Vulcans see, as per said by R. Star, in thoughts, emotions and understanding while mind-melting.
They see a thought, and all underlaying layers, the behind it, so to speak.
Even the thought of the most insane would suddenly become understandable, since a mind-melt gives the understanding behind that insanity.
A pure Emotion-based race to name something would be clear to a Vulcan.
Of course, how the Vulcan will come out of the mind-melt, that's something entirely different...
In the case of the emotion based race, he might become overly emotional and be 'corrupted' in this sense... (in the Vulcans point of view)