ahead

Michael Hoey tells us in his Lexical Priming that we come to expect words/phrases to occupy certain positions in clauses and sentences. This is a FACT about a word that we can add to our knowledge of a word. As the top screen shot shows, ahead is most frequently followed by a preposition: the tag IN indicates preposition. The second screen shot shows which are the most frequent prepositions.

The top screen shot also indicates that the corpus has 2,113 occurrences of ahead ending a sentence and 1,041 ending a unit that concludes with a comma.

It woud seem then that we are primed, through multiple exposures, for ahead to be followed either by of, or to appear at the end of a unit of information.

This is how it is used in the stimulus sentence.