Case Study
research-methodology
A case study is an in-depth investigation of a single unit — a learner, a classroom, a teacher, a programme, or an institution. It aims for rich, contextualised understanding rather than generalisable findings. In SLA and applied linguistics, case studies have produced some of the field's most influential insights.
Defining Features
- Bounded unit — the case has clear boundaries (one learner, one class, one school)
- Multiple data sources — interviews, observations, tests, diaries, artefacts, recordings
- Contextual depth — the case is studied within its real-life context, not extracted from it
- Holistic analysis — aims to understand the complexity of the case, not to isolate variables
Landmark SLA Case Studies
| Study | Subject | Key Finding |
|---|---|---|
| Schumann (1978) | Alberto, a 33-year-old Costa Rican in the US | Social and psychological distance explained his pidginised, fossilised English. Founded the Acculturation model. |
| Schmidt (1983) | Wes, a 33-year-old Japanese artist in Hawaii | High communicative competence but low grammatical accuracy — challenged the assumption that social integration guarantees grammatical development. |
| Huebner (1983) | Ge, a Hmong speaker | Documented the emergence and reorganisation of the article system in naturalistic SLA over time. |
| Lardiere (1998, 2007) | Patty, a Chinese L1 speaker | Near-native comprehension but persistent morphological deficits after decades of immersion — evidence for the Missing Surface Inflection Hypothesis. |
Types of Case Study
- Intrinsic — the case itself is of primary interest (e.g., an exceptional learner)
- Instrumental — the case illuminates a broader issue (e.g., studying one classroom to understand Focus on Form)
- Collective/multiple-case — several cases studied for comparison (Stake, 1995; Yin, 2009)
Strengths
- Captures complexity and context that experimental designs strip away
- Reveals processes, not just outcomes — how and why, not just whether
- Can document rare or exceptional phenomena
- Generates hypotheses for larger-scale research
- Gives voice to individual learners, often lost in group averages
Limitations
- Generalisability — findings from one case may not transfer to others (though Stake argues for "naturalistic generalisation")
- Researcher subjectivity — interpretation depends heavily on the researcher's lens
- Time-intensive — sustained engagement with data collection and analysis
- Confirmability — difficult to replicate
Quality Criteria
Case study quality is evaluated by qualitative trustworthiness criteria: credibility (prolonged engagement, Triangulation, member checking), transferability (thick description enabling readers to judge applicability), dependability (audit trail), and confirmability (evidence grounding).
Key References
- Stake (1995) — The Art of Case Study Research
- Yin (2009) — Case Study Research: Design and Methods (4th ed.)
- Duff (2008) — Case Study Research in Applied Linguistics
- Duff (2014) — case study methodology in SLA, in The Routledge Handbook of SLA