Again I disagree. I think you might find that those women you refer to as 'brighter' (by which I assume you mean would get a higher score in an IQ test) are actually intelligent enough to implement a balance in their lives - an important part of which is spending as much quality time with their kids while they still can, whether working or not, in addition to addressing home, family, friends and own self development issues (which may or may not be work related) It would not be solely to pursue a career and higher income/ avoiding home and domestic issues at all costs.
I feel your view point of what makes a woman 'valuable' to herself or others is so narrow and focused on 'working' in paid employment. There are many women who are SAHMs who volunteer their services - are they also dim? Try to see sahms/ p-timers as 'working' for the development of their families and themselves. What is it about 'stay at home' that bugs you so much?
From your survey population I think you would find that there is little correlation between education levels (of mums) and 'choice' of working or not working. Obviously there would be a high correlation between education levels and income levels. Income levels may have some correlation with full-time working mums as you would expect that a top exec woman may be the higher earner in the household - in which instance you may often find that the husband stays home or works fewer hours to be with the children.
An important statistical correlation would be between increases in numbers of children and 'choice' made. You would most likely find that as numbers of children increase (on the condition that there are two earners in the 'family' and/ or choice is an option), the number of mums choosing to work part-time or stay home would increase - leading us to the well-known conclusion that most mum's, given the financial choice, see the value and actually want to spend time looking after their children, knowing full well that they can return to work in the future. Obviously there are exceptions to this.
Sorry to have to get into the boring stats here but you keep referring to this hypothetical survey which does not justify your comments at all.
The issue here, lest we forget, is that part-time work/sahms has been dismissed as a foolish option and you have implied/ stated that those who make that choice are of a lesser intelligence, in general, than those who choose full-time work.
I would like to say that no matter whether full or part time (or sahm), the majority of mums try to do the right thing for their children and should be admired. No judgments should be made by either group.
Very few agree with you on this and MOST disagree - so in your land of surveys (if we went for the same survey population)you would find that support for your opinion would be so little as to make it insignificant in the grand scheme of things - so let's move on.