Chapter 1. Signal Detection Theory

Introduction

You are downstairs watching a movie. The volume is up on your surround sound system and you don’t have a phone in the room. At a moment of great tension and excitement, and perhaps volume, you think you hear the phone. You are not sure. What are you to do?

Most of the time, we are aware of our surroundings. You can easily identify the door in the room you are in. It is obvious, but there are times when something happens, like the phone ringing, and you have to decide if something has actually happened. Signal detection theory was developed to explain these ambiguous situations.

This activity will use a simulated experiment to guide you through the elements of signal detection theory and how it describes how you determine if you think the phone actually rang.

Green, D. M., & Swets, J. A. (1966). Signal detection theory and psychophysics. Oxford England: John Wiley.

Experiment Setup

Figure 1.1

Instructions

In this experiment, you have to determine if something has changed on the screen. The situation is very simple. Dots will flash on the screen in front of you; sometimes there will be more dots than others. It is all random. Your job is to determine if the experimenter has added any dots to the screen.

Please follow the instructions on the experiment tab as you go through the activity to illustrate the elements of signal detection theory.

Experiment

Figure 1.2

Results

Figure 1.3

Quiz