Genre conventions in film openings

In today's lesson we watched various film openings, I found that each different genre has a typical convection , for example Horror films start building tension from the second the film starts where as romance films don't give any clues to early. I learnt that sound plays an extremely important role with film because without sound it is hard to work out what is going on , for example the film opening for  without sound everybody thought it was a fun happy family vacation film but with sound we found it was a spooky  thriller.