In slang, a troll is a person who posts or makes inflammatory, insincere, digressive, extraneous, or off-topic messages online (such as in social media, a newsgroup, a forum, a chat room, an online video game), or in real life, with the intent of provoking others into displaying emotional responses, or manipulating others' perception, thus acting as a bully or a provocateur. The behavior is typically for the troll's amusement, or to achieve a specific result such as disrupting a rival's online activities or purposefully causing confusion or harm to other people.
Researcher Ben Radford wrote about the phenomenon of clowns in history and the modern day in his book Bad Clowns, and found that "bad clowns" have evolved into Internet trolls. They do not dress up as traditional clowns but, for their own amusement, they tease and exploit "human foibles" in order to speak the "truth" and gain a reaction. Like clowns in make-up, Internet trolls hide behind "anonymous accounts and fake usernames". In their eyes, they are the trickster and are performing for a nameless audience via the Internet. Studies conducted in the fields of human–computer interaction and cyberpsychology by other researchers have corroborated Radford's analysis on the phenomenon of Internet trolling as a form of deception-serving entertainment and its correlations to aggressive behaviour, katagelasticism, black humor, and the Dark tetrad.
Trolling correlates positively with sadism, trait psychopathy, and Machiavellianism (see Dark triad). Trolls take pleasure from causing pain and emotional suffering. Their ability to upset or harm gives them a feeling of power. Psychological researches conducted in the fields of personality psychology and cyberpsychology report that trolling behaviour qualifies as an anti-social behaviour and is strongly correlated to sadistic personality disorder (SPD). Researches have shown that men, compared with women, are more likely to perpetrate trolling behaviour; these gender differences in online anti-social behaviour may be a reflection of gender stereotypes, where agentic characteristics such as competitiveness and dominance are encouraged in men. The results corroborated that gender (male) is a significant predictor of trolling behaviour, alongside trait psychopathy and sadism to be significant positive predictors. Moreover, these studies have shown that people who enjoy trolling online tend to also enjoy hurting other people in everyday life, therefore corroborating a longstanding and persistent pattern of psychopathological sadism.
A psychoanalytic and sexologic study on the phenomenon of Internet trolling asserts that anonymity increases the incidence of the trolling behaviour, and that "the internet is becoming a medium to invest our anxieties and not thinking about the repercussions of trolling and affecting the victims mentally and incite a sense of guilt and shame within them".