Intelligence is a complex topic with no single agreed upon definition. IQ tests aim to measure intelligence relative to age peers, with IQ defined as a ratio of mental to chronological age. The Stanford-Binet and WAIS tests are commonly used to assess intelligence through verbal and non-verbal tasks. IQ scores are generally stable over time but can be influenced by environmental factors like poverty, education, gender, and race/ethnicity. While IQ tests attempt to account for cultural biases, differences in scores between racial/ethnic groups may still be impacted by culture and environment.