What is the difference between the halo effect and the Pygmalion effect?

The halo effect is a cognitive bias where our overall impression of a person influences our perceptions of their specific traits. The Pygmalion effect, on the other hand, is a self-fulfilling prophecy where higher expectations lead to an increase in performance. In essence, the halo effect is about perceptions influencing judgments, while the Pygmalion effect is about expectations influencing outcomes.