Why you need to know this: if there is somebody at work who is pointlessly unpleasant in small, deniable ways, this explains what is probably driving it, and the answer is not the one you are carrying.
Most people, asked why a colleague is cruel, reach for one of two explanations, and both of them are about feeling. Either the person is angry about something, or the person is under pressure and taking it out on whoever is nearest.
The best-evidenced trigger in this literature is neither. It is boredom.
The finding is unusually strong for this field. A team led by Stefan Pfattheicher ran nine studies on 7,617 people, and after establishing that people who report being chronically bored also report more enjoyment of others’ discomfort, they went further and made people bored on purpose. Boredom raised cruel behaviour in every experiment they ran.
The condition that makes it useful. When participants had several other things to do instead, boredom produced cruelty only among those already high in the trait. When nothing else was available, it produced cruelty across the board, including among people who scored at the very bottom of the scale. That is a finding about the situation rather than about the person, which is the first reason this is worth your twenty minutes.
The second reason is that it does not work. Across 120 employees reporting twice a day for ten working days, a bored day was followed by a worse-behaved day, and a worse-behaved day was followed by a more bored day (Kim, Kaplan, Aitken & Ponce, 2024). Whatever the stimulation buys, it buys it for less than a day, and it charges interest.
The third reason is cost rather than character. In the study that first put everyday sadism on the map, when hurting an innocent person required no effort, several unpleasant traits predicted doing it; when it first required a tedious piece of work, only sadism did (Buckels, Jones & Paulhus, 2013). The price of the act separates the many from the few, making friction, rather than screening, the lever an organisation actually has.
Three more findings sit alongside those, and one of them is an absence. A 2026 review of dark personality and workplace bullying screened eighty-nine records, included sixteen studies and pooled nine, producing figures for psychopathy, narcissism and Machiavellianism; the one trait defined by enjoying harm was left out of the pooled analysis altogether, because there were not enough workplace studies of it to pool (Sui, Malik, Tiliopoulos & Yu, 2026). Among 613 employees, feeling fairly treated changed how Machiavellian people behaved towards colleagues and did not change how sadistic people behaved at all (Fernández-del-Río, Castro & Ramos-Villagrasa, 2022). Across twenty-four studies of 14,044 people in eleven countries, sadism was the strongest of the four dark traits at predicting online trolling, and narcissism the weakest (Hidalgo-Fuentes, González-Pérez & Martínez-Álvarez, 2025).
The rest of this article traces why cheapness rather than character is the operative variable, what boredom actually is inside an organisation, who you will wrongly accuse if you stop reading here, and what an organisation can do that the evidence supports.