Researchers from the University of Bristol believe that taller children tend to have higher IQ test scores than their shorter peers, The Independent reports. Specifically, their study indicates that there is a connection between the amount of growth hormones in the blood and a child's IQ. According to the news outlet, these hormones help determine how fast youths arrive at their final adult heights.

Their 2005 study looked at about 540 8-year-old children. After these students complete an IQ test, researchers measured the level of insulin growth factor (IGF) in their blood. Doing so indicated that their is a positive correlation between IGF and IQ. In other words, children who had higher levels of IGF tended to have better IQ test scores.

David Gunnell, the leader of the study, said that these results can be explained in many ways. For example, if children are shorter than their peers, they may have had poor fetal and post-natal growth, which is connected to slower neurodevelopment.

Throughout the years, researchers have tested many other variables to see what can affect a child's IQ, including their head size. According to Science Netlinks, Grant Hulburt, a professor at California State University, said that a larger head can predict higher IQ scores to some degree. 

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