Difference of Mental Level:
We are all familiar with the saying “It makes two to make a difference” which means that if one spouse is a PH.D or even a Masters in any subject and the other respective spouse is only senior Cambridge with a GCE then it is far impossible for the couple to get along with each other no matter if it’s a love match, a forced marriage in which one person is sacrificing his/her life for the sake of her/his parents last wish before their death it near to impossible to get the couple get along with each other and make them tolerate each other thinking time will heal their differences.
It is always better to marry a person of the same educational level then this way you seem to relate to each other in a far better way then saying something of east and he/she understands it of west.
But this can backfire also in some cases there have been couples who are highly educated but they behave in such a manner towards their spouse that it eventually becomes difficult for the latter spouse to have a better half of his/her life any longer and the marriage is ended in divorce and again a celibate is born to roam on the streets in search of a better person.