Pang: Some of the terms for pieces of the user interface changed between Lisa and Macintosh: what the Macintosh called the "scroll bar," the Lisa called the "elevator." Could you say a little about this?
Espinosa: There were tremendous debates about these terms. In Lisa, the colloquial term for the scroll bar was the "elevator," because it went up and down. The thing that you moved up and down was colloquially called "the thumb." We got off on this "metaphors should be consistent" jag. Even though people do not have windows and trash cans on their desktop, the idea of having a thumb in an elevator was a little-- [Pang laughs] So we decided to call those, a little more literally, a scroll bar and a scroll box. You could explain what they were and how they fit together. The elevator metaphor was useful, and the thumb metaphor was useful-- if you're going through a document, you thumb up, and thumb down. It was a Xerox term.
But the clash of metaphors-- People are remarkable at being able to keep a number of metaphoric systems in their head simultaneously. We studied this, some of us more than others. I went up to Berkeley and talked to George Lakoff about this. He was confused as to what I was talking about, he had no idea; I haven't talked to him since. Be was one of my college professors. But Metaphors We Live By, and every book of his that I read is absolutely astonishing. Most of the programmers I work with have Women, Fire, and Dangerous Things on their bookshelf. it's about categorization, and object-oriented programming is all about categorization. Programmers read linguistics; they really, really do. We read Metaphors We Live By, and it both gave us the determination to build things on a metaphoric system, and a little bit of freedom, knowing that people can keep multiple metaphoric systems in mind and mesh them without mixing them. If they're too intertwined, people get very confused.
So we wanted to keep to a small number of metaphoric systems that interrelated, but we didn't want to go as far as-- I think a good example of taking a metaphoric system too far is Microsoft Bob, where you have an entire environment that constrains what software can do to mimic real life in a metaphoric way, and impose artificial constraints to fit the metaphor. I think that's much less successful.