Emotions are a product of evolution designed to signal when humans need or want something or when a certain need or want has been met. Emotions are universal, as they can be observed cross-culturally, though the degree of expression of emotion may vary in different cultures. 

Gherlin is secreted by an empty stomach and tells the brain to switch hunger on. Leptin is secreted by fat cells and tells the brain to switch hunger off. Serotonin is a neurotransmitter associated with feelings of well-being.

Primary drives refer to things a person needs to survive, like thirst and hunger. Secondary drives are determined by social factors, money, pride, and fame are all great examples of secondary, not primary, drives.

The Yerkes-Dodson law is a curve known for its bell shape, relating its independent variable (i.e. arousal) to its dependent variable (i.e. performance). This graph shows that performance peaks at moderate levels of arousal, as high levels of arousal result in stress while low levels of arousal result in boredom. 

Downward social comparisons are defense mechanisms that present when people seek to preserve or defend their self-esteem. These mechanisms come in the form of comparing oneself to others who are worse off—less successful, less happy, or less fortunate.

The affiliation motive is a need to be involved with others. This need is heightened when people feel like celebrating or feel anxious.

Personal satisfaction is an example of intrinsic motivation, since it is driven by internal rewards. 

Kurt Lewin classified conflicts based on whether they posed desirable or undesirable consequences. In an approach-approach conflict, a person is faced with two desirable options. For example, a person must choose between going to one of two restaurants that he enjoys. In an avoidance-avoidance conflict, a person is faced with two undesirable options. For example, a person has to decide between spending his afternoon cleaning or studying for an exam. In an approach-avoidance conflict, a person is faced with one option that has both desirable and undesirable consequences. In the case of this example, Sam is faced with both pros and cons associated with joining the swim team. In a multiple approach-avoidance conflict, there are several conflicts that pose both pros and cons. Last, the term ambivalent is not used in Lewin's classification. 

Intrinsic motivation is defined as motivation to complete a behavior because it is internally satisfying to the person. On the contrary, extrinstic motivation is defined as motivation to complete a behavior to acquire extrinsic rewards (for example, money, food, or elevation of status). 

Maslow's hierarchy of needs ranges from physiological needs (at the bottom of the pyramid) to self-actualization needs (at the top of the pyramid). Self-actualization involves achieving one's unique potential, and is much more spiritually oriented than the lower levels.