A researcher studied 20 pairs of identical twins who were separated at birth and raised in different families. The twins’ scores on a standardized creativity test showed the following correlation coefficients with various factors: genetic similarity (r=0.72), shared household income (r=0.31), parental education level (r=0.28), and exposure to creative activities (r=0.45). Based on these correlation coefficients, which factor appears to have the strongest influence on creativity scores?