Short answers, pulled from the story.
William James declared in 1884 that we feel sad because we cry rather than cry because we are sad. He argued that physical reactions like trembling and racing hearts precede and create the mental state of emotion. This James-Lange theory posits that the perception of bodily changes is the emotion itself.
The limbic system serves as the command center for primal states and includes the amygdala and hippocampus. The amygdala acts as a rapid threat detector that releases hormones to trigger fight-or-flight responses. This system evolved from the olfactory senses of night-active mammals and links emotions to memory.
Paul Ekman found that the Fore people of Papua New Guinea displayed identical facial expressions for anger, disgust, fear, happiness, sadness, and surprise as Americans. His research demonstrated that these six basic emotions are universal and biologically hardwired rather than culturally relative. Ekman later expanded the list to include amusement, awe, contentment, and desire.
David Hume delivered a revolutionary argument in 1773 stating that reason is the slave of the passions. He wrote in A Treatise of Human Nature that reason alone can never be a motive to any action of the will. This idea challenged the ancient Greek ideal of dispassionate reason and suggested emotions are essential motivators of human conduct.
Neuroscientist Lisa Feldman Barrett proposed in the 21st century that emotions are constructed by the brain rather than triggered by the world. She argues that emotions emerge from the physical properties of the body, a flexible brain, and the specific culture and upbringing of the individual. This theory suggests that anxiety is not a universal response but a socially constructed experience.
Emotional memories are reactivated more frequently and remembered better than neutral memories due to the role of the amygdala. The amygdala links emotional states to specific memories within the limbic system. Research shows that traumatic emotions can be passed from parents to offspring to second and even third generation through transgenerational trauma.