Baron-Cohen's essentialist argument consists of two chapters in the book; one on evolutionary theory and another on biology. He himself begins the evolutionary theory chapter by noting that he is going to "speculate", so it would be unfair to address this speculation, except to note that his view of prehistory does not seem to have women do gathering or work with tools. The chapter on biology discusses many sex differences in rats, monkeys and humans, but, unfortunately fails to provide any genetic evidence on the two characteristics the book discusses: emphatizing and systemizing. So we must still wait with bated breath for the actual evidence of essentialist sex differences in empathy and systemizing.

Baron-Cohen's last chapter discusses his model in greater detail and speculates about the possibility that an 'extreme female brain' might exist, to correspond to his 'extreme male brain'. He is so concerned about the possible existence of such an extreme female brain that he notes in his conclusions: "Society at present is likely to be biased toward accepting the extreme female brain and stigmatizes the extreme male brain." Slightly odd, I would think, considering that the former type of person is as yet unknown.

The Appendices 2 and 3 contain a test the reader can take to find out his or her type. Unfortunately, many of the questions in the S section are biased. As an example, consider Q7: "If there was a problem with the electrical wiring in my home, I'd be able to fix it myself." What if it was replaced by: "If there was a problem with a broken zipper in my pants, I'd be able to fix it myself?" Would women suddenly look more systemizing? I suspect so. It is also noteworthy that ten years ago I couldn't fix electricity whereas now I can. Has my systemizing talent increased?

I was concerned by the book's assumption that girls and women don't collect things. But they do, witness the groups at any flea market or car booth sale. It will be interesting to see how that could be incorporated into the story. It will also be interesting to see the self-test results after the questions have been corrected.

This kind of stereotyping is degrading to and reflects a poor understanding of autistics and outdated gender stereotypes: to wit, men are superlogical thinking machines who don't feel deep emotional attachments while women are helpless weepy creatures at the mercy of their emotions. And according to the stereotypes of autistics, we're all brilliant mathematical savants who are incapable of experiencing love and affection. I wonder how many autistic people (both male and female) Dr. Baron-Cohen has actually talked to before writing his book, or did he just listen to the statistics of what other experts say? If an autistic child throws a temper tantrum because his or her things are not lined up in the order s/he wants, s/he is feeling genuine emotion. Autism is not about being hyperlogical or emotionless or a mathematical savant, it's simply being on a different wavelength of perceiving the world and sensing things. It is true that autistics will often feel passionate attachment and even love for interests that would seem weird or insignificant to most normal people, but love is love. And for what it's worth, all the other autistics I know both male and female have MUCH more difficulty 'reading' body cues and facial language than any neurotypical male I know.

The book cites a large number of studies of brain physiology and behavior to illustrate the phenomena discussed. This discussion is coupled with strong cautions against stereotyping and a recognition of individual differences. Ironically, the main part of the book--the chapter explicitly develops the thesis of autism as a reflection of an "extreme male" brain--is a bit on the skimpy side, but this is understandable given that previous chapters have alluded to what is to come.

The appendices to this book are a real treasure! Included are photos that serve as a test of one's ability to recognize the emotions expressed by a person's eyes and a number of scales that can be used to measure empathy levels and other relevant characteristics.

This book is very readable and is punctuated with a nice sense of humor.