Here in thes verse, the consequence of their not using their brain, is being void of wisdom and any gauidnace. They are merely like dumb driven cattle who can only hear a call or a cry but cannot distinguish between the shads of meanings, or differentiate wrong from right or light from shade! and hence the verse:
``The parable of those who reject faith is as if one goatherd or shepherd who calls the sheep and goats, in order to rescue them from a serious danger. But they hear nothing save a call or a cry. In fact the infidels and rejector of faith are deaf, dumb, blind, and understand nothing, and they will not return to the path of truth and salvation.