straightforward response
Refers to how a dude's love-pipe behaves if a gal he's with shows him "The Merchandise".
A guy's having a "straightforward response" when in the presence of a naked chick makes perfect sense if you think about it... if the dude's lulu sticks out firmly and is "aimed" at said "au naturel" damsel, it more-readily facilitates his simply stepping forward and "sticking it in".