The present research employed a dynamic approach to language learning and traced the co-development of English language learners’ private and social foreign language enjoyment(FLE). To this aim, a factor of curves model (FCM) was used, as an innovative statisticalprocedure, to trace the covariance of the subdomains of FLE longitudinally on fourmeasurement occasions and to explore the covariance of the initial state and slope of the sub-domains of FLE and how variation in private and social FLE can be explained by theunderlying global factor of FLE. For data collection, the FLE scale developed by Dewaele andMacIntyre (2014) was distributed to 437 adult EFL learners in four phases. The data wereanalyzed in Mplus in three steps suggested by Wickrama et al (2016). The results indicatedthat all growth parameters across the two primary growth curves (intercepts and slopes ofprivate FLE and social FLE) were statistically significant. This confirmed the existence ofsufficient inter-individual variation and intra-individual trend within each subdomain of FLEand a significant increase over time in these subdomains. Also, the primary growth factors ofprivate FLE and social FLE differentially contributed to second-order growth factors of FLE.Finally, the variances of the intercept and slope of each second subdomain were revealed tobe largely explained by the global factor of FLE. These findings were discussed in the light ofthe potential variables associated with FLE.Keywords: foreign language enjoyment, private FLE, social FLE, factor of curves model,parallel process modelin
