A social scientist observes how individual persons react to the presence or absence of noise. This scientist is most likely a:

The social scientist in this scenario is most likely a psychologist because the study of individual reactions to stimuli, such as noise, falls squarely within the realm of psychology. Psychologists are focused on understanding behavior and mental processes, including how people perceive and respond to their environment. Observing reactions to noise involves exploring sensory perception, emotional responses, and cognitive processes, all integral components of psychological research.

In contrast, geographers typically study spatial relationships and the physical world, political scientists focus on government systems and political behavior, and economists analyze the production, distribution, and consumption of goods and services. While all these fields can intersect with human behavior to some extent, they do not primarily center on individual reactions to environmental stimuli in the way that psychology does.