Math plays a large role in psychology, statistics, in particular, Many psychological tests are interpreted as number such as percentiles, averages, median, and means. Math is an integral part of psychological research and experimentation. If you've ever heard a statement claiming results are accurate within plus or minus a certain number, that accuracy has been computed using probability and statistics. IQ is measured mathemtically, as well as child development and learning in humans and some animals. Pavlov's experiments with dogs and B.F. Skinner and his rats relied on math to determine and explain how well those animals were able to learn. It's all part of psychology.
