In motivation theory, for a thirsty person who drinks water, the act of drinking primarily serves to reduce which internal state?

Introduction / Context:
Psychology uses the concept of drives to explain certain motivated behaviors. For example, hunger and thirst are classic drives that push an organism to seek food and water. This question asks which internal state is reduced when a thirsty person drinks water, according to drive reduction theory.

Given Data / Assumptions:
- The person is thirsty, indicating a physiological need for water.
- Drinking water satisfies that need.
- Several terms are listed: instinct, set point, basal metabolic rate, and drive.

Concept / Approach:
Drive reduction theory suggests that physiological needs create an internal state of tension, called a drive, which motivates an organism to act in ways that reduce the tension. Thirst is a drive resulting from water imbalance in the body. When the person drinks water, the need is satisfied, and the drive is reduced. Instinct refers to inborn, relatively fixed patterns of behavior and is not simply reduced by one act. The set point is the regulated value, such as body temperature or fluid level, and basal metabolic rate refers to energy expenditure at rest, not the immediate motivation to drink.

Step-by-Step Solution:
Step 1: Identify thirst as a classic example of a physiological drive in motivational psychology. Step 2: Recall that a drive is an internal state of arousal or tension that pushes an organism to seek need satisfaction. Step 3: Understand that drinking water directly addresses the underlying physiological need, reducing the drive. Step 4: Compare this with instinct, set point, and basal metabolic rate, which are different concepts. Step 5: Choose drive as the specific state reduced by drinking water in a thirsty person.

Verification / Alternative check:
Textbooks describing drive reduction theory often use hunger and thirst as examples: deprivation creates a drive, and eating or drinking reduces that drive, leading to a state of homeostasis. The term drive fits the description of a temporary motivational state, while instinct and set point refer to other aspects of behavior and regulation.

Why Other Options Are Wrong:
Option A: Instinct refers to inborn behavioral patterns shared by a species; while thirst related behavior may have instinctive elements, the theory focuses specifically on drives when discussing reduction.
Option B: The set point is the ideal physiological value that the body tries to maintain; drinking water helps restore the set point but does not reduce the set point itself.
Option C: Basal metabolic rate is the rate at which the body uses energy at rest and is not directly reduced by drinking water in the context of thirst.

Common Pitfalls:
Students may confuse the idea of a drive with the underlying physiological need or with simpler concepts like habit. It is helpful to see the sequence: need (for water) leads to a drive (thirst), which leads to behavior (drinking), which restores homeostasis and reduces the drive. Keeping this chain in mind makes it easier to pick the right term in exam questions.

Final Answer:
The correct answer is a drive, an internal state of tension that motivates behavior because drinking water reduces the drive associated with thirst, bringing the body back toward homeostasis.