What theory focuses on how stimuli are detected under different conditions?

Signal detection theory is the correct answer because it specifically addresses how individuals detect stimuli amid varying levels of background noise and differing contextual factors. This theory incorporates elements such as sensitivity to stimuli and the decision-making process an individual goes through when determining whether a stimulus is present or not. It considers both physiological and psychological factors, acknowledging that detection is not merely about the strength of a stimulus but also about the individual's experiences, expectations, and the specific circumstances surrounding the detection task.

While absolute threshold theory does discuss the minimum intensity of a stimulus that can be detected, it does not take into account the influence of external conditions on detection. Behavioral theory generally focuses on observable behavior and the processes of learning through reinforcement and punishment, which doesn't directly address stimulus detection contexts. Gestalt theory emphasizes organizing sensory input into meaningful wholes, but it doesn't specifically deal with the nuances of detecting stimuli under varying conditions.