What theory of perception proposes that detection of stimuli depends on a variety of factors including, but not limited to, physical intensity of the stimulus, fatigue of the observer, and expectancy?

The signal detection theory  of perception proposes that detection of stimuli depends on a variety of factors including, but not limited to, physical intensity of the stimulus, fatigue of the observer, and expectancy.
This theory holds that the detection and the likelihood to detect some stimulus depends on both the intensity of the stimulus (for example how loud is the music) and the physical and psychological state of the individual (how alert you are).