Fun and enjoyment. as postulated by Ryan and Deci's Self Determination Theory, enjoyment of an activity may contribute to the enhancement of the intrinsic motivation of a person in doing the activity. Maybe you could refer to my article for a general idea.
Sorry forgot to link, here it is: https://www.researchgate.net/publication/319272458_SOCIAL_SCIENCES_HUMANITIES_The_Driven_Readers_amongst_Private_Higher_Education_Institution_Students_A_Case_Study
Article SOCIAL SCIENCES & HUMANITIES The Driven Readers amongst Priv...
I can suggest a few papers that may be useful to answer your question. I hope they help.
Don
Agawa, T., & Takeuchi, O. (2016). Re-examination of psychological needs and L2 motivation of japanese EFL learners: An interview study. Asian EFL Journal, 89, 74.
Buckledee, S. (2008). Motivation and second language acquisition. ELOPE: English Language Overseas Perspectives and Enquiries, 5(1-2), 159-170. doi:10.4312/elope.5.1-2.159-170
Carreira, J. M. (2011). Relationship between motivation for learning EFL and intrinsic motivation for learning in general among japanese elementary school s students. System, 39(1), 90-102. doi:10.1016/j.system.2011.01.009
For decades,the bulk of research addressing intrinsic motivation (IM) has revealed that it is a powerful engine for learner development. The psychological evidence related to IM supports the advantages it offers to SLA learners.For one thing, learners with intrinsic motivation enjoy a high level of grit- a persistent perseverance for attaining learning goals. Another thing is that by conscious engagement, such individuals make a better use of learning strategies and their cognitive abilities since they exploit their creative abilities more effectively.