The purposes of such signalling are:
- to be seen defending the beliefs of the tribe, thus enhancing one's reputation within the tribe
- in the hope of spreading the tribe's beliefs, thus increasing the tribe's power
- to give the signaller an increased sense of confidence that the beliefs are true
- ...thus reducing one's cognitive dissonance and avoiding the tribal stigma of "losing faith" or "betraying [one's] values"
- This reinforcement appears to be effective because of some flaw in human psychology – possibly there is some sort of neurochemical feedback from seeing or hearing your own beliefs affirmed, even if you are the one doing the affirming.
Rational debate carries with it the assumption that both parties are engaged in a mutual search for truth, and (therefore) that if sufficient evidence is presented against any participant's position, they will modify their beliefs to accommodate this new information because people want their beliefs to reflect reality.
Verbal belief signalling, by contrast, is almost completely decoupled from the actual meaning of the words being stated; they are more like a team slogan than an expression of understanding. If you are seen to disagree with the signal, that becomes a signal that you are not a tribe member and may even belong to a rival tribe. If this should happen, any tribal believers witnessing your transgression will tend to consider it vitally important to be seen maintaining their original beliefs (cheering for the right team) in order to remove any possible social taint of this contact with the enemy, and to clarify to all their fellow tribe-members that they have not been tempted to switch sides.