Chapter 1. Signal Detection Experiment

Introduction

Signal detection theory describes how we go about determining if something happened in a situation where it is not clear that something happened. For example, you are downstairs without a phone, watching a movie, and at an intense moment, you thought you heard the phone ring. You have to decide if the phone rang. The two factors involved are how easy it is to hear the phone (your sensitivity), and how much you want to hear the phone (your criterion). To illustrate criterion, think of waiting to hear about a possible date: You want to hear the phone. Or think of hoping to avoid a call from your parents: You don’t want to hear the phone. In this experiment, we will try to manipulate both sensitivity and criterion to illustrate how this theory can be used in the laboratory to examine some cognitive issues involved in our basic perception.

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

Experiment Setup

Figure 1.1

Instructions

You will be shown a screen full of squares for a short period. Some screens may include a single circle. You are to determine if the circle was present. Before each block of trials, you will be told how your successes and failures will be scored. Your task is to accumulate as many points as possible. For each situation, a goal number of points you should be able to achieve for each situation will be indicated.

Keyboard Responses

Experiment

Figure 1.2

Results

Figure 1.3

Quiz