IQ Score

• IQ ranges from zero to over 130, with 50 percent of scores falling between 90 and 110. The mean, or average intelligence quotient, is 100. Under 70 is considered mentally retarded, while over 130 is considered very superior.
  
  

Genetic or Environmental

• Correlations indicate that a large percentage of intelligence is genetic, while environmental factors can aid in fostering and encouraging that intelligence. Brain efficiency provided by biological factors creates the potential for high intelligence, whereas a given environment can either help or hinder a person in reaching that potential.
  
  

Difficulties

• IQ tests are criticized for being inaccurate and biased. It is impossible to have a completely unbiased test -- even the materials used to give the examination are biased towards those who are familiar with them. Certain types of questions will be naturally easier to answer for certain segments of the population. Additionally, two people may be able to answer the same question differently with rational answers.