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Violence has not only always played a role in our evolution and development, but our own brains actually reward it. "We have found that the reward pathway in the brain becomes engaged in response to an aggressive event and that dopamine is involved," adds Kennedy.

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Put simply, we steal because we need to, or for the thrill of it. Indeed, participants in a study who were given naltrexone (a drug to curb addictive behavior) experienced a reduction in the urge to steal, when compared to those who took a placebo.

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We are creatures of habit and tend to hold on to bad ones as well, often finding a myriad of justifications as to why they won't affect us and why we’re the exception. According to Cindy Jardine of the University of Alberta, the reasons to do so include “innate human defiance, need for social acceptance, inability to truly understand the nature of risk, individualistic view of the world and the ability to rationalize unhealthy habits, and a genetic predisposition to addiction.”

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Humans lie all the time. The reasons for this vary, depending on the context, but we all lie in our daily lives. A few white lies here and there may not be harmful, but we can really cause harm by lying. Interestingly, animals are also capable of deception.

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Infidelity often happens for two reasons: dissatisfaction with one’s sex life (i.e. boredom) or because the person is unhappy in the relationship. This is not to say these are the only reasons, of course; they are just the most common ones.

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Bullying can be very destructive and indeed is present in various settings, from schools to workplaces. While the underlying reasons why we bully vary, it’s usually done to gain status, dominance, and power.

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Our thirst for violence is inherent to our species. "Aggression occurs among virtually all vertebrates and is necessary to get and keep important resources such as mates, territory and food," says professor Craig Kennedy.

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We tend to be sexually attracted (in the short term, at least) to people who display “dark triad” personality traits, namely narcissism, psychopathy, and Machiavellianism. Interestingly, a 2016 study also found that women who preferred “high narcissistic men's faces” had more children.

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This duality of virtue is also observed in the actor-observer asymmetry, a type of bias in which we tend to attribute other people’s bad deeds to their characters, while we would blame situational influences when the same deeds are performed by ourselves.

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You have probably come across comments and discussions on social media that made you cringe. Perhaps you may have even engaged in one or two. This is due to the online disinhibition effect, where we feel safe and entitled to say whatever we want, without the repercussions we would have to face if we were to say it in person to someone.

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Just look back in history and you will find evidence of this; be it political leaders or CEOs. Many leaders score highly on psychopathic traits, and we are naturally attracted to their confidence and other traits.

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Moral hypocrisy comes naturally for many of us. Participants in a study rated the same selfish behavior as fairer when it was done by themselves, and less fair when done by others.

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Similarly, acts of rudeness are more harshly criticized when they’re done by strangers rather than by ourselves or those close to us (i.e. friends and family).

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“This finding suggests that people may seek to ameliorate the negative effects of a disaster when there are shared characteristics between the disaster and the self.” This is a clear example of implicit egotism.

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Another study found that the majority of participants much preferred being entertained, even if alone. They derived more pleasure from doing solitary everyday activities, such as reading or watching TV, over thinking.

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Humans tend to be overconfident and have an inflated view of their abilities and attributes.

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A 2008 study looked at donations to disaster relief events and found that “individuals who shared an initial with the hurricane name were overrepresented among hurricane relief donors relative to the baseline distribution of initials in the donor population.”

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A study conducted by the University of Southampton in an English jail found that prisoners rated themselves as having more pro-social characteristics (i.e. kindness to others, trustworthiness, honesty, etc.), and as being as law-abiding as those outside of prison.

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Many of us can’t stand being alone with our own thoughts. In fact, a 2004 study found that a group of people would rather receive electric shocks than spend 15 minutes contemplating things on their own. The number was higher among male participants, with 67% choosing to do so, in comparison to 25% of female participants.

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We tend to be overconfident about our understanding of topics and may view our opinions as superior to those of others.

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A 1967 study found that participants who were in favor of, or against, the death penalty ignored any facts that contradicted their views, and did not change their opinion. This is because doing so would undermine their sense of identity.

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In a study, a woman was punished with electric shocks for wrong answers. She was rated as less likeable by female participants when they learned that they would witness her getting shocked again (and not have the option to minimize her suffering).

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Devaluing the woman was a way to make the study participants feel less bad about their powerlessness to minimize her suffering.

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According to professor Leo Montada’s analysis of Melvin Lerner's work ‘Belief in a Just World,’ “Blaming innocent victims becomes understandable [...] people want to believe that the world is a just one where everyone gets what they deserve even if the immediately available observations and information challenge this view.”

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A study found that a group of six-year-olds chose to pay money to watch an antisocial puppet get hit, rather than use the money to purchase stickers.

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Schadenfreude is a word borrowed from German that doesn’t have a direct translation to English. It’s used to describe the experience of deriving pleasure or joy from another person's suffering or misfortune.

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A 2013 study found that children as young as four experience a small degree of schadenfreude, particularly if they perceived the person deserved it. It’s worth mentioning that by age three kids already keep track of whether others are in debt to them.

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Tragically, we tend to think of outsiders and minorities as less human than us. A study has found that participants showed less neural activity "associated with thinking about people" when they were exposed to images of homeless people and drug addicts.

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While there are socio-cultural aspects in many of these dehumanization behaviors, we do start to do so early in our lives. In two studies, five and six-year-olds were shown “a set of ambiguous doll-human face morphs” and asked which they viewed as more human. Those from different backgrounds (from a different city or sex than the child) were viewed as less human.

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Some primates also display bullying behavior, so scientists suspect that there might be some evolutionary purpose for it.

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Another study found that young people tend to dehumanize older people. Similarly, research shows that drunk women tend to be dehumanized by both men and women.

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Being human is indeed an extraordinary experience, but have you ever wondered if we are inherently good or bad? Sure, there are a number of socio-cultural and circumstantial aspects to take into account that will influence the way we think and act, but, stripped of all external factors, what are we really like? Indeed, there are human behaviors that are naturally darker than others, and science has proven time and again that we're flawed by default.

In this gallery, we explore the dark side of human nature. Click through to find out what the most disturbing aspects of being human are.