In Peter Collins' short film, Fly in the Ointment, he narrates yearning for human touch—his wife's caress—while a fly flickers monochromatically in a lidded jar. "I felt her soft finger tracing a line along my back as she whispered loving words to me... I dreamt of being held, touched and loved."

One of Canada's longest-serving prisoners, Collins spent long stretches in solitary confinement since his incarceration in 1984 for first-degree murder. Fly in the Ointment recounts his experience of being confined alone in a six by nine foot cell, deprived of human contact, intimacy, or touch.

For the estimated 80,000 Americans currently held in some form of isolated confinement, the thought of being touched with care by another human being is an impossible dream. But people outside of the prison population—otherwise well-connected, sociable people—can also powerfully long for human touch.

What some psychologists term "skin hunger" (also known as touch hunger) is a need for physical human contact. Although many people sate their skin hunger through sex, skin hunger isn't exactly a sexual need. Satisfying your skin hunger requires you to have meaningful physical contact with another person, and failing to observe your need for human touch can have profound emotional, even physical, consequences.

Scientists began investigating skin hunger shortly after the Second World War. In controversial experiments run by American psychologist Harry Harlow, infant rhesus macaques were separated from their birth mothers and given the option of two inanimate surrogates: one made out of wire and wood, and another covered in cloth. The baby monkeys overwhelmingly favored the embrace of the cloth surrogate, even when the wire mother was the only surrogate that held a bottle of milk.

From this, Harlow deduced infant macaques needed more than nourishment from their mothers to stay alive. He termed it "contact comfort." As a result of Harlow's research, we now know that human beings need touch, particularly in childhood, almost as powerfully as they need basic necessities like food and water.

Researchers have shown that touch can communicate a range of emotions, serving as an important social tool, and even the act of hugging can reduce your levels of the stress hormone cortisol. A study from the Touch Research Institute, part of the University of Miami, found that Parisian teenagers hanging out in McDonald's restaurants (France is deemed a "high contact" culture) overwhelmingly touched each other more than their American peers, and were less likely to exhibit symptoms of aggression.

"Touching each other keeps the peace," explains Dr Tiffany Field of the Touch Research Institute. A pioneer in the field of skin hunger, Field has long advocated for touch to be reintroduced into educational systems, where fears about sexual abuse and possible litigation have led some US schools to implement no-touch policies. "Touch facilitates intimacy, and most people you touch won't respond with aggression."

It's possible to be touch hungry and not even know it—or even to mistake your symptoms for poor mental health. "People who are touch hungry usually present as being depressed individuals," Field says. "They're withdrawn; their voice intonation contour is flat." She adds that people suffering from clinical depression may also often suffer from touch hunger—and this can be seen in an area of the brain called the vagus. "When you massage these people, their depression levels go down and their vagal activity goes up."

Dr. Terry Kupers, a psychologist and author who has spent decades testifying as an expert witness on behalf of those in solitary confinement, has seen the effects of skin hunger firsthand. "Physical contact is a requirement of being human," says Kupers. "There's something healing about it. It [touch] is not just correlated with being human—it is being human."

Kupers is allowed to shake prisoners' hands when examining them in the state of Mississippi, where he often testifies. "When I touch a prisoner at the Mississippi isolation unit, they tell me, 'You're the first person I've touched except for officers putting handcuffs on me. Aside from that, nobody has touched me in all the years I've been in solitary confinement.'"

He describes the psychiatric literature showing that solitary confinement causes lasting mental health problems as "voluminous." As the mental health issues that plague prisoners in solitary confinement are so vast, it's difficult to isolate an absence of touch as a major contributing factor, but neuroscientist Huda Akil identifies a lack of touch—alongside other factors—as potential factors that might lead the brain to rewire itself and cause psychological problems. The testimony of prisoners such Peter Collins and Wikileaks whistleblower Chelsea Manning highlights how an absence of touch exacerbates the experience of solitary confinement: Writing in the Guardian, Chelsea Manning describes it as "'no-touch' torture."

Besides prisoners in solitary confinement, there is another demographic that illustrates the debilitating effects of skin hunger: the elderly. Being extremely lonely can amount to a chronic medical condition, and it's one that is more likely to surface in later life as friends and family members die off. One study found that lonely people aged 50 and over were twice as likely to die as their non-lonely peers. In comments reported in USA Today, psychologist Janice Kiecolt-Glaser argues that the elderly need prolonged physical contact more than younger generations: "The older you are, the more fragile you are physically, so contact becomes increasingly important for good health."

Research shows that people in Western societies overwhelmingly feel lonelier. According to the National Science Foundation's 2014 General Social Study, a quarter of Americans feel they have no one they can talk to about their problems. One study from British relationship charity Relate finds almost ten percent of people have no close friendships at all, and 20 percent of those in relationships rarely feel "loved." Concurrently, we're spending more time online than ever before: British adults average 21.6 hours a week, according to recent statistics.

Conventional wisdom holds that technology is turning us into maladroit loners, even if it should, in theory, make us more connected. If you took a paper and pencil and stencilled the outline of the average person's online presence—like a modern day Vitruvian man—you could sketch out a web of stretching connections, too numerous to count. Millions of fibre optic cables connect us to our social networks: friends, followers, email acquaintances, even lurkers. So why do we feel more isolated than ever before? Could it have something to do with the fact that none of these connections involve human touch?

"The ease with which we communicate now is probably the biggest change of the last twenty years," explains Professor Kory Floyd of the University of Arizona, an expert in the communication of affection in close relationships. "In some instances, it encourages us to be less thoughtful of what we say—but it doesn't have to."

Having studied affection for nearly two decades, however, Floyd believes verbal or written communication is no substitute for physical touch. "There's an immediacy to touch that words don't have. And there are certain health benefits that seem to be more pronounced when affection is expressed through tactile ways."

Like a pair of binoculars flipped the wrong way, the Internet can have the effect of making us closer together or further apart—depending on how you look at it. No movement illustrates this more powerfully than the Free Hugs initiative, which began in June 2004.

Most of us have seen someone at a music festival wandering around with a "Free Hugs" sign before, but few realize one individual—a Sydney resident who goes by the pseudonym Juan Mann—was behind it. Unlike cuddle parties where you'll pay $45 to be spooned by a stranger ineptly concealing his boner, Mann wanted to bring free affection to the masses.

"I started giving out Free Hugs mostly because at the time I had nobody around. No-one hugged me or socialized with me," he explains over email. "Then out of nowhere this young woman came up to me at a party and hugged me. For the first time in months I felt alive. It got me thinking about all the other lonely people out there in the world who might need or want a hug."

A musician by the name of Shimon Moore spotted Mann handing out hugs in a Sydney mall and thought it was a neat idea. He returned to the mall and filmed Mann, eventually using the footage for his band's music video. The video went viral (it currently has 77 million views) and Mann's project became known all over the world, much to his surprise.

"Did I ever expect this? Not in this lifetime or the next," Mann tells me. "I expected to just be that lone quirky guy in one city, in one corner of the world, hugging complete strangers. But to see that there are so many people around the world willing to take a stand for love and humanity is empowering."

As Trump's demagoguery shows, the most popular narratives are the ones simplest to understand. Immigration is the reason you don't have a job; Islamic extremism is because Muslims are terrorists; technology is disconnecting us all from each other. But the Free Hugs movement teaches us that the simplest narratives aren't always correct. If it wasn't for the internet, Mann would just be a loner in a mall with a cheesy sign.