The original Lisa and Mac vertical scroll arrows were at the top
and bottom of the vertical scroll bar, and the up-pointing arrow
moved the content down. I ran a user study in the early days of
Lisa development that informed that design.
Most (but not all) study participants expected to position the
mouse near the top of the window to bring the content hidden above
the top of the window into view. One reason was that they were
looking at the top of the window at the time. Another reason was
that they were more likely, as their next action, to select
content in the upper half of the window than in the lower half.
Consequently, we made the upper member of the arrow pair move the
content down. With apologies to computer architects, I’ll call the
majority whose expectations were met by this decision the