Hearts Vs. Heads

Our minds are big, and composed of many parts.  When our parts disagree, other folks tend to see some parts of our minds as more their allies than other parts.  And such folks will tend to support their allies by encouraging us to give more weight in our minds to their allied parts.

One big division in our mind seems to be between our “heart” and our “head.”  But oddly, literature seems to contain far more examples of folks being encouraged to follow their hearts than their heads.  Why this difference?  Katja Grace ponders:

My favorite explanation at the moment is that we always do what our hearts tell us, but explain it in terms of abstract fabrications when our hearts’ interests do not align with those we are explaining to. Rationalization is only necessary for bad news. … We dearly want to do whatever our listener would have, but are often forced by sensible considerations to do something else.

OK, but why do we not as often give the reverse excuse, that we cannot do what our listener and head wants, because our heart compels us otherwise?  I suggested:

We usually know more about what their heart wants than what their head wants. So if they were going to lie they could just lie about what their head wants – no need to invoke the heart.

Here’s another heart-over-head theory:

Maybe the heart is stupider than the head, so we’re more often tempted to fool someone by appealing to their heart. Similarly, we’d prefer to negotiate with the less sharp partner in a business partnership.

Bryan tells me that for the thinking vs. feeling, or “agreeableness”, personality type dimension, more agreeable folks trust their head less and cooperate more via positive heart feelings.  Negative heart feelings, such as anger, are described via other personality dimensions.  So does “think with your heart” really just mean “be more agreeable” and so “succumb to my social pressure”?   If so why don’t those negative feelings come as easily to mind?

Are there other plausible theories?