Stages 3 and 4 of non-rapid eye movement sleep (NREM sleep) are considered deep sleep. Stage 3 is characterized by an increase in amplitude and a reduction of wave frequency. During stage 4 sleep, delta activity is recorded. Stage 1 is the transition from wakefulness to sleep. The EEG shows low brain wave activity. In stage 2, EEG activity is increased, with the appearance of spikes called K complexes.

Sleep has two states: one with no rapid eye movement (NREM or synchronized sleep, which involves four stages) and one with rapid eye movements (REM or dreaming sleep). NREM sleep comprises approximately 75% of the sleep cycle. During NREM sleep, respiration becomes slower and more regular as transition from wakefulness to sleep occurs. During stage 4, or deep sleep, delta activity is recorded on the EEG.

During rapid eye movement sleep (REM sleep), dreaming can occur. Blood flow to the brain is increased and breathing is more irregular. Penille erections may occur. The transition from wakefuness to sleep occurs during non-rapid eye movement sleep (NREM sleep). 

In rapid eye movement (REM) sleep, an electroencephalogram (EEG) shows low brain activity and muscle paralysis normally occurs. During non-rapid eye movement sleep (NREM), stage 1 eye movements are slow. EEG activity increases during NREM stage 2. Eye movement ceases during NREM stage 3. Delta wave activity occurs on EEG readings during NREM stage 4. NREM stages 3 and 4 are considered deep sleep.

During non-rapid eye movement (NREM)sleep, when the transition from wakefulness to sleep occurs, the pulse becomes slower and more regular. During rapid eye movement sleep (REM sleep), dreams occur, blood flow to the brain increases, breathing is more irregular, metabolic rate increases, and muscle paralysis occurs.

The reticular formation is a set of nuclei located in the brainstem that control an individual's level of alertness through its three columns: the raphe nuclei (helps synthesize serotonin for mood control), magnocellular red nucleus (aids in motor coordination), and parvoreticular cellular nucleus (helps breathing control—specifically exhalation).

The substantia nigra is a group of dopaminergic neurons located in the basal ganglia that synthesize the majority of the dopamine in the brain. The pons relay signals to the cerebellum from lower brain centers, and deals with sleep, reflexes, taste, facial expressions, facial sensation, and posture. It is located above the medulla oblongata, which houses the olivary nuclei that form the reticular formation. The frontal lobe allows for control of attention, tasks associated with short-term memory, planning, and motivation. It is comprised mainly of dopamine-sensitive neurons, which allows for selection of relevant information from the thalamus. Last, the lateral geniculate nucleus is a thalamic relay center for the visual system. It receives sensory information from the retina via the optic nerve and relays it posteriorly to the occipital lobe.

Piaget identified four stages of cognitive development: sensorimotor, pre-operational, concrete operational, and formal operational. Each stage is correlated with a series of essential developmental milestones, such as language acquisition and ability to perform simple mathematical calculations. The sensorimotor stage extends from birth to approximately age two, when the child first begins to speak. The pre-operational stage extends from age two to age seven, encompassing the development of imaginative rather than logical or concrete capabilities. The concrete operational stage takes place between ages seven and eleven, during which the child develops logical processing. The formal operational stage extends from age eleven to late teens (15-20) and is defined by the development of higher level thought, such as deductive reasoning, hypothetical thinking, and problem-solving skills.

For this question, we are looking for an answer choice between ages seven and eleven.

Each stage reflects a dialectical struggle between two tendencies, resolution of each conflict results in healthy personality and the acquisition of basic virtues.

The first stage occurs during infancy, and its basic conflict is Trust vs. Mistrust. At this stage, the child develops a sense of trust when caregivers provide consistent and reliable care and affection. This is akin to the formation of secure attachment as described by attachment theory.

The second stage in Erikson’s model occurs during early childhood. During this stage, the child must resolve the conflict of Autonomy vs. Shame and Doubt. Children discover their independence using different skills and abilities (e.g. potty training, learning to tie their own shoes, etc.). Success leads to feelings of autonomy, while failure results in feelings of shame and doubt.

The third stage occurs during the preschool years; the conflict to be resolved is Initiative vs. Guilt. Children try to assert control over their environment and begin to feel a sense of purpose when they succeed. If the child experiences disapproval as a result of their attempts, a sense of guilt is instilled.

The fourth stage in Erikson’s model deals with the conflict of Industry vs. Inferiority. Children are in the midst of coping with new academic and social demands. Success leads to a sense of competence, while failure results in feelings of inferiority.

The use of abstract reasoning and logic emerges during the formal operational stage. Adolescents who reach this fourth stage of intellectual development are able to logically use symbols related to abstract concepts, such as algebra and science.

While intriguing, the other choices are incorrect. The key feature of the preoperational stage is egocentrism. During this stage, children are able to think about things symbolically. Their language becomes more mature and they develop memory and imagination; however, their thinking is based on intuition and still not completely logical (i.e. they cannot yet grasp more complex concepts such as cause and effect or comparisons). At the concrete operational stage, children’s thinking becomes less egocentric and they are increasingly aware of external events. Children develop operational thinking, but still can’t tackle a problem with several variables in a systematic way. The sensorimotor stage occurs during the first two years of life. Infants are constantly experimenting with objects, using their senses to familiarize themselves with the world, such as by putting things in their mouths, and learning about the world through trial and error. Last, the assimilation-accommodation stage is not one of Piaget's developmental stages.

Morality is a set of standards of conduct that is specific to the social group one is embedded in. Socialization is the process by which one person becomes a member of a group, and learning the moral standards of the group is important to retaining group membership. This means that morality cannot develop in isolation, since it is a group-level concept. Morality also does not develop through genetics; although genetics may play a role in a person’s ability to behave morally, the particular moral standards a person holds are learned from the social group they are embedded in. Last, compliance is defined as going along with what others in a group think is right, but it does not imply that the person who is compliant actually agrees with the actions of the group.