Notes from ‘The Psychology of Persuasion: Influence’


I have just finished reading this book. It is an interesting summary of psychological studies that relate to how people are able to influence each other. The book gives a number of ways that humans are able to control others.

  • The author explains that these methods are important to understand as we need short cuts. We can’t be expected to recognise and analyse all aspects in each person. Instead we must use our stereotypes, and rules of thumb to categorise things according to a few key features.
  • People are more likely to respond positively when asked for a favour if a reason is given. For example, if asking to jump to the front of a queue a request is more likely to be granted if the reason is explained. For example ‘I am in a rush’ or ‘Running late’.

Contrast Principle

  • The contrast principle – this is why when lifting a light object a medium weight object will feel heavy; however if you lift a heavy weight a medium weight will feel light. This can be used in sales, if someone has just paid £400 for a suit, then a £90 sweater will seem low. However if buying a £90 sweater, then a £400 suit, the second purchase will seem excessive.
  • The author reports estate agents showing prospective buyers run down and expensive properties first, these are set ups, this makes the later properties viewed seem more attractive.
  • This was also seen with ‘Billiard Table Sales’, when customer were shown cheaper models first, and then shown more expensive models the average sale was $150; whereas when they were shown the more expensive models first the average sale was $1,000.


  • This rule is essentially ‘we should try to repay, in kind, what another person has provided us’.
  • This was tested by a professor who sent Christmas cards to people who he had never met, or heard of, and the majority returned Christmas cards.

Commitment and Consistency

  • This is our desire to be consistent with what we have already done. Once we have made a choice or taken a stand, we will encounter personal and interpersonal pressures to behave consistently with that commitment.
  • The example given for this was Christmas toy sales. Supply will often be limited of a must have Christmas toy, frequently this is a deliberate ploy by the manufacturer. This will lead parents to have to by a ‘substitute toy’; and then in January/February buy the must have toy now it has come back into stock. This leads to parent’s buying two toys when they might have otherwise only bought one.

Social Proof

  • Usually when other people are doing something it is the right thing to do.
  • This is why bartenders will ‘salt’ their tip jars with a few dollar bills.
  • 95% of people are imitators, and 5% are initiators.
  • When a emergency event was staged and there was only one bystander they received help 85% of the time (help was called), however when there were already lots of people standing around help was called only 31% of the time.




  • We prefer to say yes to the requests of someone we know and like. This is also used by total strangers to get us to comply with their requests.
  • This is frequently used by salesmen who will get ‘referrals’ from friend’s; this will create a personal link between us and the salesman.
Categories: Book Notes