I explained that even though it may appear to be the case, take a passuk like זאת תורת האדם - this is the Torah of man for example, it is not really true at all. In fact, Adam does not mean man, or at least it doesn't refer to the same element as the word Ish, (איש) man. We can see this from the Talmud in which it explains that a man is not called אדם - Adam unless he is married. From this we can see that a single man is an איש and a woman an אישה (Isha) and only an איש and אישה united constitute the word אדם, Man as in Mankind.
From this we can understand that a husband and a wife are both always performing actions for the whole. When one is learning Torah (either one) the couple is involved in Torah learning. When one is praying, both are involved. When one is preparing for Shabbath, both are involved.
There is no way, shape, form, or reason to try and break this union into its two constituent halves. There is no mitzwah that affects only one half of the whole.
This isn't an apologetic attempt to excuse one spouse or the other from learning Torah or anything else, it is just the opposite. One of the reasons why performing a mitzwah is so powerful is because its effects are hidden from us in this world. (שכר מצוה בהאי עלמא ליכא - there is no reward for a mitzwah in this world because the reward couldn't fit into this world, it is too great!) If we were aware of the awesome divine light that is revealed with each little berachah, we would never get to perform a second mitzwah, we would be blissing out on the first one indefinitely. It is only because the results of our actions are hidden to us that we may stand in the presence of the holy Shechinah (without any awareness of it at all) and continue to exist.
Just as an individual needs to awaken themselves to the true value, import, and effect of his or her mitzwoth, a couple needs to come to terms with the awesome reality that some of the mitzwoth that fall on them to perform can only be accomplished through their spouse.
For the simplest explanation think of it this way, there are mitzwoth that only apply to certain parts of the body, but don't think that a mitzwah taking place locally in one part of the body means that the rest of the person hasn't fulfilled their obligation.
Don't think for a moment that just because we only see the tefillin on the left arm doesn't mean the right arm isn't wearing tefillin.