Condescension And Intelligence

When someone condescends to you, it's literally an indication of a lack of ability on their part. A poor ability to assess the intelligence level of others is quite straightforward, no different than having a poor ability to work out mathematical problems, comprehend language, or work out spatial relationships between objects.

A person who was adept at assessing the intelligence levels of others would not be detected condescending, because the person they were condescending TO would not be aware enough to notice their tone if they were as dim as they had been assessed to be.

Further, the desire alone to assess the intelligence levels of those with whom one is speaking to indicates something about their personality and level of self-esteem. The exchange of information does not require any such assessment; information exchange is completely neutral. The ego that is looking for ways to boost itself seeks to assess the "limitations" of random others. The other common reason one would make a habit of trying to assess the intelligence "limitations" of others would be for conning, trickery, and thievery purposes. 

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