Larry Tesler explains the origins of the Mac's original scrolling behavior
Sunday, Jul 24, 2011
Larry Tesler, one of Macintosh's Founding Fathers, writing on the Interaction Design Association mailing list:
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 "top-endians". The study also examined the question of which way the arrowheads should point. Half the participants thought the upper arrow should point down, the way the content was moving. Half thought it should point up, the direction from which the content was coming. If the latter is surprising to you, consider that a wind blowing air from north to south is called "northerly" in English, and that a standard PRNDL floor shift makes the driver push the stick forward to go into Reverse and backward to go into Drive. If you don't accept those analogies, note that the "elevator" in the scroll bar moves upward when the user presses the up-pointing arrow to scroll content down. Most of the product team wanted the arrows to point the way the content moved, and to point away from each other. The issue was escalated to Trip Hawkins, the VP of Lisa Product Marketing. After hearing the study results, Trip offered to go with the usability study on arrow locations if I'd be willing (which I was) to make the arrows point away from each other because it "looked right".
Be sure to click through to his full post for more insights on the evolution of scrolling, and consider how the decisions the Mac team made so long ago have permeated almost every device on the planet that supports scrolling. Changing that behavior is a huge deal, but one whose time may have come.

For another great story, check out why dialog boxes say "OK".

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