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What is the name of bias or fallacy when, often while in argument, someone expects you to know the same things as he does. Usually, you just say "well, how should have I known that. I'm not inside of your mind."

I've searched through wiki's list of cognitive biases, but couldn't find anything.


To clarify what I have in mind: When people disregard the availability of information to the subject they are talking to. Or maybe they do not take into account that the subject might not have given the question in hand as much thought as they have, therefore he might not have arrived at the same conclusions. Or they just forget the fact something might not be so obvious to the subject as it is for them.

(so in my original post I've been influenced by the same bias to a degree)

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2 Answers 2

up vote 5 down vote accepted

If you had asked about cognitive distortions, I probably could've answered straight away about one of those!

I think it might be an illusion of transparency. Your example somewhat aligns to the definition provided by Gilovich, Medvec & Savitsky (1998):

"... we refer to this tendency to overestimate the extent to which others can read one's internal states as the illusion of transparency." (p.332)

However it doesn't necessarily meet the criteria for someone expecting another person to know the same things that they do. The illusion of transparency is rather an exaggeration of transparency rather than an exaggeration of being epistemologically levelled.

It could be a projection bias or an assumed similarity bias - both of which might be relevant to your scenario. Projection bias refers to the tendency to assume that others share one's current emotional states and thoughts (Hsee & Reid, 2006). An assumed similarity bias refers to the bias that others are similar to the self (Srivastava, Guglielmo & Beer, 2010). The response - "well, how should have I known that. I'm not inside of your mind." is a product of those biases being invalidated.

Hopefully, these were the ones you were looking for.


  • Gilovich, T., Savitsky, K. & Medvec, V.H. (1998). The illusion of transparency: biased assessments of others' ability to read one's emotional states. Journal of Personality and Social Psychology, 75(2), 332-346
  • Hsee, C.K., Reid, H. (2006). Decision and experience: why don't we choose what makes us happy? Trends in Cognitive Sciences, 10(1), 31–37
  • Srivastava, S., Guglielmo, S. & Beer, J.S. (2010). Perceiving others’ personalities: Examining the dimensionality, assumed similarity to the self, and stability of perceiver effects. Journal of Personality and Social Psychology, 98(3), 520–534
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Illusion of transparency seems very close (don't know how I missed that), I'll look into it. I've considered projection bias but rejected it since it's more of a defense mechanism of one's own mind against itself if I understand it correctly. I edited the question just to clarify if anyone else needed more info. Thanks for help. –  Dwelle Sep 23 '13 at 17:36


I can't even find the Family Circus comic where the boy is talking on the phone, playing with a yo-yo, and says, "Look what I can do, grandma!"
Update: Huh, I didn't find that comic, but it's still a Family Circus comic that accompanies the topic.
Grandma: "Tell me, Jeffy, what was this fun dream about last night?"
Jeffy: "Don't you remember, Grandma? You were in it with me." (Jeff and Bil Keane, 8-21)

Other examples in the section include a two-years-old showing someone else a picture with the picture facing the child, a three-years-old making themself invisible by blocking their own vision, and a young boy claiming that he has a brother yet also that his brother does not have a brother (Phillips, 1969, p. 61).


  • Myers, D. G. (2007). Infancy and Childhood. In Psychology (8th ed.) (pg. 139-159). New York, NY: Worth Publishers.
  • Phillips, J. L. (1969). Origins of Intellect: Piaget's theory. San Francisco: Freeman. (p. 145)
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