If I told you this is the most important article you’ll read this week, you probably wouldn’t believe me. But what if I could say that 75% of your friends agreed? Or if I could pull out the fact that nine out of 10 people of your age, education and income judged the article as relevant to them?* Then, perhaps, you might be more likely to read on.

Many of us are probably aware that salespeople often use psychological tricks to persuade us to buy their products, even if they themselves aren’t aware of how these techniques mess with our mind. We might even like to think we are immune to that sort of manipulation. But the scientific evidence strongly suggests we aren’t. So why are the following hidden sales tricks so effective?

1. Make false comparisons

Take, for starters, the techniques of used car sales. In the name of research, Robert Levine, a professor of social psychology at California State University, Fresno, masqueraded as a salesman at a used car dealership in the early 2000s. As he recounts in his book, The Power of Persuasion: How We’re Bought and Sold, he was worried that he would fail to shift many cars because he wouldn’t be able to remember all the stats about the various models on the lot. Levine quickly learned, however, that plenty of used car salespeople don’t carry this information around in their heads either – to sell a car, they only really needed to memorise a few basic facts that applied to all the models on the lot. What mattered more was showing the cars in a strategic order.

In doing so, the salespeople are making use of the concept of the “base rate fallacy”. When a shopper isn’t aware of the intrinsic value of a product – and the value of used cars can be difficult to judge without some homework – a base rate can be established and then used to emphasise the exceptional value of another product by comparison.

“If a bunch of $200 espresso machines are sitting next to one overpriced $400 espresso machine that does basically the same thing, the $200 machines suddenly look like an obvious good deal,” Levine explains. “This is especially true if you have a skilled salesperson who divulges that the $400 machine isn’t really any better than the others. But the reality is, most of us probably have no idea how much an espresso machine should cost.”

For Levine, however, even an understanding of the psychology behind sales was little help. He says he was hopeless at selling cars, and only managed to shift one over the course of his research.

Perhaps if Levine, a white man in his 50s, had been selling cars exclusively to other middle-aged white males, or to someone also named Robert, Bob or Bobby, he would have taken home more commission, as this next tip suggests…

2. Emphasise social similarities

Research has shown that we are more likely to buy from people whom we trust and like – and we trust and like people who are more like us, even when the characteristics we share are incidental.

Jerry Burger, a professor at Santa Clara University, studies how and when people are most likely to comply with requests that carry a personal cost – such as handing over money. His findings have huge implications for understanding and manipulating selling techniques and buying behaviour. In one series of experiments for example, Burger and his colleagues illustrated how perceived incidental coincidences – like having the same birthday or name as someone else – can change our behaviour towards that person. In the first study, undergraduate students were brought into the lab ostensibly to participate in a study on astrology. Over the course of the study, participants discovered that they had the same birthday as a research assistant posing as another participant. When the research assistant later asked participants to comply with a request – in this case to critique an eight-page paper – participants who thought they shared the same birthday as the assistant were nearly twice as likely to do so.

In the second study, a woman requesting donations for cystic fibrosis research approached female participants who had just completed what they thought was a study on creativity. When the requester wore a nametag indicating they had the same first name as the participant, the participant donated more than twice as much money, on average, as participants approached by a requester who did not share their name. Even more interestingly, if the participants were shown a picture of a girl with cystic fibrosis and told she shared their name, they donated less money than if they were told the girl did not share their name. Apparently it is sharing characteristics with the requester – not with potential beneficiaries – that is most likely to influence our decision to donate money.

3. Create illusion of demand

Another trick is to make it seem like a product is being snapped up by others. In their bestselling book YES!: 50 Scientifically Proven Ways to Be Persuasive, Robert Cialdini, Noah Goldstein and Steve Martin open with an anecdote about Colleen Szot, who they describe as “one of the most successful writers” in infomercials. Szot famously changed the call to action in her infomercials from: “Operators are waiting, please call now!” to: “If operators are busy, please call again.” The subtle change capitalised on something called “social proof” – a principle that says we look to others to inform our own decisions – and led to an increase in sales.

When there is a limited supply of products, showing that other people are buying the product can also emphasise the notion of scarcity, something that we seem very sensitive to. Simply put, we hate missing out on unique opportunities, even when the opportunity is not really unique at all.

In another set of experiments, Burger and his colleague David Caldwell demonstrated that people are more likely to act if they perceive they have a unique opportunity to do so. In one study, for example, participants spent time evaluating products that are typically sold on US college campuses, including an insulated travel mug. Afterwards, with the study apparently over, the researchers mentioned to the participants that the mugs were actually on sale at a reduced price. Some of the participants were simply encouraged to hand over money – but others were told that the mugs were in short supply and that they could only buy one if they drew a qualifying ticket from a hat. In reality, all of the tickets were marked with a symbol that qualified the participants to buy a mug. Sure enough, the ‘lottery’ participants were more likely to offer to buy a mug.

4. Spread benefits, bundle costs


Broadcast in the late 1970s and early 1980s, the Ginsu Knife infomercial (see video, above) was one of the first to use the ‘But wait! There’s more!’ technique, by offering a carving fork, six-in-one kitchen tool, set of steak knives and spiral slicer in addition to the now famous knife.

It’s an example of spreading “gains” over time. If you were told of all the benefits at once, the sell would be less effective.

That’s not the case when it comes to paying though. While gains are best spread out, we prefer to experience our losses all at once. An example of how salespeople exploit this might include a car salesman who tries to sell you something extra for the car at the time of your purchase. They know the best time to persuade you to spend $200 is when you’re already committed to spending significantly more.

5. Induce a feeling of obligation

Studies have also demonstrated that when people receive a favour from someone, they feel obligated to reciprocate in some way – what social scientists refer to as the “norm of reciprocity”.

This feeling can be strong. In a 2006 study, Burger and his colleagues found people are more likely to grant a second request even after they had already reciprocated a favour, at least for a short period.

“Of course, as a heuristic, or rule of thumb, returning favours is a beneficial thing to do,” says Burger. “The problem arises when this rule of thumb is exploited.”

Again, salespeople have learned how to use these behaviours to their advantage.

“A lot of times, salespeople go through extra effort for you and go through all sorts of gestures, because they know it will be really hard for you to later say no. People feel bad taking something for free or somebody’s time and effort without paying them back in some way,” says Burger. “It can be a trick – and the feeling of obligation is very hard to fight.”

6. Think emotional triggers

According to Martin, we are particularly likely to be influenced when we are overwhelmed or uncertain about the right course of action. “Because we don’t have that thinking space, we don’t have the time or resources to ask ourselves if we’re really making the right decision,” he says.

Some research suggests emotions also affect our commercial activity – both as a buyer and seller. A 2004 study, for example, demonstrated that participants were willing to spend 30% more for an item if they had first watched a sad movie clip. (Sellers who had watched the sad clip, meanwhile, were willing to sell the item for 33% less.) Another 2004 study suggests that people who are judged to be particularly emotional have a decreased ability to perceive differences in numbers and assign corresponding values in a rational manner.

As for Levine, his research has given him a newfound appreciation for clever sales techniques, which he says mix art and science. It’s an appreciation mixed with caution though – he says he no longer accepts apparently free gifts.

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*Of course, neither of these statements can be verified… A final tip? Read the small print. 

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The hidden tricks of powerful persuasion