Most people "want to preserve the smooth flow of interaction" and will typically go out of their way to ignore uncomfortable social situations, says Arthur McLuhan, a social psychology professor at York University in Toronto.
"The most common response to any sort of deviance is doing nothing."
The argument migrated to the restaurant's parking lot, where one of the men allegedly struck Albayrak on the head, causing her to collapse. After two weeks in a coma, her parents took Albayrak off life support on Nov. 28.
The case has received worldwide coverage. A petition to award Albayrak Germany's national order of merit posthumously has garnered 100,000 signatures.
"Where other people looked away, Tugce showed exemplary bravery and civil courage and stood up for victims of violence," German President Joachim Gauck wrote in a letter to Albayrak's family.
Few step up
Gauck's sentiment about exemplary bravery is echoed in a recent social experiment conducted in Sweden by an organization called STHLM Panda.
Over the course of two days, the group secretly filmed a scenario in which a male actor pretended to verbally and physically assault his girlfriend in an elevator while another passenger was present.
Of the 53 passengers who witnessed the seemingly real assaults, only one intervened.
VIDEO: Swedish social experiment
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According to Philip Zimbardo, a noted U.S. psychologist currently researching the impulses behind heroism, most people are unwilling to intervene.
"On the bell curve of humanity, villains and heroes are outliers," he said in a 2010 TED Talk to explain his Heroic Imagination Project.
"In between them is the general population — generally passive and different."
Still, while Tugce Albayrak's actions may not be the norm, people have a strong reaction when they perceive injustice, says Emiliana Simon-Thomas, science director at the Greater Good Science Centre at the University of California Berkeley.
"Human beings and our primate predecessors are wired for fairness," says Simon-Thomas. "We do not like things that are unfair and when we come across them, we feel very strongly motivated to address the unfairness in any way that we can."
Even so, a number of psychological factors can constrain us from acting in a case of harassment or violence, leading to what is known as the "bystander effect," says Simon-Thomas.
The bystander effect
The most obvious, she says, is the perception that if you intervene, you yourself could be physically threatened.
You may also decide against action if there is a group around, and no one else has acted.
Simon-Thomas says a person may assume the group "must know that this isn't really a problem, this is some theatrical program, and I'm the fool who's being drawn into it."
To illustrate this point, many psychologists cite the case of Kitty Genovese, a New Yorker who was stabbed to death in the courtyard of her New York apartment complex in 1964. Reports say a number of her neighbours heard the attack in progress and failed to act.
Today there is considerable dispute over whether the incident unfolded the way it's been described, but many social psychologists use it to illustrate the concept of "the diffusion of responsibility" — that is, deciding not to intervene because others around you have failed to act, or a fear that you might look foolish in front of a group.
We may also decide not to act if we believe that doing so would jeopardize our social standing — for example, a high-school student who risks being ostracized for calling out a more popular student for sexual harassment.
The Good Samaritan study
Time is another factor, as evidenced by a landmark study conducted by John Darley and Daniel Batson in 1973.
In the study, a group of students from the Princeton Theological Seminary in New Jersey was asked to fill out a personality questionnaire and told to give a short talk afterwards. Some were instructed to talk about jobs for seminary graduates, while others were told to discuss the biblical parable of the Good Samaritan.
The experiment was orchestrated in such a way that on their way to the talk, the students would encounter a person doubled over in a doorway.
Expecting that time would be a factor in whether the students intervened, the experimenters told some students that they were late for their talk, some that they had just enough time to get there and some that they had a fair amount of free time before their talk.
The results showed that 63 per cent of those who had ample time stopped to help the man, while only 10 per cent of those who were late did so.
The study also looked at how the topic of each student's talk affected their actions. Fifty-three per cent of those giving a talk about the Good Samaritan stopped to help, while only 29 per cent of those talking about seminary careers did so.
The Good Samaritan study showed that personality and religiosity were not as important in determining action as circumstances.
"There's this assumption in psychology that your personality, your personal attributes, are what cause behaviour," says York University's McLuhan.
"But that 1973 study shows that situational factors have a high degree of influence on your behaviour," and that your inclination to act is less a reflection of your character.