Basic Detection Theory and One-Interval Designs
Part I introduces the one-interval design, in which a single stimulus is presented on each trial. The simplest and most important example is a correspondence experiment in which the stimulus is drawn from one of two stimulus classes and the observer tries to say from which class it is drawn. In auditory experiments, for example, the two stimuli might be a weak tone and no sound, tone sequences that may be slow or fast, or passages from the works of Mozart and Beethoven.
We begin by describing the use of one-interval designs to measure discrimination, the ability to tell two stimuli apart. Two types of such experiments may be distinguished. If one of the two stimulus classes contains only the null stimulus, as in the tone-versus-background experiment, the task is called detection. (This historically important application is responsible for the use of the term detection theory to refer to these methods. ) If neither stimulus is null, the experiment is called recognition, as in the other examples. The methods for analyzing detection and recognition are the same, and we make no distinction between them (until chap. 10, where we consider experiments in which the two tasks are combined).
In chapters 1 and 2, we focus on designs with two possible responses as well as two stimulus classes. Because the possible responses in some applications (e.g., the tone detection experiment) are “yes” and “no, ” the paradigm with two stimuli, one interval, and two responses is sometimes termed yes-no even when the actual responses are, say, “slow” and “fast. ” Performance can be analyzed into two distinct elements: the degree to which the observer's responses mirror the stimuli (chap. 1) and the degree to which they display bias (chap. 2). Measuring these two elements requires a theory; we use the most common, normal-distribution variant of detection theory to