SIGNAL DETECTION THEORY

The first topic we will cover in this chapter is signal detection theory (SDT). Let's begin by considering an area of psychology closely associated with SDT – psychophysics. The first psychological experiments ever conducted were in psychophysics. Psychophysics describes how physical stimuli, such as light or sound waves, are translated into subjective impressions – what we see and hear. For example, we know that the wavelength of light determines the color we perceive.

But our subjective impressions do not map onto physical stimuli in a one-to-one fashion. There are several variables that can affect our subjective impression. Take the physical environment. Imagine that you are listening to another person at a cocktail party, and the party grows so loud that you have a difficult time hearing the person. This is an example of the physical environment interfering with your perception. The neural structure of the perceiver can make a difference as well; if the person has some sort of neural damage, it can interfere with or alter his or her perceptions of a physical stimulus. People who are red-green color-blind do not have the subjective impressions of green or red. Finally, the motivation of the perceiver can make a difference, especially when a task is difficult. Imagine that you are looking in a Where's Waldo puzzle.