seven hub sciences can be identified: mathematics, physics, chemistry, earth sciences, medicine, psychology, and the social sciences. Yes, psychology emerged as one of the hub disciplines of science!
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Figure 1. Map of science generated using a similarity measure based on co-citations. Large font size labels identify major areas of science. Small labels denote the disciplinary topics of nearby cluster sof journals. From Boyack et al. (2005).
Boyack, K.W., Klavans, R., & Börner, K. (2005). Mapping the backbone of science. Scientometrics, 64, 351-374.