Robert Cialdini’s book Influence is the classic bestselling text on the subject of persuasion and why people behave the way they do. Because the psychological principles it describes are so useful when it comes to marketing and sales, it’s become one of the most popular business books of all time.
So what are the principles of influence?
1. Automatic behaviour
Certain things trigger an automatic response. For example, the large head/eyes to body ratio of a baby is something we are pre-programmed to respond to and this makes us more caring and protective towards children. Even if it’s an animal, which we have no logical reason to be protective over, we naturally find young animals ‘cute’ and have similar feelings towards them.
Use 1: This automaticity can be taken advantage of in sales. When something is priced highly, we automatically associate the high price with high value. One anecdote tells of a shopkeeper who accidentally marked up a clearance item to 10X its value and actually sold more of it.
Use 2: Also, when we see that the price of an item has been reduced in price we automatically think: ‘I’m saving X… what a good deal’.
As buyers we should be aware when these tactics are being used against us. If you ever wonder why every online product is marketed as $2047 value, reduced to ‘only $67!’, this is why.
2. Reciprocity
When someone at work buys you a Christmas card or gift have you ever been stricken with the very strong feeling that you now have to get them something back. Damn! Reciprocity is a bitch.
Companies have long used free samples to get new customers. Reciprocity is a big part of why that works. Nowadays content creators who blow you away with massive free value rely on this principle to get you donating or buying their products. We feel we owe them something for the great stuff they’ve given us for free. We should give something back, right?
One of the most interesting things about this is that is if you give someone a small gift/favour and then ask for a big one in return, there is a good chance they will still feel obliged, even though it’s a completely lopsided exchange. That’s the power of reciprocity – it’s a very strong rule of human psychology, not to be underestimated.
3. Relativity
I ask you to borrow $1000, you say no. I then ask you to borrow only $100. What do you say? There is a good chance that you say yes the second time.
The second proposal is presented as much smaller and more reasonable relative to the first, so it’s much more likely to be accepted. Because I retreated from my initial position, making a concession, the reciprocity rule also comes into effect, psychologically pressuring you to do the same. Double persuasiveness!
I only wanted $100 the whole time! I have just used a sales tactic on you that Cialdini calls the rejection-then-retreat strategy.
4. Commitment and consistency
When you make a commitment to doing something, or acting in a certain way, you are much more likely to follow through. You are psychologically more committed. You want to act like the person that you have presented yourself to be.
For this reason, Trump gets prospective voters at rally to shout out that they are going to vote in a hall filled with thousands of witnesses. This increases turnout on vote day.
Tony Robbins recommends that dieter’s make their goals public. If you told everyone you knew that you were going to lose weight, don’t you think you’d have a better chance of following through, knowing that if you didn’t you’d look foolish?
Written commitments are even better. Generally, the more effort or ‘investment’ we put into something, the more committed to it we are to follow through. Writing something out takes slightly more effort than saying it, so it’s slightly more likely to stick.
This explains many things such as why we value more that which we have worked hard to achieve, why we tend to undervalue things that we get for free, and why don’t quit bad jobs or bad habits when we should – we have sunk so much investment into them already that we feel committed.
5. Social proof
When something is seen as being popular in the eyes of other people, especially a great many other people, it becomes very desirable.
This is why when someone starts to build up a following, their success snowballs. If Bob has 7 million instagram follower’s he must really be something, right?
You see that something is a best seller, it’s top of the charts. Why? What’s all this buzz around it? It must really be sensational stuff!
Advertiser’s use this all the time to sell to us. One little trick used by unscrupulous marketers is to launch a book on Amazon in an obscure category where it’s very easy to become the number one ranked book. They then claim that their book was ‘number one on Amazon’ and that they’re a ‘bestselling’ author, a claim that can be used to generate more sales by the magic of social proof. Naughty, naughty, but it can work.
This allows a successful businessman to snowball their success by building up a track record. It’s much harder for the little guy staring out who has no social proof. Such people will do well to collaborate with more successful individuals and entities in order to absorb some of their social proof.
6. Liking
We are far more likely to accede to a request if it is from someone we like, indeed we are far more likely to give them our business.
Persuaders use this to their advantage by leveraging other people we like (friends, celebrities) in persuading us.
What are some of the factors that lead to is liking someone?
- Physical attractiveness – there is an automaticity in liking good looking people that operates at a subconscious level where we appraise their genes as being superior and desire to associate with good looking people. Good looking people are proven to do better in court, receiving more compensation and smaller fines, for example. They earn, on average, more throughout their lifetimes. (From my reading on genetics and intelligence I also know that there is a weak positive correlation between good-lookingness and IQ).
- Similarity – we like people who more who dress in a similar way to us, who have similar beliefs, values systems, hobbies and interests. If we are married then we like those who are also married.
- Compliments – they work. In fact, flattery works better on men than women, who are more used to being flattered. A car salesman in the book used to send his clients a card every month saying simply ‘I like you’. This complement cost the salesman a decent amount of money in mailing fees, but obviously he made a positive return on this!
- Contact and cooperation – if you can get someone to think of you as being on the same team (perhaps against someone else) you’re in!
- Association – we like things that we associate with other positive/desirable things. The classic example would be that in a car advert with a hot girl, the hot girl makes the car seem more desirable.
7. Authority
In the famous Milgram experiment, named after the researcher who performed it, subjects had to act as the assistant of a scientist to administer electric shocks to a second participant (who was secretly an actor). The experiment found that the majority of everyday people would administer terribly powerful electric shocks to the second participant even when pleaded and begged not to because the authority (the scientist) had told them to continue.
Most people are very pliable and conditioned to obey authority to a worrying degree. Authority can be conveyed in a number of ways, especially by credentials, titles, trappings (fancy cars etc) or how someone dresses. Con artists will usually dress the part and frequently adopt title such as ‘Doctor’ or ‘Professor’ in order to increase their perceived authority in the eyes of their mark.
8. Scarcity
Scarcity is when something is rare or limited in supply. Everyone has heard of the limited time offer or the phrase ‘while stocks last’. We want what we can’t have. We hate the idea that an opportunity is being deprived us, and feel compulsion to act ‘while we can’.
One man who used to buy and sell used cars would invite multiple prospective buyers to view the car at the same time rather than at different times. When the buyers knew that there was competition for the car, they would be incredibly easy to sell to.
We also want more something that has been banned or censored, automatically perceiving its value to be higher. If you hear that people are trying to ban green hats, you are much more likely to develop a passionate interest in green hats.
If you rail against those trying to ‘shut you down’ that is a sure way to build a following!

























