Coglab Instructions: Signal Detection

This experiment will demonstrate the Signal Detection Theory concepts of bias and discriminability. Your data will be recorded automatically by Coglab, and we will use that data in our discussion of Signal Detection Theory in class.

Special Instructions for Using Coglab for the First Time

To use Coglab in this course, you will need the course ID and password. See the Blackboard "Course Documents" section for the information you need to get started with Coglab. The first time you use Coglab you will also need the registration code from the Coglab license you purchased to set up your account.

Doing the Experiment

Once your account is set up, you are ready to begin the experiment. First go back to the main Coglab web page - http://coglab.wadsworth.com. Click on "Signal Detection" in the Perception group. Read the background and instructions for the experiment. Before you begin, also read the additional instructions provided here.

Additional Instructions for this Experiment

The task in the experiment demonstration will be to detect whether a line of dots in a straight row is present within a field of randomly arranged dots. On each trial you will respond “yes” or “no” by pressing the keys that the instructions tell you to use. The computer will record your responses and, at the end of the experiment, tell you your results.

Bias Manipulation. In addition to following the instructions given on the Coglab web pages, use the following instructions to guide your decision-making in the experiment. These instructions manipulate your response bias, a concept we will discuss in relation to signal detection theory. We will divide the class into two groups based on your birth date. Follow the instructions for your group when doing the experiment. Allow the instructions to bias how careful you are in deciding whether the line is present or not, but do not simply answer the same thing every time (always “yes” or always “no”).

Positive Bias Group – if your birth date is an odd number
Pretend that you will be paid $3 for each line that you correctly detect (each hit) and penalized $1 for each time you incorrectly say “yes” when the line is absent (each false alarm).
Negative Bias Group – if your birth date is an even number
Pretend that you will be paid $1 for each line that you correctly say “yes” when the line is present (each hit) and penalized $3 for each time you incorrectly say “yes” when the line is absent (each false alarm).