Brain Rules: 12 Principles for Surviving and Thriving at Work, Home, and School

Brain Rule #11 states, “Male and female brains are different” (223). Medina begins by reminding readers that gender biases must not influence interpretation of scientific facts. He also explains that there are differences between sex, which refers to the biology and anatomy of a person, and gender, which is a social construct. The determination of a person’s sex is made by genes. All people can boast an X chromosome, but males pair the X chromosome with a Y chromosome. The X chromosome contains most genes endowed to the person. Because of this, males take on more genetic similarities to their mothers from whom they inherit X chromosomes, while females are more genetically complex.

The anatomy of the brain is highly affected by sex chromosomes. Females have more developed frontal and prefrontal cortexes, the area of the brain that controls decision-making. Conversely, the limbic system, the part of the brain used for emotions, is larger in males. Scientists do not yet know whether the size of a region of the brain correlates with specific behaviors. Medina acknowledges that speaking about sex-specific behaviors is controversial. He warns against using science to subjugate either sex. Brain pathologies do indicate that there is a relationship between sex chromosomes and brain function. Certain mutations in brain development appear to be more common in males. For example, intellectual disability occurs in the X chromosome. Because males only have one X chromosome, they have no other genetic stream to pull from. When males and females experience a traumatic event, different parts of their brain light up. Males are more likely to remember the major events, while females are more likely to remember the emotional details of the event. Medina explains that while there seems to be a biological component, it is impossible for scientists to separate biology from cultural and experiential factors.

Differences between males and females also show up in verbal communication. Females use both hemispheres for speaking and listening, and these hemispheres are connected by a thick cable. Males typically use only one hemisphere with a thinner cable. Young females build relationships by working cooperatively, making direct eye contact, and talking. Young males are more likely to stand side-by-side and engage with one another through physical activity and competition. As these children get older, males give directives and establish hierarchies through commands and physical aggressiveness, while females use verbal communication to establish hierarchies and engage each other in a consensus. This creates communication issues between adult males and females. Amidst highlighting these differences, Medina continues to remind his readers that there are cultural components to these behaviors. He recommends that managers and teachers understand and encourage emotional processing. He also suggests that bringing males and females together for projects can create a fuller team.

Medina’s final brain rule states, “We are powerful and natural explorers” (243). For a long time, philosophers and scientists believed that infants were born with brains like a blank slate. They believed that only experience could form babies into fully-fledged humans. Medina asserts that babies are born with programming that helps them think and learn; the strategies that infants use to learn about the world are the same strategies that adults use. Like scientists, babies test the world around them through observation and experimentation. Babies can imitate—such as when a parent sticks a tongue out—as early as 42 minutes old. By 12 months old, babies can analyze objects and form experiments to see what objects can do. By 18 months, they know that objects that have left their line of sight still exist. Humans and other primates have mirror neurons that reflect a previous experience when observing another creature undergo the same experience. For example, a macaque’s brain lights up in the same neural pattern when picking up a raisin as it does when observing a researcher pick up a raisin.

Humans have the capacity to be lifelong learners. Parts of the adult brain are just as malleable as they were in childhood. Although adults do lose neural pathways, they can also create neurons. In terms of evolution, this is an extremely important part of human survival. As a child, Medina’s interests shifted from dinosaurs to space to Greek mythology. With each new passion, his mother encouraged him to grow his interest. When he announced to his Christian mother than he was an atheist, she bought him a copy of Nietzsche’s Twilight of the Idols. Medina’s mother cultivated his interest in learning. Discovery is an important part of a child’s path to learning. Many children lose their interest in discovery when they begin to associate learning with the acquisition of a reward, such as a grade, rather than knowledge itself.

Medina suggests that the human propensity for discovery means that individuals should seek opportunities to pursue their passions. Companies should provide free time at work to encourage exploration. Schools could utilize discovery by creating space for students to receive on-the-job training. Medina believes that curiosity is the greatest brain rule of the 12.