While there are many rational reasons for people to choose to buy a particular product or service, it's often our emotions and personal biases that drive us.
Below is a list of some of the more commonly debated cognitive biases that can affect people's decisions (From "Decision-Making" on Wikipedia):
- Selective search for evidence (a.k.a. Confirmation bias in psychology) (Scott Plous, 1993) - We tend to be willing to gather facts that support certain conclusions but disregard other facts that support different conclusions
- Premature termination of search for evidence - We tend to accept the first alternative that looks like it might work.
- Inertia - Unwillingness to change thought patterns that we have used in the past in the face of new circumstances.
- Selective perception - We actively screen-out information that we do not think is important.
- Wishful thinking or optimism bias - We tend to want to see things in a positive light and this can distort our perception and thinking.
- Choice-supportive bias - occurs when we distort our memories of chosen and rejected options to make the chosen options seem relatively more attractive.
- Recency - We tend to place more attention on more recent information and either ignore or forget more distant information. (See semantic priming.) The opposite effect in the first set of data or other information is termed Primacy effect (Plous, 1993).
- Repetition bias - A willingness to believe what we have been told most often and by the greatest number of different of sources.
- Anchoring and adjustment - Decisions are unduly influenced by initial information that shapes our view of subsequent information.
- Group think - Peer pressure to conform to the opinions held by the group.
- Source credibility bias - We reject something if we have a bias against the person, organization, or group to which the person belongs: We are inclined to accept a statement by someone we like. (See prejudice.)
- Incremental decision making and escalating commitment - We look at a decision as a small step in a process and this tends to perpetuate a series of similar decisions. This can be contrasted with zero-based decision making. (See slippery slope.)
- Role fulfillment (Self Fulfilling Prophecy) - We conform to the decision making expectations that others have of someone in our position.
- Underestimating uncertainty and the illusion of control - We tend to underestimate future uncertainty because we tend to believe we have more control over events than we really do. We believe we have control to minimize potential problems in our decisions.
Reading these, I realise the truth in what Bertrand Russel said: “The fact that an opinion has been widely held is no evidence whatever that it is not utterly absurd”. Decisions and beliefs are hackable.