Spymac claims that Apple will be releasing two-button mice in the future:
Two-button mice have been developed at Apple and are scheduled for an introduction during the second half of 2002.
Historically, Apple has only provided one-button mice... due to human interface issues, dating back to the beginning. Written by Jef Raskin:
While I was the first PARC-savvy person at Apple, Larry Tesler was the first PARC employee to join the company. At first he was strongly opposed to the Mac's easier-to-use mouse methods, and I eventually wrote a memo that showed, point by point, that the one-button mouse could do everything that PARCs three-button mouse could do and with the same number or fewer user actions. It was faster and more efficient, and much easier to learn and remember how to use. I had observed that people (including myself) at PARC often made wrong-button errors in using the mouse, which was part of my impetus for doing better.
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