A pattern of cognitive biases not yet discussed here are the biases due to having a narcissistic parent who seeks validation through the child’s academic achievements.

HPMOR clearly shows these biases: Harry's mother is narcissistic, impressed by education, and not particularly smart, and Harry does not realize how this affects his thinking.

Here is my evidence:

The Sorting Hat says Harry is driven by "the fear of losing your fantasy of greatness, of disappointing the people who believe in you" (Ch. 77). Psychology texts say that this fear is what children of a narcissistic parent usually feel. The child feels perpetually ignored because the narcissistic parent seeks validation from the child's accomplishments but refuses to actually listen to the child, spurring the child to ever greater heights of intellectual achievement. 

The text supports this view: “Always Harry had been encouraged to study whatever caught his attention, bought all the books that caught his fancy...given anything reasonable that he wanted, except, maybe, the slightest shred of respect” and “Petunia wrung her hands. She seemed to be on the verge of tears. "My love, I know I can't win arguments with you, but please, you have to trust me on this … I want my husband to, to listen to his wife who loves him, and trust her just this once - " (Ch. 1) describes a narcissistic, anxiously needy mother, an avoidant father, and a son whose parents provide for his physical needs but neglect his need for respect (ego). “If you conceived of yourself as a Good Parent, you would do it. But take a ten-year-old seriously? Hardly.” (Ch. 1) 

Harry goes Dark when the connection to his family is threatened. For example: "The black rage began to drain away, as it dawned on him that...his family wasn't in danger [of legal separation]" (ch. 5) indicates that Harry went Dark even though no one’s life was threatened. The cost of Harry’s Dark Side is becoming an adult at a young age: Harry says, “Every time I call on it... it uses up my childhood.” (Ch. 91). This is consistent with spending nearly all free time studying (instead of wasting time with friends) to impress Harry’s mother.

Typically, children of narcissistic parents inherit either narcissistic or people-pleasing traits. I predicted that if my theory is correct then Harry would have a narcissistic personality. To test this, I found a list of personality traits that describe a narcissist (by Googling “children of narcissistic parents” and clicking the first link), and compared with Harry’s personality as described in HPMOR. I got a 100% match. Questions and answers are as follows: 

1. Grandiose sense of self-importance? Check. Harry plans to “optimize” the entire Universe, expects to “do something really revolutionary and important” (Ch. 7), and is trying to “hurry up and become God” (Ch. 27).

2. Obsessed with himself? Check. He appears to only care about people who are smarter or more powerful than him -- people who can help him. He also has contempt for most students and their interests (Quidditch, etc.)

3. Goals are selfish? Check. Harry claims to want to save everyone, but he believes the best way to help others is to increase his own power most quickly. I address two possible objections below:

Harry’s involvement in the Azkaban breakout was selfish, because Harry could not risk losing Quirrell’s friendship: “ It was a bond that went beyond anything of debts owed, or even anything of personal liking, that the two of them were alone in the wizarding world” (Ch. 51). This, again, mirrors a child’s relationship with a narcissistic mother: the child cannot risk losing the mother’s protection. Harry also had selfish reasons for hearing Quirrell’s plan: “There was no advantage to be gained from not hearing it. And if it did reveal something wrong with Professor Quirrell, then it was very much to Harry's advantage to know it, even if he had promised not to tell anyone.” (Ch. 49)

Harry’s efforts to save Hermione are also selfish because Harry sees Hermione in the same way he sees his mother -- weak in many ways and bound by emotions and convention, but someone Harry must impress and protect. Harry’s statement that “it’s disrespectful to her, to think someone could only like her in that way” (ch. 91) makes sense because Harry is disgusted by the Oedipal implications. If Harry’s mother was not narcissistic, then Harry would not have worked so hard to impress Hermione and would have been less disgusted by the thought of being sexually attracted to her.

4. Troubles with normal relationships? Check. Harry is playing high-stakes mind games with the people he is closest to (Quirrell, Draco, Hermione, Dumbeldore), which is not normal friend behavior. Harry has contempt for nearly everyone else.

5. Becomes furious if criticized? Check. When Snape mocked Harry in Potions class, Harry tried to destroy Snape’s career. Quirrell explained, “When it looked like you might lose, you unsheathed your claws, heedless of the danger. You escalated, and then you escalated again” (Ch. 19).

6. Has fantasies of unbound success, power, intelligence, etc.? Check. Harry wants to conquer the entire Universe with the power of his intelligence, and has plans for how to fill an eternity, including to “...meet up with everyone else who was born on Old Earth to watch the Sun finally go out…” (Ch. 39).

7. Believes that he is special and should only be around other high-status people? Check. Harry avoids average students when possible, and certainly does not hang out with them for fun. “Note to self: The 75th percentile of Hogwarts students a.k.a. Ravenclaw House is not the world's most exclusive program for gifted children” (Ch. 12). 

Harry’s association with the (presumably non-special) students in his army is not an exception because minimal text is devoted to Harry instructing them, while much text explains how powerful and high-status the students in the army have become. For Harry, it appears that the army is a tool to use and an opportunity to show off, not an opportunity to give back and help friends improve their skills for their own sake.

8. Requires extreme admiration for everything? Check. Harry takes anything less than admiration for his brilliance as an insult, and responds by striving for new levels of intellectual achievement and arrogance, until the others recognize his dominance. “And I bit a math teacher when she wouldn't accept my dominance” (Ch. 20). Quirrell’s lesson on how to lose described how to avoid making powerful enemies, not how to empathize and care for others -- the insatiable need for admiration is merely delayed and repressed, not corrected.

9. Feels entitled - has unreasonable expectations of special treatment? Check. Harry requires subservience from the school administration, and special magic items such as the time-turner. “McGonagall said, "but I do have a very special something else to give you. I see that I have greatly wronged you in my thoughts, Mr. Potter...this is an item which is ordinarily lent only to children who have already shown themselves to be highly responsible” (Ch. 14).

10. Takes advantage of others to further his own need? Check. Harry justifies his actions toward Draco by saying "I only used you in ways that made you stronger. That's what it means to be used by a friend." (Ch. 97)

11. Does not recognize the feelings of others? Check. One example is Harry not realizing how Neville felt about the prank on the train to Hogwarts. Another is Harry’s remarkably clueless question to Hermione, “Er, can I take it from this that you have been through puberty?" (Ch. 87) Harry has not learned empathy yet: “Harry flinched a little himself. Somewhere along the line he needed to pick up the knack of not phrasing things to hit as hard as he possibly could” (Ch. 86). 

12. Envious or believes they are envied? Check. Quirrell said to Harry, “You have everything now that I wanted then. All that I know of human nature says that I should hate you. And yet I do not. It is a very strange thing.” (Ch. 74)

13. Behaves arrogantly? Check. “Minerva's body swayed with the force of that blow, with the sheer raw lese majeste. Even Severus looked shocked.” (Ch. 19) I can’t think offhand of a single instance when Harry is not arrogant. 

Therefore, I conclude that Harry and Harry’s mother are both narcissistic. If you want further reading on this topic, look up "The Drama of the Gifted Child" by Dr. Alice Miller (Google for the .pdf) for a more detailed description of a child’s typical relationship with a narcissistic parent.

I am sharing this because it reveals a pattern of cognitive biases that many people (like me) who enjoyed HPMOR, and their parents, probably have. Specifically, there is a strong bias toward either narcissistic or people-pleasing habits, and a difficulty with recognizing and following one’s own desires (because the Universe, unlike a parent, never tells people what to do). One possible reason for studying science is to defend against a parent’s emotional neediness and refusal to provide ego-validation by building an impenetrable edifice of logical truth. Unfortunately, identifying the parent’s cognitive biases does not stop their criticism. A more pleasant strategy is to recognize the dynamic, mourn the warping of childhood by the controlling parenting, set appropriate boundaries in the future, and draw validation from following one’s own goals instead of an internalized parent’s goals.