Obituary and tributes: William Alvin Mason (1926−2023).

This article is an obituary and tribute to William Alvin Mason, a prominent figure in the field of primatology. The article highlights Mason's significant contributions to primatology, psychology, and animal behavior, as well as his mentorship of many scientists. Mason's research focused on surrogate mother research, developmental psychobiology, and the study of titi monkeys. He authored or coauthored over 200 papers and held leadership positions in scientific societies. The text is a collection of personal reflections and tributes from individuals who had a close relationship with Mason, expressing gratitude for his guidance, support, and intellectual contributions. They remember him as a kind and humble individual who made a significant impact on their lives and careers. [Extracted from the article]