The definition of intelligence according to the merriam-webster dictionary is the ability to learn or understand or to deal with new or trying situations or the ability to apply knowledge to manipulate one 's environment or to think abstractly as measured by objective criteria like IQ tests. The definition of achievement is an accomplishment, a result gained by effort, a great or heroic deed. Based on the definitions we can infer that intelligence may not necessarily play a role in achievement. An achievement can be to sail around the world while it may not be the most intelligent decision to make.
Some studies have used identical or monozygotic twins and fraternal or dizygotic twins to get a sense of how strongly heredity affects IQ. Because monozygotic twins begin as a single fertilized egg which then separates, they are genetically equivalent human beings. Most twins are raised together by the same parent(s) and in the same home, and so they share similar environments as well as similar genes. Yet even when twins are raised separately (perhaps because they have been adopted and raised by different parents), they typically have similar IQ scores (McDevitt, Ormrod 2007). A variety of toxic substances, or teratogens, in children’s prenatal or early postnatal environment like, alcohol, drugs, radiation, lead-based paint dust affect neurological development and thus also affect children’s later IQ scores (McDevitt, Ormrod2007). So intelligence clearly has a powerful genetic component. But we can also see a number of environmental aids and hindrances: A stimulating environment, parental encouragement, good schooling, specific reasoning skills, continued practice, and so on, certainly help a person become more intelligent. Likewise, there are certain biological factors that are nevertheless environmental: prenatal care, nutrition (especially in early childhood), freedom from disease and
References: Retrieved on October 12, 2011 from http://www.merriam-webster.com/dictionary/intelligence McDevitt, T.M, Ormrod, J.E., Child Development and Education, (Sep 2007), p. 291-296., Merrill, an imprint of Pearson Education Inc. Winner, Ellen and Monica Cooper. “Mute Those Claims: No Evidence (Yet) for a Causal Link between Arts Study and Academic Achievement.” Journal of Aesthetic Education, Vol. 34, No. 3/4, Special Issue: The Arts and Academic Achievement: What the Evidence Shows. (Autumn – Winter, 2000), 11-75. Winner, Ellen and Lois Hetland. “The Arts in Education: Evaluating the Evidence for a Causal Link.” Journal of Aesthetic Education, Vol. 34, No. 3/4, Special Issue: The Arts and Academic Achievement: What the Evidence Shows. (Autumn – Winter, 2000), 3 – 10.