CONFIRMATION BIAS, EISEGESIS, CHERRYPICKING, ECHO CHAMBER, OSTRICH EFFECT, BELIEF PERSEVERANCE, BACKFIRE EFFECT, BELIEF CONSERVATISM, SEMMELWEIS REFLEX, and SELECTIVE PERCEPTION
CONFIRMATION BIAS is the tendency to search for, interprete, favour, or recall information that confirms one's preexisting beliefs. It might be because the belief performs a certain function in the life of the person holding it (for instance, the belief in a deity may make one cope better in adversity) or because the person doesn't want to be seen as stupid. So in a desparate attempt to justify the belief, they focus only things that appear to confirm that belief. It's like working from the answer backwards. Normally the proof is supposed to determine the belief but in confirmation bias, the belief determines the proof.
If one wants to be intellectually lazy or insincere, there's nothing that can't be interpreted one way or the other. If a man thinks his wife is unfaithful, every male name in her phone contacts is a proof. If you believe "All men are scum", every story of a useless man is a proof. If you believe in the afterlife, every story of someone who supposedly dies, goes to heaven or hell, and returns is a proof. If you believe an old woman in your village is a witch and you travel home for festivities, she's in trouble. If she frowns, it's a sign that she's a witch. If she smiles, ah, you think "That's exactly how witches smile." If she doesn't greet you, it confirms your belief. If she greets you, it's another proof.
I once dated a lady (she might be reading this right now). One day we walked in a bush footpath and ran our faces into cobwebs. She started speaking in tongues because she believed it was a proof of the presence of a witchcraft network in the area (like you have GSM network signals in your area) and we might have contacted a demonic attack. She was a devoted Mountain of Fire member who had read almost all Olukoya's books. She simply interpreted the data to suit her belief. A Buharist would rather interprete fuel scarcity as the proof of the efficacy of Buhari's anti-corruption fight (something like "the cabal are creating artificial fuel scarcity because corruption is only fighting back").
Sometimes it has to do with recall. When people are asked to remember events, they might only remember the parts that confirm their belief. For instance, because someone believes that her father was a wicked man, all her childhood memories of him will confirm that belief whereas she might be wrong about the poor man. Unknown to her, her belief has wiped out the memories of all the good things the man ever did for her.
EISEGESIS is when people insert their own beliefs into the interpretation of a text, usually the holy books. Even when the verse says something else, you interpret it to say what you want it to say. While exegesis is the objective interpretation of the book, eisegesis is the subjective interpretation - a confirmation bias by the interpreter. It's done to derive personal belief comfort or manipulate people for selfish reasons. Research has shown that this is a common practice. This is why the same verses have been interpreted differently over time.
CHERRYPICKING (picking cherries and discarding the other fruits) is when you select the data that confirm your own belief but discard those that don't. For instance, when you believe that all men are scum and you're trying to prove it, you fail to reckon with the stories of all the wonderful men around but instead, you focus on the stories of the men that are truly scum. When you're asked to present evidence that prayer works, you pick the testimonies of the 5 people who were healed by prayers and forget the remaining 32,874 people who died even after praying. The same Bible which was used to perpetrate slavery was later used to condemn it; people simply cherrypicked from the same book in both eras.
To maintain one's belief and protect it from danger, ECHO CHAMBERS may be useful. An echo chamber is a room where you speak and get your voice echoing back to you over and over again. It's a way of reinforcing your belief. It means situating oneself in a place where only one's belief will exist and contrary views will be absent.
It's the reason why some people will prefer to get news from only the sources that confirm their belief. Example: to Donald Trump, Fox News is real news while CNN is fake news. It's the reason why religious groups prevent their members from interacting with outsiders. They also prevent them from reading books or listening to tapes from outside. It's because their leaders don't want them to be exposed to contrary opinions that might make them evaluate their beliefs and perhaps see the folly in the beliefs.
It's the same reason why people block or unfriend those who oppose them on social media; maintaining a friend list of only those who always agree with you is a form of echo chamber. The echo chamber is similar to the OSTRICH EFFECT in which people intentionally avoid any information that contradicts their belief. For instance they avoid gatherings, individuals, books, websites, or any other source that they know might present a view contrary to what makes them happy. The echo chamber is preferring to hear only the things that confirm ones belief while the ostrich effect is avoidance of things one doesn't want to hear (like some people have run away from my wall or even blocked me ).
BELIEF PERSEVERANCE is the phenomenon in which people maintain their beliefs despite contrary evidence. It might take the form of the BACKFIRE EFFECT in which, when presented with contrary evidence, people react by strengthening their belief rather than dropping it. This is common when people have no argument in favour of their opinion. Rather than accept defeat and drop the belief, they revert to the belief for succor. In such a situation, the more you try to show them proofs that their beliefs are wrong, the more they strengthen the beliefs. They see the criticism against their belief as the proof that their belief is right and thus deserves to be strengthened. They might simply scream the belief back at you as a proof.
BELIEF CONSERVATISM is when confronted with contrary proofs, people revise their beliefs but not sufficiently. Some aspects of the belief still remains. For instance, a sick person has now been "convinced" that he should switch from herbal concoctions to orthodox drugs but instead of dropping the concoctions altogether, he still uses them alongside the orthodox drugs. SEMMELWEIS REFLEX is when people reject any evidence against popularly held beliefs. It's how individuals or a whole society refuse to let go of traditions and cultural norms.
SELECTIVE PERCEPTION is a phenomenon where someone's sensory perception has been affected by their preexisting beliefs. While confirmation bias is cognitive, selective perception is perceptual. For instance, because Tunde's boss thinks he's rude, he won't hear or see Tunde whenever Tunde greets him in the morning. That's sense of hearing and sight. Smith thinks Ngozi is a beautiful girl but Matthew is indifferent. Therefore even though they both see her every morning, Smith notices her hairstyle, her dress, and her makeup while Matthew can't notice any of these. That's sense of sight. A man who thinks his wife is a good woman finds her food very delicious but the day he thinks otherwise, the same food stops tasting delicious. Sense of taste. It's because one's senses can be affected by one's preexisting beliefs.
This is how thinking goes wrong. To be a good thinker, you have to watch out for the aforementioned errors.