Individual Differences in SLA

Individual differences (IDs) in SLA refer to the range of cognitive, affective, and personality variables that cause learners exposed to the same input and instruction to achieve different outcomes. Understanding IDs explains why a single classroom can produce such varied levels of attainment and why no single teaching method works equally well for all learners.

Major ID Variables

Variable	Domain	Key finding
Language Aptitude	Cognitive	Strongest single predictor of L2 learning rate. Carroll & Sapon (1959), Skehan (1998)
Motivation	Affective	Integrative Motivation and Instrumental Motivation both predict sustained effort and attainment. Gardner & Lambert (1972), Dörnyei (2005)
Working Memory	Cognitive	Predicts success especially under explicit learning conditions. Baddeley (2000)
Language Anxiety	Affective	Debilitating anxiety specific to L2 use impairs performance. Horwitz et al. (1986)
Age	Biological	Earlier exposure generally advantages pronunciation; the Critical Period Hypothesis remains debated
Willingness to Communicate	Affective/social	Determines how much L2 use a learner actually engages in: input and output volume
Learning style	Cognitive	Preferences for visual, auditory, kinaesthetic processing; empirical support is weaker than commonly assumed
Personality	Affective	Extraversion, openness, and tolerance of ambiguity correlate with some L2 outcomes
Beliefs about learning	Metacognitive	Learner beliefs about how languages are learned shape strategy choice and effort

Why IDs Matter

The same instructional input produces different outcomes because learners differ in:

1. How they process input: WM capacity, analytic ability, phonological memory
2. How much input they seek: WTC, motivation, anxiety level
3. How they respond to instruction: aptitude–treatment interactions mean that explicit instruction benefits some learners more than others
4. How they sustain effort: motivation, self-regulation, grit

Dörnyei's L2 Motivational Self System

Dörnyei (2005, 2009) reconceptualised L2 motivation around three components:

• Ideal L2 self: the learner's vision of themselves as a proficient L2 user
• Ought-to L2 self: external pressures and expectations
• L2 learning experience: the immediate impact of the learning environment, teacher, and materials

This framework shifted motivation research from static trait models toward dynamic, situated accounts.

Aptitude–Treatment Interaction (ATI)

A central finding in ID research: the effectiveness of a teaching approach depends on the learner's aptitude profile. High-analytic learners benefit from explicit instruction; learners with strong phonological memory may thrive in implicit, input-rich environments. This argues against one-size-fits-all methodology.

Teaching Implications

• Varied instructional approaches within a course accommodate different ID profiles
• Learner training in learning strategies and metacognitive strategies can compensate for weaker aptitude areas
• Anxiety management (supportive classroom climate, low-stakes practice) benefits learners with high language anxiety
• Motivation is not fixed; it can be cultivated through goal-setting, identity work, and engaging materials
• Assessment should account for ID-related variation; timed tests disadvantage learners with lower WM capacity or higher anxiety

References

• Dörnyei, Z. (2005). The psychology of the language learner. Lawrence Erlbaum.
• Dörnyei, Z. (2009). The L2 motivational self system. In Z. Dörnyei & E. Ushioda (Eds.), Motivation, language identity and the L2 self (pp. 9–42). Multilingual Matters.
• Robinson, P. (Ed.) (2002). Individual differences and instructed language learning. John Benjamins.
• Skehan, P. (1989). Individual differences in second-language learning. Edward Arnold.