Debra Titone & Jason Gullifer (Language & Multilingualism Laboratory, Department of Psychology, McGill University)
Capitalizing on our communicative & neurocognitive diversity: A selective overview of why and how we study individual differences in language processing
Studies in psycholinguistics traditionally focus on assessing general principles of language processing in broad strokes by making statistical comparisons of experimental manipulations relative to group-level performance. In virtually all common statistical approaches (e.g., F1/F2 analyses, lme4 models with random slopes), individual variation among subjects is often modeled as a random factor, and swept under the rug. This is important if the goal is to demonstrate basic principles of processing that would apply to all people. However, variation among participants can often mask effects of interest, yielding null results or interpretations subject to confounding influences. At the same time, important individual differences can be measured and can guide language processing interesting ways. Statistical methods, such as linear mixed effects models, are becoming ubiquitous within the field, enabling researchers to more easily hypothesize about and model variability in subjects directly. Crucially, variability can be modeled not only as random effects but also as fixed effects that may continuously modulate processing.
Despite the importance of individual difference variables and the availability of computational methods to model them, many studies still focus on identifying basic principles of processing, and this focus may be getting us into hot water within some areas of research. For example, one highly contentious topic within psycholinguistics today is whether bilingualism confers benefits to executive functions, with some researchers demonstrating evidence for a “bilingual advantage” and others demonstrating null effects. However, research on this hypothesized effect (which if true, is likely very small statistically) is occurring in drastically different locations around the globe, likely with different patterns of bilingualism and language usage, yet these variables are often not accounted for in the models. Recent work on bilingual reading and executive functions in our lab highlights the importance of capturing this variation (e.g., Gullifer, et al., under review; Pivneva, Mercier, & Titone, 2014; Titone, et al., 2017; Subramaniapillai, Rajah, Pasvanis, & Titone, in press; Whitford & Titone, 2012).
Thus, in this course, our aim is to discuss the general notion of inidividual differences in language processing, and to offer a general approach for investigating individual differences that has evolved within our group over the years. In the first two lectures by Dr. Jason Gullifer, the general notion of individual differences is presented with examples from our ongoing work, along with the statistical approaches we tend to use (for which we welcome feedback from others). In the second two lectures by Dr. Debra Titone, ongoing work in our lab will be discussed that investigates real-time language processing (i.e., reading) and individual differences among bilinguals, as well as in a population less frequently studied within psycholinguistics, people with schizophrenia. The final day of the course will consist of a data blitz where students present their own research topics of interest that bear on the notion of individual differences in language processing to obtain feedback from the group.
Gullifer, J. W., Chai, X. J., Whitford, V., Pivneva, I., Baum, S., Klein, D., & Titone, D. (in revision). Bilingual Experience and Resting-State Brain Connectivity: Independent Contributions of L2 Age of Acquisition and Social Diversity of Language Use. Neuropsychologia.
Pivneva, I., Mercier, J., & Titone, D. (2014). Executive control modulates cross-language lexical activation during L2 reading: evidence from eye movements. Journal of Experimental Psychology: Learning, Memory, and Cognition, 40, 787–796.
Subramaniapillai, S., Rajah2, M. N., Pasvanis, S., Titone, D. (in press). Bilingual Experience and Executive Control over the Adult Lifespan: The Role of Biological Sex. Bilingualism: Language & Cognition.
Titone, D., Gullifer, J., Subramaniapillai, S., Rajah, N., & Baum, S. (2017). History-inspired reflections on the bilingual advantages hypothesis. In Bialystok, E. & Sullivan, M. D. (Eds.), Growing Old with Two Languages: Effects of Bilingualism on Cognitive Aging (pp. 265-295). Amsterdam: John Benjamins Publishing.
Whitford, V., & Titone, D. (2012). Second-language experience modulates first- and second-language word frequency effects: evidence from eye movement measures of natural paragraph reading. Psychonomic Bulletin & Review, 19, 73–80.