When the Animal in You (St. Martin's press) was first published in 1995, the challenge was to include a comprehensive personality test in book form. It's relatively easy to do these kinds of tests on a computer, but with more than 45 possible outcomes (the animals), the nine questions generated about 70,000 possible response combinations. The challenge probably explains why no one had attempted to do this before (or since).
Many possible solutions were tried -- including a flip chart that calculated the results -- until hitting on the way to condense the tens of thousands of possible answers into a few dozen pages.
The test is also unique in the way it resolves the results. Every question is assigned a different weight depending on how the other questions are answered. This is because some attributes become more important when combined with other qualities. A big man who is shy and gentle would be quite different from someone who is small and shy. In addition, extreme attributes (very ambitious, or very passive) are weighted exponentially higher.
Millions of people take the test every year, and while it's obviously not meant to be taken too seriously, judging from the thousands of emails we receive it's making people think about themselves and their relationships with animals - which can't be a bad thing.
Author Roy Feinson's three best-selling books, The Animal in You, Animal Attraction (St. Martin's), and The Secret Universe of Names (Overlook) have been translated into ten languages and are focused on the evolutionary underpinnings of human behavior. He is currently working on a book detailing a novel theory of what animals actually see entitled, The Zebra's Stripes.