Studies show that the IQs of siblings have only a moderate correlation (about 0.47) so it is not unusual for some child to be significantly more intelligent than their siblings. Traits that are defined by a complex combination of genes are less likely to be passed from one generation to the next intact. Hence height, governed by fewer alleles, has high heredity, while intelligence and temperament, governed by more alleles, have a lower heredity.
When the oldest child in a family is highly intelligent, their younger siblings will be greeted with high expectations by teachers when they come to school. Teachers talk in the staff room about their outstanding students and everyone knows within a short time whether the younger siblings show similar intellectual capacity. This expectation is a double-edged sword; it can prompt the teacher to imbue the younger sibling with a greater opportunity to display their capabilities, however, it can also create intimidating pressure on the child.
Sometimes all the children in a family of intelligent parents emerge with high intelligence and go on to achieve at the highest levels, each competing with the others for intellectual supremacy. This was the case in the famous mathematically gifted Bernoulli family. However, another common effect of one highly intelligent child is to drive the siblings in other directions. Like trees extending their limbs horizontally to escape the shadow of the taller trees, those who are less gifted than a highly intelligent sibling, focus on other areas where they can receive parental sunlight. We see this effect in families where several siblings are high achievers, but in significantly different areas. One may succeed in academe, while the other succeeds in business or an artistic endeavor.
On June 24, I responded to the following Quora question,
In this person’s question you can perceive the pain that can come from observing “up close and personal” a gift that has emerged in one or more siblings. Life is unfair and nature operates on the cruel laws of survival of the fittest, but the good news is that there are many roads to a successful and fulfilling lives. People like Helen Keller who went through life without sight or hearing and earned a college degree attest to the resilience of the human spirit.
