"Subjective age" describes how an individual "feels" about their age regardless of how old he/she actually is. On the other hand, "functional age," "chronological age," and "physical age" refer to an individual's competence, abilities, and actual age, respectively. 

Fetal alcohol syndrome can occur in children born to mothers who drink alcohol heavily during pregnancy. Symptoms can include distinct facial features, developmental delays, low birth weight, learning disabilities, and hyperactivity. Huntington's disease is a genetic disorder that can include uncontrollable movements, cognitive decline, and emotional problems. Autism spectrum disorder involves problems associated with communication, social interactions, and the presence of stereotyped or obsessive interests and behaviors. Turner syndrome and Klinefelter syndrome are both chromosomal disorders. Turner syndrome is only present in females and involves the presence of one X chromosome. Symptoms include delayed puberty, infertility, intellectual disability, heart and joint problems, and short stature. Klinefelter syndrome is only present in males and involves the addition of an X chromosome. Symptoms can include low testosterone, delayed puberty, infertility, difficulty sustaining attention, and distinct facial features.

The process of accommodation was developed by Jean Piaget during his work on the cognitive development of children. 

Conservation refers to the ability to know that physical properties, like mass and volume, are the same even if the object is in a different form.

In the concrete operational stage, children are able to think logically about the physical world and come to conclusions about physical states. Cody's understanding of the fact that properties such as volume do not change based upon a sample's form indicate concrete operation understanding.

Children during middle childhood (typically between the ages of 7-11) are limited in their cognitive abilities. Although they perform well when problems or questions are presented in concrete terms (i.e., shape, size, color), they perform poorly on tasks that require them to think beyond the concrete, processing at a more abstract level. Claudia would be classified in the concrete operational stage.

The other stages of Piaget's cognitive development theory are outlined below:

Sensorimotor stage (0-2 years): Children learn about their world through their explorations, using sensory and motor functions. 

Preoperational stage (2-6): Children begin to acquire language and represent symbols. 

Formal Operational stage (12+): Adolescents can engage in deductive and inductive reasoning. 

Adolescents think they have an imaginary audience when they believe that everyone is paying attention to them. 

Another limitation of their cognition is personal fable, meaning that they have this unrealistic opionion of themselves. 

Adolescents tend to engage in idealistic thinking, in which they ask "What if" questions, creating a utopia as opposed to a realistic view of the world. 

Propositional thought is actually a cognitive advance during adolescence. They are able to accurately evaluate given verbal statements and rules, without needing to refer to real-world truths or objects. 

The "visual cliff" experiments were designed to test the point in development at which young children acquire depth perception. Infants and toddlers were placed on a glass table with a gradient illusion, and experimenters observed whether they would cross the gradient. If the child crawled across the entire table, they demonstrated a lack of depth perception because they were unable to see (or be scared of) the visual cliff.

The stages of cognitive development, according to Jean Piaget, are the sensorimotor, preoperational, concrete operational, and formal operational stages. During the sensorimotor stage—birth through age two—the infant's knowledge is limited to their sensory perceptions and motor activities. Between the ages of two and six, when a child learns to use language, is the preoperational stage. Between the ages of seven and eleven, the child should gain an understanding of mental operations and begin to think logically. This is the concrete operational stage. From age twelve into adulthood, people will develop the ability to think about abstract concepts, and deductive reasoning will develop during the formal operational stage. 

In contrast to the behaviorist perspective of language acquisition championed by the like of B.F. Skinner, Chomsky argued that, because children can learn the rules of a language from incomplete evidence, that incomplete evidence must be supplemented by an innate linguistic capacity that all human beings are born with.