The term self-concept is a general term used to refer to how someone thinks about or perceives themselves. It is an important term for both Social Psychology and Humanism.
IQ stands for Intelligence Quotient. It is a score that combines the mental age of a person with his chronological age. For testing purposes, the mental age is determined by a series of standardized test questions, known as the IQ test. It is estimated that well-known scientist Albert Einstein had an IQ of 160 or more.
The test used was the Wechsler-Bellevue (in German). The average IQ is 128, just short of two standard deviations above the mean of 100. None of these men had below average intelligence. I find it difficult to believe that these IQs were overestimated.