English: Graph illustrating the relationship between S (selection) and R (response) in an artificial selection experiment. A value for the trait is selected for and compared to the standard mean S = |(value of trait) - (average)|. Upon examining the next generation, the new average is the response to selection R = |(response average) - {initial average}|. Heritability (the extent to which genetic variation contributes to variation in phenotype) can be determined by taking R/s or G/d.