According to studies done on biological siblings adopted by two different middle class families, it shows as the siblings grow older and live apart from their adoptive families their IQs became more similar (Ceci). The reason for this is because siblings pick similar environments since they share 50 percent of their genes, which shows the impact nurture has on their IQs as well (Ceci). This shows how genetics and nature are more powerful in making siblings alike than similarities in their home environment since they both came from middle class families. In another adoptive study on adoptive and biological siblings, genetics was seen to have accounted for 40 percent of the variances of test scores, which shows the large impact nature has, but it also shows nurture could have accounted for 60 percent of the variances of test scores. (Plomin 114). Recent studies of adoptive, non-biological siblings show that they have no correlation at all in their intelligence levels when they became adults, this shows that since they share no genetics they picked different environments to live in which shaped their intelligences to become completely different (Plomin 115). This explains how shared environments affect intelligence during childhood, but it only affects it during that time (Plomin 115). In conclusion, adoptive children studies help prove that nature is more influential than …show more content…
There was a study conducted on 985 babies that had a low birthweight, and they all shared having a very difficult first three years of their lives (Gregoire). They all took a test at three years old testing their intelligence, and took it again at ages five and eight (Gregoire). It was discovered that the environmental obstacles they went through only temporarily boosted intelligence (Gregoire). Their gains in intelligence were not permanent, this is called the "fadeout" effect (Gregoire). Although, some might argue nurture is more influential in cases like when the babies were more or less intelligent because environmental factors made them have a low birthweight, these spikes or downfalls in intelligence are only temporary, and genetics essentially take over as they grow older. This data also shows that high intelligence at one age doesn 't mean the child will have high intelligence during later stages of their life, because it may “fadeout” if certain environmental needs disappear, like the babies when they no longer were fighting to stay alive because their body weight became normal for their age (Gregoire). Nature is seen to be more influential by evidence concluded from low birthweight baby