Signal Detection Theory

Signal Detection Theory is used to help determine how a person might make a decision in an uncertain situation. Experiments typically involve recording when a subject correctly guesses the presence or absence of a stimuli, as well as when a subject falsely chooses one or the other.

Tradeoffs can occur depending on the decision that must be made (depending on if a disease is guessed to be present, then certain expensive or painful treatments must be chosen, or the patient may go home - but treatment will not work if the disease is not present, yet if the disease is ignored, there is risk of greater damage).

Applet

Instructions

Choosing Experiment Variable

Signal Probability - This will specify the probability that a signal will be presented to the subject. Its value must be between 0 and 1 inclusive.
Signal Duration - This value specifies how long the signal will be shown to the subject in milliseconds (1000ms = 1 second). It may have any positive value.
Signal Strength - This value will be the size in pixels of the signal (dot) presented to the subject.
Number of Trials - This controls how many trials will be presented in the experiment (called Block). A number greater than 0 is required.

Starting and Rumning the Experiment

To begin the experiment, press the Start trials button. The subject will be shown a "+" focus in the center of the presentation area. There may also be a signal at a random location in the presentation area. The subject then presses the 'f' key or the 'j' key, depending on whether or not they detected the signal. Pressing the SPACE bar begins the next trial.