Well i am not a scientist but if the same survey is conducted in india may be the IQs levels might differ. The reason being the first borns are assigned more responsibility and that responsibility makes the elder siblings trying to forgo opportunities for his younger siblings. If you look up our history many elder siblings have given up their aspirations for their younger brothers and sisters. I am the youngest in my family and my elder brother took up more responsibilities because of which he could not do what he wanted to do but supported me in whatever i wanted to do. So if they say elders have more IQ yes they might have it but dont show it or get over burdened with the responsibilities and the IQs wilts under pressure. Whatever one has to say who has a higher IQ i would say our elders do take up more responsibilites for thier younger siblings unlike in other countries. So the research might bring up different scores but still i think its always good to have some care for you.
