Noob question - moving audio clips

Hi,
Sorry for the noob question - I'm sure this is something obvious I'm missing here. 
 
I'm moving an audio clip on the same track, just moving it, so its' adjacent to an audio clip earlier in the song.  I'm doing this by using the smart tool 'move' - and simply dragging and dropping the clip where I want it. 
 
Sometimes when doing this, when dropping the clip into its' desired place, the earlier clip seems to automatically move a bit earlier, retaining the empty space that existed between the two clips?  Is this due to snap to grid settings?
 
Thanks
Russ
 

If that doesn't work change your paste preferences in "Preferences->Customisation->Editing->What to do with existing material" to "blend old and new" I would guess you have "Slide over to make room" selected instead.