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 user ID and password that I have assigned you. Use the Blackboard "Check Grade" function (under Student Tools) to retrieve yours and write them down. The first time you use Coglab you will also need the registration code from the Coglab license you purchased to set up your account.

To set up your Coglab account, go to the coglab web site (http://coglab.wadsworth.com) and scroll down to the bottom of the page where there is a section labeled "Students." Under "Students" click "Access existing account." Read the instructions on that page, and at the bottom enter the username and password I gave you. The username will be something like "allbritton404-1" and the password will be an 8-digit number. After you then click "Submit information" a pop-up window will ask for your registration code. Type in your registration code and click "Register Now." Then follow the instructions on the screen to change your password (if you want to) and begin the experiment. (Note: If you choose to change your password and then forget it, I will not be able to tell you what it is, so do not change the password unless you are sure you can remember it.)

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 by clicking "Home" on the registration page, or going directly to 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 Coglab ID number. 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 Coglab ID ends in 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 Coglab ID ends in 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).