AP Psychology Practice Test

The correct answer captures the essence of signal detection theory, which emphasizes that the detection of a stimulus is influenced not only by the strength of the stimulus itself but also by various psychological factors, such as attention, motivation, and expectations. This theory acknowledges that our sensory systems are shaped by both the physical properties of stimuli and the internal states of the observer. For instance, a person's alertness or fatigue can significantly affect their ability to detect faint signals in their environment, illustrating the interplay between psychological states and sensory detection.

The other options do not capture the full scope of the theory. Proposing a universal threshold or focusing solely on the physical aspects overlooks the complexity of human perception. Additionally, suggesting that detection depends solely on the strength of the stimulus ignores the significant role that contextual and individual psychological factors play in how we perceive stimuli.