First born children tend to have a higher IQ than their siblings

Question

Is there any truth to this? Would love to piss off my sister

Answer 1

According to The University of Edinburgh, firstborns have a mental edge over their younger siblings. The article expressed how parents helped to develop the thinking skills of the firstborn more by reading with them or doing crafts. They also noted that mothers took more risks during later pregnancies by smoking more.  

As the eldest daughter but not the eldest sibling, I find that I have areas where I am more intelligent than my older sibling. There is more emotional intelligence, and I am more English/arts smart, while my brother is more math/science smart. When we both took the ACT, with no outside prep classes, I scored higher than him on the first attempt.

https://www.ed.ac.uk/news/2017/first-borns-have-mental-edge-study-shows#:~:text=First%20borns%20score%20higher%20than,tasks%20that%20developed%20thinking%20skills.

Answer 2

According to the University of Edinburgh, firstborns tend to have a higher mental age than their younger siblings. This was found by a study, conducted by observing 5,000 children from pre-birth to age 14. The study found that "First borns score higher than their siblings in IQ tests as early as age one." This can be explained by the birth-order effect, which says that "children born earlier in a family enjoy better wages and more education in later life."

https://www.ed.ac.uk/news/2017/first-borns-have-mental-edge-study-shows

Answer 3

The University of Edinburgh actually conducted a study with results concluding that first borns do have the mental edge. "Our results suggest that broad shifts in parental behaviour are a plausible explanation for the observed birth order differences in education and labour market outcomes."  https://www.ed.ac.uk/news/2017/first-borns-have-mental-edge-study-shows