objective scales for the delineation of 'good' - the difference between 'pretty' and 'very'

Inquiring minds want to know. Is there any objective scale for the delineation goodness? I mean, in empirical terms, what is the difference between pretty good, and very good?

I know that it is probably a difference in dopamine and the number of neural connections... But, that simply won't cut it for me...

Any ideas? Inquiring minds want to know!