It is said that the first thing we ask of a new-born baby is "Is it a  boy or a girl?" But it might be considered that this is the first thing  we ask ourselves whenever we meet anyone new. Perhaps this is why we  find it so threatening if the cues are uncertain or ambiguous, and even  more so if we find our first assumptions turn out to be incorrect.
Men  are different from women. That would seem to be self-evident. They are  different in aptitude, skill and behaviour, but then, so is every  individual person. So why do we make such a fuss about it? It seems not  unreasonable to suggest that the sexes are different because their  brains are different, but then no two human brains are the same. It is  suggested that our culture is in trouble because many women have been  brought up to believe they should be as good as a man. Well, why not?
We will only touch on these topics briefly. There is enough material  for a dozen books. Suffice it to say that all the studies report on the  way boys and girls are, not how they got to be that way. Or rather how  they were at the time of the study. Commonality across cultures and  species implies some biological basis. The fact that the situation is  changing reflects the power of socialisation.
Other stereotypes, that girls are more sociable, more nurturing, more  compliant and have lower self-esteem, are hard to sustain. One that  definitely seems to have disappeared over the last two decades is that  girls have less motivation to achieve.
There are studies about relative abilities of perception, vision  sound and touch. Certainly, if you watched a carpenter run his fingers  along a planed surface and being able to tell how "true" it was, you  would find it difficult to believe that boys lack tactile sensitivity.
Another is that girls tend to pick up auditory information while boys  do better visually. Several studies suggested that, from school age on,  boys outperformed girls in areas of mathematics involving abstract  concepts of space, relationships and theory. It turned out that these  were gifted pupils. The studies said nothing about the average boy or  girl.
Why are girls more successful at school? Perhaps emphasis on  communication in projects and exams submerges differences. Success at  school nowadays depends on being able to writes essays and examination  papers. If girls are better at verbal communication than boys, then they  are likely to succeed. But, if there are more boys in remedial reading  classes, does it not imply a serious defect in our educational system?
In general, men are taller and heavier than women. In sports, men  tend to outperform women in strength and speed. Women seem to have  greater endurance. In spite of many attempts, sports have never become  completely unisex.
Yet, for example, Ward and Whipp (1)  suggested that running speeds for male and female athletes have improved  steadily through the twentieth century, but women have improved much  more than men. Dyer(2) found the same for  athletics, swimming and cycling. Both predicted that sex differences  might disappear by the middle of the next century. However Seiler and  Sailer(3) point out that, since the date of  their studies, the rate of improvement has much reduced. They suggest a  temporal correlation with the use of performance enhancing drugs, and  their more recent proscription. These have a greater effect on women,  than they do with men, since the latter are already well supplied with  testosterone.
Men, it is said, are generally more aggressive, physically and  verbally, and enjoy taking risks. They play fighting games and enjoy  'dares.' More men than women are convicted for crimes, especially crimes  of violence.
Some say that this is simply a matter of biology, others suggest that  it is a function of the way we organise the sex and gender roles in our  society. In fact, many of the findings, in this area, have turned out  to be unsatisfactory, and often they turn out to be very small  differences with a large degree of overlap.
Biologically, men certainly seem to be the weaker sex. Although one  would expect there to be an equal chance of the fetus being a boy or  girl, it appears that the ratio for boys is about 20 percent higher, yet  only about the same number come to term. This greater tendency for male  fetuses to be aborted carries on, with more boys stillborn and  susceptible to congenital or inherited conditions, such as hemophilia,  cerebral palsy, convulsions, or heart disease. "On average, men  experience heart attacks 10 years earlier than women, and have a better  rate of survival after one year. Symptoms also vary by sex: women  experience shortness of breath, fatigue, and chest pain; most male heart  attacks come on as a sudden, striking pain in the chest."(4) In adulthood, men have greater vulnerability to virus infections and a shorter average lifespan.
In recent years, a great many biological sex differences have been  found throughout the body, including the brain, both in metabolism and  genetic expression. They have for instance, raised worries about  differences in the efficacy and side effects of various drugs.(5)  Another new area of study is the phenomenon of imprinting whereby a given gene from the father could silence or activate a gene from the mother, or vice versa.(6)
However, regardless of the findings that sex differences really do  exist after all, or the pressure to deny them, socially we still expect  women to behave like women and men like men.
The real problem is not that sex differences exist but, in our  everyday intuition of what sexual, or gender, behaviour is appropriate,  our concepts may be too narrow or too rigid. The biological determinism  argument, too often, reinforces this.
While others now say that there is too much biological evidence that  personality development is based on innate precursors to deny the fact  of sexual difference, we cannot ignore the effect of learning. For a  start, the idea that we are the helpless products of our heredity takes  away our free will.
We must not allow those who insist on the difference to blind us to  the similarities and we must not allow the biological stereotypers to  get away with the idea that there is only one kind of man and one kind  of woman. As Sandra Bem puts it: "Fluffy Women and Chesty Men."
As Sayers (7) puts it: "When one  examines these supposedly purely biological accounts of gender roles one  finds that they are rooted in appeal to social, not biological,  considerations. This is true not only of recent biological analyses of  sexual divisions in Society but also of the analogous biological  explanations of these divisions advanced in the nineteenth century. The  similarity between earlier and current versions of the theses that  'biology is woman's destiny' is striking." 
The big issue is the difference in the spatial abilities between men  and women. It seems that men find it much easier to visualise and deal  with spaces, the position of objects, relative heights and dimensions.  In a test involving a three dimensional mechanical apparatus, only a  quarter of the women could perform the task better than men. It is as  well to remember that at least some of the women could perform the task  as well as the men and it isn't recorded if any men were actually worse.
Out of the plethora of papers that had been produced up until 1974,  about differences between boys and girls, Maccoby and Jacklin (8) found only the following main differences:
Males are more aggressive than females.
Though this finding has been challenged, and the definition of  aggression itself questioned, it is a fairly common feature, both of  human cultures and of the more complex species, that male offspring are  more likely to engage in play fighting and adults more likely to fight.  Many workers challenge this, while others assert that it is the primary  indicator of masculinity or femininity.
Females have more verbal ability than males, while males have better visuo-spatial skills.
The distinction seems to appear at about the age of eleven and,  because of the relevance to education, it has received a great deal of  attention. Although girls and boys seem to have the same ability for  computational arithmetic, teenage boys also seem to do better at the  more abstract maths. It might seem that a childhood of social experience  is the primary factor. However, the biological argument suggests that  the hormonal changes of puberty activate previous dormant differences.
Maccoby and Jacklin's 1974 review of the papers on gender and sex  differences is the one most often quoted, and it may be that, more than  thirty years later, another is urgently needed. It has its critics, who  mainly point out that, in a gargantuan task, it was mostly a head count  and didn't take into account the quality of the research reviewed.
Bibliography and Good Reading
- Uncited reference in Fausto Sterling, A., (1992) Myths of Gender, Biological Theories about Women and Men, (p269) New York: Basic Books (bookshelf)
 - Dyer, K.F., (1977) The Trend of the Male and the Female Performance Differential in Athletics, Swimming and Cycling, 1958-1976, Journal of Biosocial Science, 9 (1977): 325-39 in Rose.S, Lewontin.R.C, Kamin.L.J, (1990) Not In Our Genes: Biology, Idealogy and Human Nature. (p138) Harmondsworth: Penguin Books. (bookshelf)
 - Seiler, S., Sailer, S., (1997) The Gender Gap: Elite Women Are Running Further Behind, Sportscience News May-June.
 - Kreeger, K.Y., (2002) Yes, Biologically Speaking, Sex Does Matter, The Scientist 16[1]:35, Jan. 7, 2002 (http://www.the-scientist.com/)
 - Kreeger, K.Y., (2002) The Inequality of Drug Metabolism, The Scientist 16[6]:29, Mar. 18, 2002 (http://www.the-scientist.com)
 - Kreeger, K.Y., (2002) X and Y Chromosomes Concern More Than Reproduction, The Scientist 16[3]:25, Feb. 4, 2002, (http://www.the-scientist.com)
 - Sayers. J. (1982) Biological Politics, London: Tavistock.
 - Maccoby. E.E, Jacklin. C.N, (1974) The Psychology of Sex Differences, Stanford: Stanford University Press (as reported in various commentaries).
 
Citation
Bland, J., (2003) About Gender: Differences
http://www.gender.org.uk/about/00_diffs.htm