If I can add...
This is always the danger of publishing videos that are not seen in context (relative to the complete set). I have had many questions on this particular topic in my own inbox because of this video.
This kind of information is covered in the introductory lessons so that it isn't mysterious later on.
I felt the topic was so important... I spent 30 minutes on the various ways to compare images in PI. (I am a bit crazy...)
Concerning the up and down arrows- the information is almost correct...but it only applies to PREVIEWS of a view...and it is CTRL+ <- or -> arrows. In my opinion since previews are vertical by default... the up/down arrows would make more sense.
-adam