This scenario demonstrates extrinsic motivation, where behavior is driven by external rewards or consequences rather than internal satisfaction. The student's increased studying behavior is contingent on the promised monetary reward, making it externally motivated. Extrinsic motivation involves engaging in activities to obtain something separate from the activity itself - such as money, grades, praise, or avoiding punishment. While extrinsic motivators can be effective in the short term, research shows they may sometimes undermine intrinsic motivation through the overjustification effect. The Yerkes-Dodson law relates to arousal and performance, not motivation types, and self-determination theory's relatedness need involves social connection, not monetary incentives.

The student's decreased interest in chess after trophies became the main focus illustrates the overjustification effect. This phenomenon occurs when external rewards are introduced for activities that were previously intrinsically motivated, leading to a shift in perceived causation from internal to external sources. Initially, the student played chess for intrinsic reasons (enjoyment, interest, challenge), but when trophies became prominent, the external reward became the salient reason for playing. When external justification becomes the primary perceived cause of behavior, intrinsic motivation can be undermined. This effect demonstrates how external rewards, while sometimes helpful, can backfire by reducing the internal interest and enjoyment that originally motivated the behavior. The student's interest depends increasingly on external validation rather than inherent satisfaction with the activity.

Learning a new language because the process is enjoyable and personally interesting best demonstrates intrinsic motivation. Intrinsic motivation involves engaging in activities for their inherent satisfaction, curiosity, and enjoyment rather than for external rewards or to avoid punishments. The person finds the learning process itself rewarding and engaging. This contrasts with the other examples, which all involve external motivators: reading for money (extrinsic reward), practicing basketball for starting position and recognition (external status and approval), and studying vocabulary to avoid detention and earn extra credit (avoiding punishment and gaining external rewards). Intrinsic motivation tends to lead to deeper learning, greater creativity, and more sustained engagement because the motivation comes from within rather than depending on external factors.

Eating dinner because of unpleasant stomach pangs is best explained by drive-reduction theory. This theory proposes that physiological needs create internal drive states that motivate behavior aimed at reducing the drive and restoring homeostasis. Hunger creates an uncomfortable internal drive (stomach pangs), and eating reduces this drive by restoring physiological balance. Drive-reduction theory is particularly effective at explaining behaviors motivated by basic biological needs like hunger, thirst, and temperature regulation. While arousal theory deals with optimal stimulation levels, esteem needs involve recognition and respect, and intrinsic motivation involves enjoyment independent of deficits. The person's eating behavior is clearly driven by the need to reduce the discomfort of hunger and restore physiological equilibrium.

The baby's sucking reflex is best explained by instinct theory, which describes inborn, biologically prepared behavior patterns that support survival. Reflexes are automatic responses that occur without learning and are present from birth to help infants survive. The sucking reflex is triggered automatically when the lips are touched, facilitating feeding and survival in early life. This represents an inherited, species-typical behavior that doesn't require learning or conscious decision-making. While extrinsic motivation involves external rewards, self-actualization involves personal growth and fulfilling potential, neither of which applies to reflexive infant behavior. The Yerkes-Dodson law describes arousal-performance relationships in complex tasks, not basic survival reflexes. Instinct theory best accounts for these automatic, biologically programmed responses that promote survival.

Seeking a promotion to feel competent and respected directly relates to esteem needs in Maslow's hierarchy. Esteem needs include both self-esteem (feelings of competence, achievement, and confidence) and esteem from others (recognition, respect, and status). This level involves the desire to feel valued, both by oneself and by others, through accomplishment and recognition of one's capabilities. Esteem needs come after physiological, safety, and love/belonging needs are satisfied, but before self-actualization. While love/belonging needs focus on connection and acceptance, esteem needs specifically involve feelings of worth, competence, and recognition. This employee is motivated by the respect and sense of achievement that comes with professional advancement.

Feeling cared for by teammates and connected to a group most directly reflects the relatedness need in self-determination theory. Relatedness involves the psychological need to feel connected to others, to experience a sense of belonging, and to feel that one is cared for and valued by significant others. This need encompasses feelings of closeness, attachment, and social connection. When teammates show care and include someone in the group, it satisfies this fundamental need for social belonging and connection. Relatedness is one of three basic psychological needs (along with autonomy and competence) that support intrinsic motivation and psychological well-being. This need is about emotional bonds and feeling valued as part of a social group, which is exactly what the athlete experiences through teammate support.

The student's positive response to being included at lunch most directly satisfies the relatedness need in self-determination theory. Relatedness involves the psychological need to feel connected to others, to belong, and to experience care and acceptance from significant people in one's environment. When classmates include the new student at lunch, they provide social connection, acceptance, and a sense of belonging that fulfills this fundamental psychological need. This social inclusion helps the student feel valued and connected to the group, which enhances motivation and well-being. Relatedness is one of three basic needs in SDT (along with autonomy and competence) that support intrinsic motivation. The student's increased motivation stems from feeling socially connected and accepted rather than from increased control or mastery.

Anonymous donation that matches personal values demonstrates intrinsic motivation, where behavior is driven by internal satisfaction and alignment with one's beliefs rather than external rewards. Since the giving is anonymous, the person cannot receive external recognition, praise, or social status from the act. Instead, the motivation comes from the internal satisfaction of acting in accordance with personal values and beliefs about helping others. This represents pure intrinsic motivation - behavior that is inherently satisfying and meaningful to the individual. The absence of external recognition or reward makes it clear that the primary motivation is internal. This contrasts with extrinsic motivation (which would involve seeking recognition or praise), safety needs (protection from danger), and arousal-based explanations (optimal stimulation seeking).

The student's persistence in a difficult course because it feels meaningful aligns with the humanistic perspective on motivation. This perspective emphasizes personal growth, self-actualization, and the search for meaning and purpose in life. Humanistic psychology recognizes that people are motivated not just by deficit needs or external rewards, but by growth-oriented goals, values, and the desire to fulfill their potential. When someone continues challenging work because it provides meaning and supports personal development, they demonstrate the humanistic emphasis on intrinsic growth motivation and self-realization. This contrasts with instinct theory (inherited behaviors), drive-reduction (reducing physiological deficits), and purely extrinsic accounts (external rewards only). The humanistic perspective acknowledges the human capacity for meaning-making and self-directed growth.