By Aditya Shukla, psychologist, founder of Cognition Today
People are surprised when their expectations are violated. It then triggers your attention to focus on something new. It is proof that your attention is captured.
People get angry when they feel they have been treated poorly. So they use anger as a way to negotiate better treatment by threatening harm.
Fear directly comes from feeling a sense of threat. The body then quickly enters survival mode.
Disgust is a response to rotting smells which generally indicate food is unhealthy. It's an instinct to puke out so rotting food doesn't stay in the stomach to further hurt the body.
Sadness is a complex emotion, but researchers believe it primary purpose is to enter a low energy state and seek empathy for social help.
Joy, specifically, and not the philosophical idea of happiness, is a reward for the brain to repeat a behavior that helps in some way.