Does the head follow the heart in matters of truth?

[Angrboda]

And from the second Wikipedia link, a paragraph which serves as a good response:

A study that investigated the effect of educating people about unconscious biases on their subsequent self-ratings of susceptibility to bias showed that those who were educated did not exhibit the bias blind spot, in contrast with the control group. This finding provides hope that being informed about unconscious biases such as the introspection illusion may help people to avoid making biased judgments, or at least make them aware that they are biased. Findings from other studies on correction of the bias yielded mixed results. In a later review of the introspection illusion, Pronin suggests that the distinction is that studies that merely provide a warning of unconscious biases will not see a correction effect, whereas those that inform about the bias and emphasize its unconscious nature do yield corrections. Thus, knowledge that bias can operate during conscious awareness, is the defining factor in leading people to correct for it.[4]

Of course, I have biases, and of course, I will never be able to control for all of them satisfactorily. But it does make a difference to acknowledge that one has biases and make an effort to address them. Besides, the question was about whether or not it is the "heart" that leads to the formation of beliefs, rather than the "head". One could be utterly biased, and yet still have their "head" do all the "talking".

Yeah, I read that. I have to wonder how persistent the effect of that education is, and whether or not the corrective effect does not wane with time. Regardless, the bulk of people lack such education and are thus not benefiting from any correction effect.

In case I wasn't clear, the heart/head dichotomy was just a metaphor for the dichotomy between non-rational and rational processes of belief formation and development. In that sense, no, one could not be biased and still have the head do all the talking as it is a part of the definition of bias that it is not a rational process/influence.