Final answer:
Fear was the human emotion exploited both by the Salem Witch Trials and McCarthyism, leading to hysteria and false accusations in both instances.
Step-by-step explanation:
The human emotion exploited by both the Salem Witch Trials and McCarthyism was fear. Throughout history, fear has been a powerful tool for those seeking to control or manipulate populations. In the case of the Salem Witch Trials, fear of the supernatural and the Devil led to widespread hysteria and false accusations. Similarly, during McCarthyism in the 1950s, fear of Communism led to a nationwide scare where many people were unfairly accused and persecuted without substantial evidence.