Any guesses as to why this would be so? My guess is that people thought they were reading faster at fewer words per line because there was less effort involved.

Any guesses as to why this would be so? My guess is that people thought they were reading faster at fewer words per line because there was less effort involved. If it were so, I wonder what it should mean for usability? Should you engineer things so that your users are more effective or so that they believe they are more effective?