A study of 20 pairs of identical twins, separated at birth and raised apart, correlated their scores on a standardized creativity test with several factors. The resulting correlation coefficients were as follows: genetic similarity (r = 0.72), exposure to creative activities (r = 0.45), shared household income (r = 0.31), and parental education level (r = 0.28). Based on these coefficients, which factor has the strongest association with creativity scores?