The correct answer here is homeostasis, a internally balanced state in which our needs, and the drives created by those needs, are satisfied. When one is experiencing needs and drives, one is out of homeostasis.

According to Maslow's hierarchy of needs, the need for esteem is the need to achieve goals for approval and recognition in our community. The need for esteem also includes self-esteem and self-approval. The need for esteem is separated into higher and lower level needs, lower being the need to be approved of by others, higher being self-esteem and approval.

Intrinsic motivation refers to doing something because of an internal reward, such as genuinely finding an activity fun, doing something because “it makes me feel good,” etc. Outside, tangible rewards for doing the activity are not really taken into account when deciding whether or not to do it. Extrinsic motivation refers to doing something because of an external reward, such as earning money so you can buy a new computer, joining an after-school activity to boost your college application, etc. As a result, all of the answers provided refer to extrinsic motivations, except for an interest in the material. Reading about psychology essentially “just for fun” is the only choice that reflects an internal reward for reading the textbook.

Parker's lethargic attitude and unwillingness to participate in school are most indicative of "depression." His personality has not been affected, but more so his mood and his outlook. His lack of energy is not a sign of mania and his intact personality rules out disassociate identity disorder and post traumatic stress disorder. 

Mood-congruent memory is the tendency to recall experiences that are consistent with one's good or bad mood. Thus, if the subject is upset, he is more likely to recall negative memories during which he experienced a similar emotional state.

There are seven "basic" emotions that have been observed in nearly every culture on earth, and are recognizable between cultures even if those cultures have never interacted previously. These fundamental emotions are: joy, sadness, anger, fear, surpise, contempt, and disgust. Confusion is not one of the universal expressions.

The limbic system deals with emotion and memory. The corpus callosum connects the left and right hemispheres of the brain.

Positive psychology is a growing field of psychological research that seeks to grow the empirical data on optimal human functioning and positive emotions (e.g., longitudinal happiness)

Paul Ekman was primarily responsible for identifying many of the possible emotions of the human species and how these emotions were expressed facially. He argued that emotions were universal, though culture produced varying factors on to what extent they could be expressed and what situations/ideas would evoke which emotions. He came to this conclusion by studying emotions across cultures.

Richard Lazarus's theory of appraisal, which departs from a physiological explanation for emotion, posits that emotions are a result of people's subjective experience of an event. This theory is exemplified by the old tale of many different people looking at an elephant: each of these people will focus on different aspects of this elephant, like its ears, trunk, feet, etc. Likewise, someone's emotional experience of a busy road depends on his or her interpretation. Many might fear the busy road. Others accept it and feel content. Others focus on the sun outside and feel joy.