©Arlene Taylor PhD

Gender differences are sometimes grouped rather arbitrarily into three main categories: primary, secondary, and tertiary differences. Some differences aren’t easily relegated to one category, however, or contributing factors are not well understood as yet, if at all.

Primary Differences 

• Genes
• Chromosomes
• Brain function
• External genitalia 
• Reproductive organs
• Bone structure
• Vision / hearing

Secondary Differences

• Facial hair
• Body hair
• Vocal pitch
• Body fat distribution
• Muscle to fat ratio
• Posture
• Style of walk

Tertiary Differences

• Nonverbals 
• Word usage
• Speech styles
• Use of body space
• Expression of emotions
• Grief recovery styles

Here are some additional examples.

  • Males tend to carry books under the arm, females against the chest. Does this represent a primary, secondary, or tertiary difference or is it unrelated?

  • More males are left-handed. Left-handed males tend to be concrete, pictorial, affective, and verbal. They are also more likely to suffer from immune diseases, migraine headaches, and learning disabilities. Fewer females are left-handed. Even when left-handed, however, they tend to use the right cerebral hemisphere less efficiently than do left-handed males.

  • Since women have found their way into space (space travel, that is), studies show that females can survive more tumbling and disorientation in space before showing signs of shock, perhaps due to increased ability of their muscles to handle chemical imbalances and/or fluid/hormonal changes. Females also survive better in situations such as shipwreck, perhaps due to an increased ability to metabolize fat more efficiently.

  • In terms of perception of equality, males tend to believe that different from women equates with being superior. Males have also been conditioned to believe they have an innate right to rule over other human beings, especially females. Females, on the other hand, are more certain that democracy is the preferred form of government (e.g., there have been very few female absolute dictators in history). Is this related to brain function, socialization, to a combination of both, or to some other factor?

  • Females tend to accept teasing more playfully while males are more likely to respond to teasing with aggression.

  • Females tend to find jokes less funny overall and may chuckle rather than laugh outright. They may be less amused by what they perceive as poor jokes, but tend to rate jokes defined as very funny even higher than their male counterparts do.

  • Males tend to find jokes funnier, generally give most jokes a higher rating, and are more likely to laugh harder at them. Males tend to try harder to be funny and actually may be five times funnier as compared to females (see note regarding types of humor below).

Since a sense of humor is learned, does this represent a primary, secondary, or tertiary difference or is it unrelated? Humor comes in many varieties and both its use and its appreciation is very personal and subjective.

Types of humor that have been identified include:

  • Cognitive humor (fairly sophisticated type including off-the-wall humor such as Larson’s The Far Side cartoons). When you get the joke a sensation comes over you from the sudden mental integration of incongruous ideas, attitudes, or situations.

  • Conative humor (other people’s misfortune including slapstick). It can produce a smug feeling of superiority such as when we laugh at someone slipping on a banana peel.

  • Affective humor (racial, cultural, or so-called smutty jokes).

  • Orectic humor (a combination of conative and affective types of humor). Males and extroverted females are more likely to appreciate orectic humor.

Do these differences represent primary, secondary, or tertiary differences or are they unrelated to these categories? It’s fun to speculate but there is much that is still unknown.

Where it Begins

The human brain begins to develop soon after conception, some say by the fourth day. This is at once exciting and frightening because a woman may not realize she is pregnant until she is several weeks or even months along. Some change their lifestyle once the pregnancy is identified, some don’t. Either way, the little fetal brain is impacted.

The prenatal period is a time of incredible growth for the fetal brain. At peak periods of development new brain cells are generated at the rate of a quarter of a million per second. Hard to believe! It’s the only time during one’s lifespan that the development of the nervous system occurs so quickly. By the time the fetus is ready to make its way into the world, perhaps 100 trillion synaptic connections are already in place. With growth rates like this it’s no wonder that accidents sometimes happen. That is, the developing fetal brain is vulnerable to a variety of nature/nurture events that can potentially change the way in which it develops. Some alterations may not be readily evident at birth, if ever. Others can influence his/her brain for an entire lifetime!

The fetal brain is extremely vulnerable during the first few weeks after it first begins to develop. The cerebellum may be most vulnerable to damage about forty-five days after fertilization, the thinking brain at about eighty-five days. Incidentally, prenatal exposure to alcohol may be a leading cause of mental retardation worldwide. Ionizing radiation has a significant effect on brain development within eight to fifteen weeks after conception. The main sections of brain tissue are visible by the seventh week of gestation.

In adulthood, the brain weighs approximately three pounds and contains upwards of 100 billion neurons, more than 900 billion neuroglia (supporting cells), and 80-250 million fibers in the corpus callosum (it will differ in size and composition depending upon whether it resides in a male brain or a female brain).