 · Cited by 5,542 · see citing works
Effect size estimates: Current use, calculations, and interpretation.
Fritz, C. O., Morris, P. E., & Richler, J. J. (2012) · Journal of Experimental Psychology: General · doi:10.1037/a0024338 · Cited by 5,199 · see citing works
The Handbook of Research Synthesis and Meta-Analysis
(2019) · doi:10.7758/9781610448864 · Cited by 4,553 · see citing works
The earth is round (p < .05).
Cohen, J. (1994) · American Psychologist · doi:10.1037/0003-066x.49.12.997 · Cited by 4,003 · see citing works
The New Statistics: Why and How
Cumming, G. (2014) · Psychological Science · doi:10.1177/0956797613504966 · Cited by 3,200 · see citing works
Hunter, J., & Schmidt, F. (2004) · doi:10.4135/9781412985031 · Cited by 3,023 · see citing works
Morris, S. B., & DeShon, R. P. (2002) · Psychological Methods · doi:10.1037/1082-989x.7.1.105 · Cited by 2,502 · see citing works
Effectiveness of L2 instruction: A research synthesis and quantitative meta-analysis
Norris, J. M., & Ortega, L. (2000) · Language Learning · doi:10.1111/0023-8333.00136 · Cited by 2,414 · see citing works
Lipsey, M. W., & Wilson, D. B. (1993) · American Psychologist · doi:10.1037/0003-066x.48.12.1181 · Cited by 2,033 · see citing works
One Hundred Years of Social Psychology Quantitatively Described
Richard, F. D., Bond, C. F., & Stokes-Zoota, J. J. (2003) · Review of General Psychology · doi:10.1037/1089-2680.7.4.331 · Cited by 1,558 · see citing works
A systematic review and meta-analysis of the cognitive correlates of bilingualism
Adesope, O. O., Lavin, T., Thompson, T., & Ungerleider, C. (2010) · Review of Educational Research · doi:10.3102/0034654310368803 · Cited by 1,132 · see citing works
Effects of learning skills interventions on student learning: a meta-analysis.
Hattie, J., Biggs, J., & Purdie, N. (1996) · Review of Educational Research · doi:10.3102/00346543066002099 · Cited by 1,106 · see citing works
Tamim, R. M., Bernard, R. M., Borokhovski, E., Abrami, P. C., & Schmid, R. F. (2011) · Review of Educational Research · doi:10.3102/0034654310393361 · Cited by 1,029 · see citing works
The effectiveness of corrective feedback in SLA: A meta-analysis
Li, S. (2010) · Language Learning · doi:10.1111/j.1467-9922.2010.00561.x · Cited by 941 · see citing works
ORAL FEEDBACK IN CLASSROOM SLA: A Meta-Analysis
Lyster, R., & Saito, K. (2010) · Studies in Second Language Acquisition · doi:10.1017/s0272263109990520 · Cited by 838 · see citing works
Interactions between type of instruction and type of language feature: A meta-analysis
Spada, N., & Tomita, Y. (2010) · Language Learning · doi:10.1111/j.1467-9922.2010.00562.x · Cited by 746 · see citing works
Reporting standards for research in psychology: why do we need them? What might they be?
APA Publications and Communications Board Working Group on Journal Article Reporting Standards (2008) · American Psychologist · doi:10.1037/0003-066x.63.9.839 · Cited by 571 · see citing works
Quantitative Research Methods, Study Quality, and Outcomes: The Case of Interaction Research
Plonsky, L., & Gass, S. (2011) · Language Learning · doi:10.1111/j.1467-9922.2011.00640.x · Cited by 267 · see citing works
Self-citationMeta-analysis in Second Language Research: Choices and Challenges
Oswald, F. L., & Plonsky, L. (2010) · Annual Review of Applied Linguistics · doi:10.1017/s0267190510000115 · Cited by 237 · see citing works
Self-citationA Meta-Analysis of Extensive Reading Research
Nakanishi, T. (2015) · TESOL Quarterly · doi:10.1002/tesq.157 · Cited by 184 · see citing works
Effect sizes in cumulative meta-analyses of mental health randomized trials evolved over time
Trikalinos, T. A., Churchill, R., Ferri, M., Leucht, S., Tuunainen, A., Wahlbeck, K., & Ioannidis, J. P. A. (2004) · Journal of Clinical Epidemiology · doi:10.1016/j.jclinepi.2004.02.018 · Cited by 177 · see citing works
Shintani, N., Li, S., & Ellis, R. (2013) · Language Learning · doi:10.1111/lang.12001 · Cited by 117 · see citing works
1. The value and practice of research synthesis for language learning and teaching
Norris, J. M., & Ortega, L. (2006) · Language Learning & Language Teaching · doi:10.1075/lllt.13.04nor · Cited by 72 · see citing works
Flagged first, then by citations
Cited by
Sorted by citations
Foreign language enjoyment and anxiety: The effect of teacher and learner variables
Dewaele, J.-M., Witney, J., Saito, K., & Dewaele, L. (2018) · Language Teaching Research · doi:10.1177/1362168817692161 · Cited by 780 · see citing works
Exploring the potential of using an AI language model for automated essay scoring
Mizumoto, A., & Eguchi, M. (2023) · Research Methods in Applied Linguistics · doi:10.1016/j.rmal.2023.100050 · Cited by 647 · see citing works
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Teimouri, Y., Goetze, J., & Plonsky, L. (2019) · Studies in Second Language Acquisition · doi:10.1017/s0272263118000311 · Cited by 611 · see citing works
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Teimouri, Y., Plonsky, L., & Tabandeh, F. (2022) · Language Teaching Research · doi:10.1177/1362168820921895 · Cited by 503 · see citing works
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Dewaele, J.-M., & Alfawzan, M. (2018) · Studies in Second Language Learning and Teaching · doi:10.14746/ssllt.2018.8.1.2 · Cited by 418 · see citing works
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Al-Hoorie, A. H. (2018) · Studies in Second Language Learning and Teaching · doi:10.14746/ssllt.2018.8.4.2 · Cited by 351 · see citing works
Li, C., & Wei, L. (2023) · Studies in Second Language Acquisition · doi:10.1017/s0272263122000031 · Cited by 317 · see citing works
“As hypothesized, enjoyment at T1 was significantly and positively associated with FL achievements at T2–T4, with small-to-medium effect sizes (Plonsky & Oswald, 2014).”
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DEWAELE, J., MAGDALENA, A. F., & SAITO, K. (2019) · The Modern Language Journal · doi:10.1111/modl.12555 · Cited by 301 · see citing works
Dewaele, J.-M., & Dewaele, L. (2017) · Journal of the European Second Language Association · doi:10.22599/jesla.6 · Cited by 285 · see citing works
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Lambert, C., Kormos, J., & Minn, D. (2017) · Studies in Second Language Acquisition · doi:10.1017/s0272263116000085 · Cited by 281 · see citing works
Link, S., Mehrzad, M., & Rahimi, M. (2022) · Computer Assisted Language Learning · doi:10.1080/09588221.2020.1743323 · Cited by 275 · see citing works
Dewaele, J.-M., & Dewaele, L. (2020) · Studies in Second Language Learning and Teaching · doi:10.14746/ssllt.2020.10.1.3 · Cited by 202 · see citing works
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Proietti Ergün, A. L., & Dewaele, J.-M. (2021) · System · doi:10.1016/j.system.2021.102506 · Cited by 166 · see citing works
Tanner-Smith, E. E., Durlak, J. A., & Marx, R. A. (2018) · Prevention Science · doi:10.1007/s11121-018-0942-1 · Cited by 140 · see citing works
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Kim, S. K., & Webb, S. (2022) · Language Learning · doi:10.1111/lang.12479 · Cited by 119 · see citing works
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Nakata, T., & Suzuki, Y. (2019) · Studies in Second Language Acquisition · doi:10.1017/s0272263118000219 · Cited by 78 · see citing works
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van den Broek, G. S. E., Takashima, A., Segers, E., & Verhoeven, L. (2018) · Language Learning · doi:10.1111/lang.12285 · Cited by 67 · see citing works
“An effect size of this magnitude is considered small in L2 research (Plonsky & Oswald, 2014).”
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Zou, B., Wang, C., Yan, Y., Du, X., & Ji, Y. (2025) · International Journal of Applied Linguistics · doi:10.1111/ijal.12658 · Cited by 66 · see citing works
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“In this meta-analysis, we interpreted the effect sizes using the benchmarks suggested by Plonsky and Oswald (2014) for L2 research:”
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KASPROWICZ, R. E., MARSDEN, E., & SEPHTON, N. (2019) · The Modern Language Journal · doi:10.1111/modl.12586 · Cited by 47 · see citing works
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Self-citationGao, J., & Ma, S. (2021) · Studies in Second Language Acquisition · doi:10.1017/s0272263120000686 · Cited by 8 · see citing works
Suzuki, S., Takatsu, H., Matsuura, R., Koyama, M., Saeki, M., & Matsuyama, Y. (2025) · Language Testing · doi:10.1177/02655322251348725 · Cited by 6 · see citing works
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- Authors
- Plonsky, L., & Oswald, F. L.
- Affiliations
- Northern Arizona University (US)
- Rice University (US)
- Corresponding author
- Plonsky, Luke
- Venue
- Language Learning
- Publisher
- Wiley
- Published
- 2014-10-15
- Volume
- 64
- Issue
- 4
- Pages
- 878-912
- ISSN
- 0023-8333 (ISSN-L)
- 1467-9922
- OpenAlex
- W2124812340
- Cited by
- 1,960
- References
- 23
- Citations by year
- 2026: 223 · 2025: 292 · 2024: 245 · 2023: 238 · 2022: 218 · 2021: 190 · 2020: 213 · 2019: 123 · 2018: 84 · 2017: 59 · 2016: 45 · 2015: 25 · 2014: 4 · 2013: 1
- FWCI
- 43.39
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Language Learning (publishedVersion)
- UCL Discovery (University College London) (submittedVersion)
- Topics
- Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
- Social Sciences › Arts and Humanities › Language and Linguistics › EFL/ESL Teaching and Learning
- Social Sciences › Education › Educational Research and Methods
- Keywords
- effect size interpretation, Cohen's d, second language research, practical significance, publication bias, meta-analysis, experimental manipulation
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