Scientific studies based on average results do have some validity, but what these studies are telling us is not as much as many people think. It is not that the scientific study is necessarily junk science, but a lot of the interpretation of what the results mean is poor critical thinking.
Mark is quite right that the curve can be very important in scientific studies. The shape of the curve can be very important in telling us what the results really mean.
I personally find a lot of the research involving human cognition is very badly done. Human cognition is a complex system and not an area of science where narrow focused studies will tell us much. It needs to be analyzed with many different areas being studied simultaneously.
In my opinion, there is so much poor science in the study of human cognition, it is throwing people off the good science. It is very politically driven with the nurture side being more wishful thinking than good science. In some ways it would be great if we were all born with the same brain and we all had the potential to be good at whatever we worked hard at. Science is about discovering the truth and we have to keep what we want the answer to be out of the equation.
