  The same points apply to comprehension. We can understand sentences  we have never heard before, even when they are spoken in odd or  unexpected situations. And how we react to the utterances of others  is again dependent largely on our state of mind at the time, rather  than any past history of training. There are linguistic conventions  in abundance, to be sure, but as Chomsky rightly pointed out, human  ‘verbal behavior’ is quite disanalogous to a pigeon's  disk-pecking or a rat's maze-running.. Mastery of language is not a  matter of having a bunch of mere behavioral dispositions. Instead, it involves a wealth of pragmatic, semantic and syntactic knowledge.  What we say in a given circumstance, and how we respond to what  others say, is the result of a complex interaction between our  history, our beliefs about our current situation, our desires,  and our knowledge of how our language works. Skinner's first big mistake, then, was in failing to recognize that language mastery  involves knowledge (or, as Chomsky later called it  ‘cognizance’) of linguistic rules and conventions.