All of these things affect the development of a human before they are even born. Children exposed to tobacco, excessive alcohol, and narcotics in utero can be at risk for potential birth defects. The most powerful factor in prenatal development, however, is genetics. A child's genetic predisposition to deformities or childhood illnesses are a huge factor in that child's development.

A dominant pattern of inheritance describes traits that are expressed over other traits. For example, brown eyes are dominant to blue eyes. It only takes one dominant allele for a trait to be expressed. It takes two recessive alleles for a recessive trait to be expressed.

Behavioral genetics examines how genes and environmental factors influence behavior. Behavioral genetics often involves twin studies and focuses on three primary factors. First, they study what is known as additive—or shared—genes associated with the trait being examined. Next, they examine shared environments. Finally, behavioral genetics also examines non-shared environments. These three components help to explain the extent to which the presence of a particular trait is due to genetic or environmental factors.

Environments that are unique to individuals or those that are experienced differently by each sibling will have varying effects on each sibling. Being treated differently by their parents would create different environments and have different impacts on the behavior of siblings in a family. Non-shared experiences can influence many factors of a child's personality and differentiate them from their siblings. Anything that a person experiences uniquely qualifies as a non-shared environment.

Fraternal twins are just like regular siblings and share 50% of their genes; however they are born at the same time. Identical twins share 100% of their genetic composition.

Fetal Alcohol Syndrome (FAS) can have serious physical and cognitive effects. Lower IQ, eyes being far apart, ears being low down, and smaller stature usually characterize this particular disorder.

"Crossing over" occurs in prophase I of meiosis. It involves the swapping of genetic material between homologous chromosomes. This creates genetic variability in individuals. Crossing over is extremely important because without genetic variablity humans would be very vunerable to different diseases or dysfunctions.

Following a Noam Chomsky "nativist" perspective regarding universal grammar, Dr. Lengua thinks people are born with the ability to communicate regardless of their environmental influences. Social interactionist perspective is the opposite view in that individuals learn language and communication through modeling, dialogue, and corrective feedback. Behaviorist and sociocultural are distractors.

Jeffrey Arnett coined the term "emerging adulthood" to describe 18 to 25-year-olds from developed countries who are no longer adolescents, but still lack financial independence from their parents or guardians.

Alfred Binet was a French psychologist, responsible for inventing the first intelligence test. The Binet test was designed to identify French children who were struggling in school. Binet believed that intelligence was not fixed, but that a child could grow into or be pulled to a higher level of intelligence. By taking this test, children who needed help would be given the attention they needed.