What Actually Influences Buying Decisions

The Six Principles of Influence and How They Apply to Marketing

Reciprocity: why giving before asking transforms response rates

Humans feel obligated to return favours. Give something valuable and recipients feel compelled to give something back. This principle underlies effective content marketing, free trials, and value first sales approaches. The key is genuine generosity rather than obvious manipulation. People recognise and resent calculated giving designed to create obligation.

Cialdini describes an experiment where a researcher gave subjects a small gift, a soft drink, before asking them to buy raffle tickets. Those who received the gift bought significantly more tickets than those who did not. The size of the gift mattered less than the fact it was given. Small genuine gestures create disproportionate reciprocal obligation.

Social proof: when it works and when it backfires

People look to others when uncertain about decisions. If many others are doing something, it must be the right thing to do. This explains why bestseller lists sell more books, why popular restaurants attract more customers, and why testimonials influence purchasing. We assume the crowd knows something we do not.

Social proof backfires when it highlights undesirable behaviour. Telling people that many others fail to pay taxes on time increases non payment rather than decreasing it. Describing how common littering has become encourages more littering. The same principle applies to marketing: emphasising how many people do not use your product inadvertently normalises non purchase.

‍Scarcity and urgency: the line between effective and manipulative

Opportunities seem more valuable when they are less available. Deadlines create action. Limited availability creates desire. This principle is foundational to sales promotion but easily crosses into manipulation. Fake scarcity destroys trust. Artificial urgency erodes credibility. The principle works only when the scarcity is genuine.

Cookie experiments demonstrate scarcity's power. Identical cookies taste better when they come from a nearly empty jar versus a full one. Scarcity increased perceived value even though the actual product was unchanged. The effect is strongest when scarcity is recent, when abundance was recently lost, and when others compete for the scarce resource.

Psycho Logic vs Economic Logic: Why Rational Arguments Fail

Economic logic assumes people maximise utility through rational evaluation of options. This assumption fails constantly in real behaviour. People pay more for products with perceived quality even when objective quality is identical. They reject better deals because the framing feels wrong. They make choices that serve psychological needs rather than economic optimisation.

Rory Sutherland calls this psycho logic, the psychological rationality that governs actual behaviour regardless of what economic rationality would predict. A fifteen pound penguin nightlight attracts more entries than a thousand pound energy prize in a competition (he references around an energy company) because it satisfies psychological needs that pure financial value cannot. Understanding psycho logic reveals marketing opportunities that economic thinking completely misses.

The implications for marketing are profound. Rational arguments about product features often fail not because they are wrong but because they address the wrong question. Customers are not asking whether your product offers the best objective value. They are asking whether it feels right, whether it matches their identity, whether choosing it makes them feel good about themselves.

Removing Friction vs Adding Persuasion

The fifteen pound penguin that beat the thousand pound prize


An energy company ran a prize draw offering free energy for a year worth over one thousand pounds. It received 67,000 entries. A subsequent draw offering a cute penguin nightlight worth fifteen pounds received over 360,000 entries. One customer turned down a two hundred pound refund saying they would rather have the penguin.


Rational analysis cannot explain this preference. Psychological analysis can. The penguin is a gift for a child, serving emotional rather than financial needs. It is tangible and immediate rather than abstract and future. It feels like fun rather than finance. The psycho logical value exceeded the economic value by orders of magnitude.

How uncertainty creates stronger objections than price

Research shows that uncertainty about what happens next creates more friction than price itself. A one percent chance of a nightmarish experience dwarfs a ninety nine percent chance of a five percent gain. This loss aversion means small perceived risks prevent action even when expected value strongly favours acting.

Men ordering cocktails in bars discovered that uncertainty about what glass the drink would arrive in was enough to make them order beer instead. The risk of a drink arriving in a hollowed out pineapple outweighed the benefit of a potentially enjoyable cocktail. Removing uncertainty, simply by showing pictures of drinks in their glasses, solved the problem instantly.

Making the risky feel safe rather than the expensive feel cheap

Most marketing focuses on making expensive things feel cheap through discounts and value arguments. Behavioural science suggests the opposite approach often works better: making risky things feel safe through guarantees, social proof, and friction removal. Price objections are often actually risk objections in disguise.

This explains why money back guarantees increase sales even though few customers actually use them. The guarantee removes risk, making purchase feel safe. The risk reduction changes the psychological calculation more than any discount could.

Applying Behavioural Science Without Losing Trust

The principles of influence can be used ethically or manipulatively. The difference lies in intent and transparency. Ethical application helps customers make decisions that serve their genuine interests. Manipulative application exploits psychological biases to create regrettable purchases.

David Ogilvy made the point simply: the consumer is not a moron, she is your wife. You insult her intelligence if you assume mere slogans and vapid adjectives will persuade her. She wants information that helps her make good decisions. The best marketing treats customers as intelligent people whose psychological needs deserve respect rather than exploitation.

This is commercial wisdom. Manipulative tactics create short term conversion at the cost of long term trust. Customers who feel tricked do not return. They do not recommend. They actively warn others. The businesses that thrive long term are those that use psychological principles to serve customers rather than exploit them.