Our goal is to establish a science of the individual, grounded in dynamic systems, and focused on the analysis of individual variability. Our argument is that individuals behave, learn, and develop in distinctive ways, showing patterns of variability that are not captured by models based on statistical averages. As such, any meaningful attempt to develop a science of the individual necessarily begins with an account of the individual variability that is pervasive in all aspects of behavior, and at all levels of analysis. Using examples from fields as diverse as education and medicine, we show how starting with individual variability, not statistical averages, helped researchers discover two sources of ordered variability-pathways and contexts-that have implications for theory, research, and practice in multiple disciplines. We conclude by discussing three broad challenges-data, models, and the nature of science-that must be addressed to ensure that the science of the individual reaches its full potential.

Most research on dyslexia to date has focused on early childhood, while comparatively little is known about the nature of dyslexia in adolescence. The current study had two objectives. The first was to investigate the relative contributions of several cognitive and linguistic factors to connected‐text oral reading fluency in a sample of adolescents with dyslexia (n = 77). The second was to test the hypothesis that the effect of verbal working memory on connected‐text oral reading fluency is moderated by word‐level skills and/or vocabulary knowledge. The results suggest that many deficits associated with childhood dyslexia remain prominent in adolescence, but the nature of the relationships between key cognitive and linguistic predictors (i.e., word‐level reading, vocabulary, verbal working memory) and reading fluency appear to be different in adolescence. For example, while word‐level skills remain a significant predictor, the strength of the effect is relatively weak. In contrast, the data support an increased role for vocabulary and verbal working memory, including an interaction between these factors. The presence of an interaction can be interpreted as evidence that the influence of verbal working memory on connected‐text oral reading fluency in adolescents with dyslexia depends on individual differences in vocabulary knowledge. These results offer support for the changing nature of dyslexia across development, and suggest that researchers should study dyslexia in adolescents on its own terms, rather than treating it as an extension of reading problems in early childhood.