When Rachel Botsman was five years old, her parents discovered that the family’s nanny, who’d come with stellar references, was actually one of London’s biggest drug dealers. They had no idea about her side hustle — right up to the point when she used the family Volvo as the getaway car in a bank robbery.

Though Botsman was too young to fully understand what was happening, “that experience of betrayal and deception had a massive impact on my view of the world,” she says. “How could my parents have trusted a criminal to look after me? How were they conned? How did they get it so wrong?”

Today, Botsman is a lecturer on trust and skepticism at Oxford University and author of the book Who Can You Trust? Perhaps surprisingly — considering she encountered her first major example of deception before kindergarten — Botsman’s answer to the question in her book title is an optimistic one: Trust, she explains, is innate, and a vital part of our day-to-day existence.

“Trust is an elusive concept, and yet we depend on it for our lives to function,” she noted at the start of her 2016 TED Talk. “I trust my children when they say they’re going to turn the lights out at night. I trusted the pilot who flew me here to keep me safe. It’s a word we use a lot, without always thinking about what it really means and how it works in different contexts of our lives.”

But while trust may be a necessary part of life, we’re not always great at knowing how and when to use it — as anyone who’s ever been swindled, cheated, or let down can attest, it’s easy to mistake confidence for competence. (In fact, that’s the root of the term “con,” which entered the vernacular as shorthand for “confidence.”) Untrustworthy people use pure swagger to lure us into believing they can safely handle our money or personal information; they adopt a tone of certainty that convinces us that whatever they’re putting forth is true.

“We often don’t recognize that things that seem too good to be true are, in fact, too good to be true.”

The shortcut to determining whether or not to trust someone, Botsman says, involves making a quick assessment of four traits:

1. Competence: Do they have the skills, knowledge, time, and resources to do a particular task or job? Are they honest about what they can and can’t do?

2. Reliability: Can you depend on them to keep the promises and commitments they make? Are they consistent in the way they behave from one day to the next?

3. Empathy: Do they care about your interests as well as their own? Do they think about how their decisions and actions affect others?

4. Integrity: Do they say what they mean and mean what they say? Do their words align with their actions? Are they honest about their intentions and motives toward others?

The best con artists are tough to identify, Botsman says, because they know how to manipulate the signals that activate our innate sense of trust. Often, they’ve done enough research to gain an intimate understanding of their mark’s vulnerabilities. They may even give you an immediate feeling of familiarity.

“Con artists like Bernie Madoff, Elizabeth Holmes — and my drug-dealing nanny — feed off the trust of others and our self-delusion or propensity for optimism,” Botsman says. “We often don’t recognize that things that seem too good to be true are, in fact, too good to be true.”

Unlike trust, skepticism is a learned behavior — which means you can improve with practice. It may not be your first instinct to mentally measure someone seemingly well-intentioned against a set of questions like the ones Botsman described. But do it enough and eventually it will become second nature to think critically about what you’re hearing.

That also applies beyond face-to-face interactions. To be a more critical consumer of information, it helps to think like a scientist, says neuroscientist Paul Zak, author of The Moral Molecule: How Trust Works. That means adopting the scientific method — formulating a hypothesis, then testing it — in everyday life. A piece of new information is a theory; it’s only after you feel you’ve vetted it appropriately and ruled out the alternatives that you can absorb it as fact.

“A lot of science has a ‘therefore’ problem,” Zak says. “You read a study, and it says, ‘Therefore, these guys concluded X.’ But why can’t [the conclusion] be Y or Z?” It’s easy to fall into the trap of blindly trusting information backed up by “experts” or people who hold certain degrees or have certain areas of expertise. But there are plenty of times when preliminary findings become lodged in the zeitgeist as fact, even when they’re not. A 2017 paper by researchers at the University of Bordeaux tracked the media coverage of more than 150 studies and found that publications are far more likely to cover initial findings — especially those with positive results — and almost never cover subsequent research, even when it contradicts or nullifies the earlier information.

So, while expertise and education can certainly lend someone more credibility, it helps to remember that neither negates the fact that humans are fallible and have their own motivations. A scientist, for example, may understand things you don’t, but that doesn’t mean you’re required to trust their findings.

Still, fallible though they might be, other humans can be a valuable resource when you’re trying to figure out whether or not to trust someone or something new. Botsman points to the power of review apps and websites specifically: “There’s a lot of discussion about how technology has made us more vulnerable to scams, con artists, and fake information,” she says. “But it also has a huge amount of promise to help us make more informed decisions.”

Platforms like UrbanSitter, for instance, use your existing network to connect you with childcare professionals who’ve been vetted by people you actually know. Angie’s List performs background checks on home service providers, and sites like Consumer Reports and Wirecutter independently test and review products to tell you what works and what doesn’t. Offline, you can apply a similar principle, leaning on people or institutions you already trust to help guide you through the process of deciding who else deserves it.

And in situations where you don’t have that context available, it’s especially important to remember one more element of Zak’s “think like a scientist” mantra: You have to be willing to be wrong. Once you’ve decided to take a leap and trust someone, it’s easy to fall victim to confirmation bias, twisting facts to fit the narrative that you’ve made the right choice. Instead, constantly reevaluate and question until your hypothesis proves itself — or doesn’t. Some amount of blind trust will always be necessary just to get through the day, but that doesn’t mean you can’t change your mind.

“Skepticism is a great tool to help us get the information to make smarter trust decisions,” Botsman says. “It can make us question the integrity of a person, company, or thing. Is this person really who they say they are? Is this product or service really what it claims to be? Do they really have my interests at heart? Sometimes, a lack of trust is not the issue; it’s giving our trust away too easily to the wrong people.”