The book focuses on six principles used by “compliance professionals” (e.g. salespeople, politicians, executives) that tap into our mental shortcuts to work in their favour. These principles include:

  1. Reciprocity
  2. Commitment/consistency
  3. Social proof
  4. Liking
  5. Authority
  6. Scarcity

The book is filled with hilarious and sometimes shocking examples of these principles that really help cement them in your mind.

In this summary I’ll explain how these principles can be used to influence the behaviour of others plus examples of them in action.


For thousands of years humans have been helping each other with the expectation that one day the favour will be returned. Tribes that were able to work together had a much higher chance of survival. This tendency sticks with us today - when someone else helps us we feel obligated to help them in some way.

People also desperately want to avoid being labelled as a free loader or leech and will go to great lengths to return a favour to pay off their “social debt”.

So how can this be used to your advantage?

If you want someone to help you with something, do a small favour for them first. It increases the chance of them saying yes to your request dramatically.

The favour people return to you can often be much larger than the favour you do for them.

This is one of the reasons free samples/trials are used by so many businesses.

An example from the book explained how a woman let a young teen (who wasn’t insured) drive her car because he helped jump start her car a few weeks before. He ended up crashing and writing off the car.

People will feel compelled to help you out of obligation.

Another way to use the reciprocity principle is the rejection-then-retreat technique:

1. Make a larger request (one that will most likely be turned down)

2. After the person has refused, make a smaller request (what you actually wanted)

3. The person will feel inclined to respond with a concession of their own (complying with your second request)

Your “smaller” request can still be large as long as it is smaller than the first request.

Using a first request that’s too unrealistic will make this strategy backfire.

The trick is to pick a first request big enough to make your smaller request look reasonable.

The reason this strategy works is it looks like you’re doing the person a “favour” by making a smaller request. Which they then feel obliged to return.

If someone tries to use this tactic on you, you can say no to the next favour they ask if you recognise what they’re doing.

Commitment and consistency

Humans have a deep desire to be consistent.

People want to do/be/act what they say they are.

For example a phone survey asked people if they would volunteer to help a charity if they were ever asked to volunteer.

Most people answered “yes” because they didn’t want to be viewed as someone that doesn’t help others.

A charity called these people back a few days later asking if they would volunteer. There was a 700% increase in volunteers using this strategy versus just asking people to volunteer. This shows how intense our desire is to be consistent with what we say or how we view ourselves.

Another use of commitment and consistency is the foot in the door technique: start with a little request in order to gain eventual compliance with related larger requests.

What may happen is a change in how the person feels about getting involved or taking action. Once they’ve agreed to a request their attitude may change as they begin to view themselves as someone who does this sort of thing.

Once their self image is where you want it, it’s much easier to make them comply naturally to a range of your requests that are consistent with their new view of themselves.

When people personally put their commitments on paper: they live up to what they have written down.

Salesmen were able to drastically reduce the number of returns by getting customers to fill out the sales agreement themselves.

A similar strategy is used by companies running giveaways for testimonials. By getting people to write down on record that they love a certain product they are more likely to keep buying it.

Public commitments tend to be lasting commitments.

A tactic commonly used by car salesmen is the lowball strategy. This involves giving someone a small advantage/incentive to carry out an action. Usually this is offering the car at a price cheaper than average. After the decision has been made by the customer but before the bargain is sealed, the original purchase advantage is removed.

This works by building a support system for the commitment to justify the commitment.

Social proof

Social proof is one of the ways we determine what is correct is by finding out what other people think is correct.

We are more likely to imitate someone the more similar they are to us.

For example testimonials from people that look like your target audience are more likely to be effective.

Social proof can sometimes work against us when we need it.

Pluralistic ignorance according to Latané and Darley, is the state “in which each person decides that since nobody is concerned, nothing is wrong. Meanwhile, the danger may be mounting to the point where a single individual, uninfluenced by the seeming calm of others, would react.”

This explains why in crowded places people are less likely to help someone in need unless they see other people helping them.

We seem to assume if a lot of people are doing the same thing they must know something we don’t.

Especially when we are uncertain we will place a huge amount of trust on the collective knowledge of the crowd.

If you’re ever in trouble in a crowd:

1. Identify someone from the crowd - “Excuse me, you with the blue shirt”

2. Tell them exactly what you need help with -  “Please call an ambulance I need help”

When someone knows they’ve been asked to help and know exactly what they need to do they are significantly more likely to assist.


It’s not surprising that we’re more likely to accept requests from people we like.

What’s interesting is how strangers can use this to their advantage to get us to carry out their requests.

Factors that reliably cause liking:

  1. Physical attractiveness - the halo effect where people assume their other characteristics must be good if they look good (this is very powerful and unnoticed by most people).
  2. Similarity - dressing similar to those you would like to influence, having similar interests or background.
  3. Compliments - claiming you “like” the person you’re trying to influence. We have an automatically positive reaction to compliments.
  4. Contact and cooperation - we are more favourable towards the things we’ve been in contact with before (in a positive setting). Sharing common goals can help build camaraderie between people.
  5. Association - being associated with positive news, information or ideas works in your favour e.g. good looking women in sports car ads, athletes/celebrities being shown using a product.
  6. Luncheon technique - people become fonder of the people and things they are experiencing while eating.

The author gives a funny example of how he himself almost fell victim to the power of liking.

A young attractive woman knocked on his door one day asking to complete a survey on entertainment habits of people in the neighborhood.

She began to ask questions around how often he eats at restaurants, goes to the movies or goes clothes shopping. Eager to impress her he started to exaggerate slightly about how often he eats at fine restaurants and is always first to see the latest movies.

After hearing his “impressive” answers she goes onto say that someone like himself who enjoys the finer things in life would benefit greatly from signing up to an entertainment subscription for only $39 per month that gives discounts to regular diners, moviegoers and shoppers.

She was tapping into the halo effect as well as the principle of consistency.

He quickly realised what was happening and explained to her it wouldn’t work on him. She left slightly confused and embarrassed.

To combat the power of “liking” by compliance professionals make sure you pay attention when you begin to feel abnormally positive towards them. This is a sign you need to stay objective when making your decision.


We are trained from birth that obedience to proper authority is right and disobedience is wrong.

The Milgram Shock Experiment found that people continued to administer electric shocks to test subjects (actors) because the authoritative experimenters told them to do so.

Our obedience to authority is automatic with little or no conscious deliberation.

Information from a recognised authority can give us a valuable shortcut for deciding how to act in a situation.

Even just the appearance of authority is enough e.g. an obviously paid actor dressed as a doctor recommending a vitamin supplement.

Three symbols of authority:


  • Individuals with titles such as doctor, professor, judge etc.
  • People automatically abide by the decisions or recommendations from people with these titles as it is easier to trust their judgments rather than make their own


  • It is extremely difficult to resist requests from people wearing authoritative clothes
  • E.g. freshly pressed suit, security guard uniform, doctor's lab coat


  • Owners of prestige luxury cars receive better treatment from other drivers e.g. less likely to be honked at
  • People seen with status items such as jewellery, expensive cars, designer clothes are seen as more authoritative

Demonstrating honesty and knowledge gives you significantly more credibility.

Example: if your website explains why washing machines are extremely overpriced and you suggest cheaper alternatives based on your expert knowledge of the washing machine industry people will trust and even thank you for your help.

How to say no

1.  Is this authority truly an expert?

2. How truthful can we expect the expert to be here?


Opportunities seem more valuable to us when their availability is limited.

“The way to love anything is to realise that it might be lost” - G.K. Chesterton.

People seem to be more motivated by the thought of losing something than gaining something of equal value.

This explains why limited stock or low stock is used by companies so often.

Same applies for selling a product exclusively for a limited window of time.

Customers are often told that unless they buy now they will have to pay more or not be able to buy it at all.

Scarcity works because of a shortcut we use “if something is hard to get it is usually better than something that is easy to get”.

We also lose the choice to do something (buying the product or service) - this is something people inherently hate experiencing.

A study found that young couples who experienced higher levels of parental interference were likely to have a more intense love experience.

When the parental interference weakened the romantic feelings cooled down.

When our freedom to have something is limited, the item becomes less available we experience an increased desire for it.

To make sense of our sudden desire for the item we begin to look for positive qualities to justify it.

This also applies to most things that are banned or made illegal  - we respond with a greater desire and view it more favourably than before the ban.

A prime example of this is restricting/banning sexual content from teenagers. This makes them desire the content more and view it more favourably.

This scarcity principle is also applicable to information not just material things.

A company selling beef was able to sell 6 times more beef when presenting prospects with their usual sales presentation but then informing them that the availability of the product was limited and so was the source of the information (from an “exclusive” contact).

Optimal use of the scarcity principle:

Newly experienced scarcity is much more powerful.

People need to see or experience “abundance” before they can truly feel the effects of scarcity.

If something was always scarce to begin with the scarcity principle doesn’t really work.

If the cause of the scarcity is increased demand this makes the effect even more powerful.

A good example of this is when toilet paper constantly ran out of stock during the early days of COVID-19.

Salespeople often get prospects “sitting on the fence” to purchase quickly by telling them someone is about to buy the item in question.

Remember that scarce things do not taste or feel or sound or ride or work any better because of their limited availability.

How to avoid falling victim to scarcity principle:

  • Notice immediately the second you experience a burst of arousal and desire
  • Ask yourself why do you want the item in consideration?
  • If we want it for the purpose of owning it (not using it) then we should use availability as a gauge on how much to spend
  • If we want it to use it for something we need to remember the item will function equally well whether it is scarce or plentiful

Final thoughts

There’s so much information and complexity in the world. To help us make faster and more accurate decisions we use mental shortcuts. Most of the time these shortcuts are useful and work in our favour.

Influence shows how these shortcuts can be exploited to make us unconsciously comply with requests.

I highly recommend buying this book to get a deeper understanding of the underlying mechanics for each principle as well for the entertaining examples.

“Reading a book isn’t a race—the better the book, the more slowly it should be absorbed.” - Naval Ravikant