I don't have an answer.
I think in the sense it was recently discussed, framed as love vs intellect, it is more of an overarching frame of mind. Humans typically are absorbed into their mind (intellect) by the time they are adults. Indeed, some disciplines teach to "tame the monkey mind." We tend to "run off at the brain," as it were...I know I do and I know people who "think circles" around me. I think (there I go again!) that life in a modern first world civilization almost demands it of us, the only way to get around that would be to be institutionalized...or live the life of a hermit deep in the woods.
I can see where we (often?) try to regain / retain / redevelop that lost sense of overarching love, but once the intellect genie is out of the bottle there is no putting it back (short of brain damage or disease). It seems impossible to "unlearn" anything. We may forget, but knowledge never truly goes away...or so it seems to me.
As for conditional vs unconditional love...hard to call. I think even a child can attach some conditional elements to their giving of love, such as the dog until it bites or the bicycle until it breaks or hurts them. I think some of it may be parental "conditioning" in that children learn more by observing the behavior of their parents more so than the spoken lessons (especially in the early years), so a judgmental parent might foster a greater sense of "condition" attached to love...but that is a guess on my part. Children who receive such judgmental love can tend to grow up being hypercritical of themselves, forever seeking parental approval that never seems to come...which itself can radiate out in their relationships with others.
I think too there is an element to a child's love that is far more forgiving. How often we see kids at each others' throats in one minute playing nicely the next as if nothing ever happened between them? If ever adults could learn that single lesson...
Even after writing all of this, I have to ask what precisely you mean by the term "love?" It can have such a wide range of meanings...