Deep thoughts about superficial thoughts
I was fascinated of Gigerenzers research from the first time on I had heard a talk of him in the city of Göttingen. He spoke about heuristics that led to many quick and ugly decisions of human beings because they would not require much brain ressources. Before reading "Simple Heuristics" I was naive enough to doubt that one could fill a whole textbook with these ideas. Then I realized that Gigerenzer and his group have made a terrific job in developping their ideas into various different directions and discussing every aspect of that theory I could image.
Maybe the most important thing that Gigerenzer and coworkers have shown is the possibility that knowledge can be a hindrance: In an experiment they asked German and American students which city was bigger, San Diego or San Antonio. The Germans outperformed the Americans because they could use the heuristics of recognition: They only knew San Diego and knowing a city is positively correlated with its size. I have a degree in statistics and must admit that I have also learned something new about statistics with this book: Gigerenzers simulations show that simple rules like using the best predictor and dichonomize it can outperform the predictions of multiple regressions when data are sparse.
Some consider Gigerenzer as just an evolutionary psychologist, but he is much more than that. For instance, he has extended the famous experiments of Kahnemann and Tversky and found that people decide more rationally (in the traditional sense, not taking cognitive ressources into account) when information is presented adequatly to them.
Everybody who is interested in psychology should know how heuristics work e.g. in decision making. Gigerenzer's research tells us something about how we managed to develop simple rules that often lead to the right decisions. Hence, it adds something very important to our understanding of the very nature of us as human beings.