A few years ago, acting on a tip, school administrators at Great Neck North High School, a prominent, academically competitive public school in Long Island, took a closer look at students’ standardized test scores. Some of them seemed suspiciously high. What’s more, some of the high scorers had registered to take the test well outside their home district. When the Educational Testing Service conducted a handwriting analysis on the suspect exams, they concluded that the same person had taken multiple tests, registering each time under a different name. In November, 2011, twenty students from schools in Nassau County were arrested and accused of cheating. The arrests, combined with the social prominence of the school and its students, made the case one of the most prominent cheating scandals in recent history.

When a student sits down at a test, he knows how to cheat, in principle. But how does he decide whether or not he’ll actually do it? Is it logic? An impulse? A subconscious reaction to the adrenaline in his blood and the dopamine in his brain? People cheat all the time. But why, exactly, do they decide to do it in the first place?

One early theory, promoted by the psychologist Lawrence Kohlberg, held that cheating is governed by our moral development: the more advanced we are, the less likely we are to cheat. According to Kohlberg, we pass through six stages as we grow older, during which we become progressively less egotistical and more practiced at reasoning through the problems of morality. With each step in development, we become less likely to cheat. Cheating, in other words, is the result of a lack of moral fortitude and education. Later views contended that people cheat based on the situation. In 1996, the psychologist and economist George Loewenstein presented a cold, rational formula: people weigh the benefits of the unethical action against the costs of committing it, and decide accordingly. That same year, the psychologists David Messick and Max Bazerman countered with a less precise, more emotional approach, positing that cheating is the result of a highly subjective reasoning process that includes three types of argument: how we think about the world, how we think about other people, and how we think about ourselves. Eight years later, Bazerman offered an addendum to his initial view. For the most part, he said, our decision to cheat or not cheat occurs on a subconscious level. It’s a result of situational forces of which we are hardly, if at all, aware.

Most modern research on cheating explores the subtle behavioral influences that form the noisy background to our daily choices. In a typical laboratory set-up to measure cheating behavior, people are placed in a situation where they think their actions are anonymous and where there is no chance of getting caught. In reality, of course, what they do is observed. As it turns out, almost anyone will cheat when given even minor, consciously imperceptible behavioral cues. For instance, in a series of three experiments, a group of psychologists found that lighting could affect cheating. In one study, participants in a dimly-lit room cheated more often than those in a lighter one. While both groups performed equally well on a set of math problems, students in the darker room self-reported that they correctly solved, on average, four more problems than the other group—earning $1.85 more as a result, since they were being paid for each correct answer. The authors suggested that the darkness created an “illusory anonymity”: even though you aren’t actually more anonymous in the dark than in the light, you feel as though you are, making you more likely to engage in behaviors you otherwise wouldn’t.

Similar effects have been observed with a variety of situational factors that don’t seem directly related to cheating. We cheat more, for instance, when we’re in a messy environment—one that has more signs of socially deviant behavior, like litter, graffiti, and other rubble. We’re also more likely to cheat when we think there’s more to go around, since there are plenty of resources and we believe that our own behavior won’t have much of an impact. We cheat, too, when we’re simply exposed to a statement that highlights determinism—when we’re told that our behavior is a result of genes and the environment, as opposed to free will. When we are placed in a position of perceived power, the likelihood of cheating also goes up. New research from the psychologists Andy Yap, Dana Carney, and colleagues suggests that people who assume expansive power poses, such as standing with their feet shoulder-width apart and their hands on their hips, become, consciously or not, more likely to steal money or cheat on a test. When they sit in expansive car seats, which allow them to spread out, instead of constricting them as a tighter seat would, they become more likely to commit a traffic violation during a driving simulation—and, in a real-world version, cars with more expansive drivers’ seats were more likely to be illegally double-parked. One recent study, out last month in the journal Psychological Science, even suggests that the common societal values of power and achievement can lead to cheating in and of themselves: they create a competitive mindset that in turn makes us more likely to engage in unethical self-promotional behavior. The results echo earlier findings that “achievement” goals—a focus on results, rather than on understanding—as opposed to “mastery” goals, increase cheating.

We also cheat more when we’re feeling tired, either physically or mentally. In a 2011 study led by the cognitive psychologists Francesca Gino and Dan Ariely, researchers asked students to watch a video and either do nothing or actively ignore words that appeared on the screen at the same time. The students who made the effort to ignore the words cheated far more during a subsequent problem-solving task. Sleep deprivation led to similar results: individuals who were more tired became more likely to cheat in a work environment. We don’t cheat spontaneously when we’re sleepy or drained; it’s that, when the opportunity to cheat presents itself, we become increasingly more likely to take advantage of it, as our self-control is depleted. One possible reason for cheating on standardized tests? Most of them are held early in the morning on Saturdays, when students are at their sleep-deprived worst.

Most perniciously, cheating can become self-reinforcing. When we cheat, we have a tendency to rationalize the behavior. We can’t change the past, so we change our attitude and justify our actions. But that adjustment, while it may make us feel better, also makes us more likely to cheat again: we cheat, we rationalize it, we accept it, and we cheat once more. Recent research from Harvard University suggests that, in both hypothetical scenarios and real-world tasks, people who behave dishonestly are more likely to become morally disengaged from their environment and to forget moral rules, such as honor codes. Cheating, it seems, can cause a self-justifying temporary block on ethical information.