In the preoperational stage (~2-7 years old), a human can speak and understand language, but cannot yet comprehend concrete logic or complex relationships between characteristics of objects. Piaget also characterizes this as a stage of egocentrism.

An instinct is an innate, fixed pattern of behaviors in response to certain stimuli. Instincts do not need to be learned, and are embedded within an organism at birth. An example of an instinct can be observed in baby kangaroos, or joeys. A joey will immediately climb into its mother's pouch upon being born, without any need for learning such behavior.

Object permanence refers to the ability to know an object still exists even though it is out of sight. Although research on the exact age of onset of object permanence is controversial, the preponderance suggests the age of onset to be between 4 and 8 months old, hence the correct answer in this question is 6 months old. All of the other answer choices are much too late in life for object permanence to first develop.

Alcohol consumption of any amount may cause neurons in an unborn, developing child to overshoot their destinations (especially in the brain and spinal cord), while exposure to radiation may cause neurons to stop short of their final destinations. Consumption of alcohol may result in Fetal Alcohol Syndrome. Unborn children exposed to alcohol may, as a result, suffer from an abnormally small head, growth problems, learning and behavioral disabilities, lower intelligence, and birth defects.

Twin studies show that parenting has little effect on a child’s personality. When young, infants are generally referred to as “difficult” or “easy going.”  These biological personality traits are not greatly influenced by external factors, such as parenting. Parenting does however have a significant influence on a child’s morals, religion, and manners, which can be imposed on a child through discipline and/or exposure. Parenting also influences intelligence, but not to the same extent as morality, religion, or mannerism. Rather, intelligence (and anxiety) is an effect of a child’s secure attachment. 

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.  

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. 

According to Piaget, children develop cognitive and social abilities in a series of 4 stages: sensorimotor (birth to 2 years), preoperational (2-7 years), concrete operational (7-11 years), and formal operational (12 years to adulthood). Egocentrism, according to Piagetian theory, refers to a child's belief that other people experience life in the same way that he or she does. Egocentric beliefs and behavior tend to decrease during the concrete operational stage; however, some egocentrism continues into adolescence. 

The word "teratogen" refers to any substance that hinders fetal or embryonic development and can cause permanent harm to the baby. Examples of teratogen-caused harm to the baby include poor bonding, fetal alcohol syndrome, and higher rates of antisocial behavior.

Twin studies measure the impact of a person's genetics on their development of a certain personality trait. Because monozygotic (identical) twins share 100% of their DNA while dizygotic (fraternal) twins share only 50%, the similarities of results from a pair of identical twins can be compared to the similarities between a pair fraternal twins to estimate the heritability of a personality trait. The heritability of personality traits is a central question of the Nature vs. Nurture debate, which revolves around the extent to which genetic or environmental factors influence development.