Debates about the relationship between birth order and intelligence remain controversial. Birth order is considered a person's ranking by age among his or her siblings. Numerous researchers have studied this topic to find out whether firstborns generally have higher IQ scores than their siblings. Some scientists conclude that birth order strongly influences intelligence; however, others object, arguing that birth order has no effect on intelligence. In this article, my study addresses the effects of birth order on intelligence. Research on birth order effects first began in the late 19th century. Several researchers have stated that the relationship between birth order and intelligence is significant. In 1973, Lillian Belmont and Francis Marolla conducted a study to test the intelligence of nineteen-year-old Dutch men. The results of their study show that a higher birth order is associated with higher intelligence, meaning that standardized test scores decrease as their standing among siblings decreases. Furthermore, there was a constant "intelligence gradient" along birth order. In the fall of 1996, three researchers from the University of British Columbia and the Ohio State University at Mansfield conducted four studies on differences between groups of people. So that the participants were not influenced by previous birth order research, they were not informed in advance that the result would be published or used in any textbook. Their first experiment asked participants to write down the birth order of their siblings, including themselves. Then, they had to evaluate the sibling who had the best academic performance. The findings "are consistent with previous evidence that...... half of the paper ...... and Power of Birth Order - TIME." Breaking News, Analysis, Politics, Blogs, News Photos, Videos, Tech Reviews - TIME.com. October 17, 2007. Web. April 10, 2011. Carey, Benedict. “Study Says Older Children Have Higher IQs” The New York Times, June 21, 2007. Web. April 10, 2011., Delroy L. Paulhus and Chen David. “Effects of Birth Order on Personality and Outcomes within Families.” Cleveland, Edwin Van Den Oord and David C. Rowe. "Resolving the birth order, family size, and intelligence debate." Joseph and MacCallum C. Robert. "Birth order has no effect on intelligence: A response to and extension of previous findings".. 2011.