You can use the left and right arrow keys to look at your movie one frame at a time.
Thanks Steve, but this does not create a playback that can be understood. I need something more like a consistent playback at quarter or eighth speed; similar to clicking the fast forward button to play at double speed or faster, but in the other (slower) direction. I have used this feature on other applications, but can't find it on Premiere. Can I assume from your answer that this is not possible?
Hold down the Shift key as you tap the L key.