Cognitive Bias

The unconscious biases that most affect our buying decisions also compound negative or redundant beliefs.  It's difficult to know whether all of these are generally observable effects or whether some have now become diagnosable states, because searching for them online tends to throw up the phrase "X bias, in psychology....".   Some may be seen as quirks of nature while some have roots in society. Still you might find these useful to know, but maybe not to bandy around or pronounce!  See the section on Advertising for more about words to avoid.

Here are 35 that may interest you, taken directly from relevant sections of the Designhacks Codex. Any notes (italics) are mine, please do look them up yourself for the 'proper' descriptions.

Premise: To get things done we tend to complete the things we've invested time and energy in

• Backfire effect - sticking your heels in when wrong, especially when proof is offered.
• Endowment effect - security - valuing your item more than an equal item, just because it's yours. 
• Processing difficulty effect - easy read, easy forget. Focused read, focused memory.
• Pseudocertainty effect - a sure thing feels better than something that 'might' be amazing, no matter the odds
• Disposition effect - doing a good deal now instead of a possible better one later
• Zero-risk bias - being risky or careless about the future for certainty or zero risk, right now
• Unit bias -  satisfaction in finishing what you started, having something completed.
• IKEA effect - putting more value on something because you helped build it
• Loss aversion - letting the pain of potential loss have more influence on your actions than the actual likelihood of loss.
• Generation effect - remembering stuff you thought of for yourself easier than stuff you read, because its yours
• Escalation of commitment - sticking to a course of action because its already cost you so much effort already
• Irrational escalation - as above, even when the continual costs are all signs that you made a massive mistake
• Sunk cost fallacy - as above, but specifically because of the unexpected financial costs - 'paid out too much to go back'

Premise: We imagine things and people we're familiar with or fond of as better

• Out-group homogeneity bias - belief that everyone not in your group is pretty much uninteresting and all the same. Us and them.
• Cross-race effect - finding it easier to recognise faces and expressions on faces that belong to your own racial group.
• In-group bias - favouritism.
• Halo effect - also 'judging a book by its cover' - making a rapid positive impression based on one trait
• Cheerleader effect - also 'group attractiveness effect', seeing your group members as more attractive and likeable
• Positivity effect - heading more and more for the sunny side as you get older
• Not invented here syndrome - organisational tendency to devalue ideas conceived by people outside the group
• Reactive devaluation - picking holes in a good idea because of the person it came from
• Well-travelled road effect - anything you're used to feels like it takes much less time than it really does

Premise: We are drawn to details that confirm our own existing beliefs

• Confirmation bias - cherry picking the information in front of you to confirm your pre-existing beliefs
• Congruence bias - preferring to prove your existing idea rather than looking at other possibilities
• Post-purchase rationalisation - being so determined to love something you paid a lot for, that you ignore any flaws
• Choice-supportive bias - judging a choice you've already made as better and the options as worse, increasing over time
• Selective perception - The ability to only really notice the information that confirms your personal truth
• Observer-expectancy effect - "The act of observation changes that which is observed"
• Expectation bias - hearing or seeing what you fully expect instead of what actually happened
• Ostrich effect - denial of the negative, refusing to see
• Subject validation - making assumptions and jumping to conclusions in the desire for positive, personal connection
• Continued influence effect - when untruths get in your head and influence you even after you've found them out
• Semmelweiss reflex - dismissing new ideas out of hand to continue to support the current model