CogLab Homework: Mapping the Blind Spot

due Thursday, Feb. 7

1. Log onto the CogLab web page and click on the link to the "Mapping the Blind Spot" Experiment. Read the directions carefully before starting the experiment so you know what to do! Run through the experiment before midnight on Tuesday, Sept 4. to get full credit.

2. Print out your individual data (see the CogLab Instruction Sheet). You can cut and paste the data output into an Excel Spreadsheet or a Word document (for this experiment it will be a grid of ones and zeros). If you can shrink the output so that each line does not return onto a second line that would be optimal. (shrink the font, widen the margins, print in landscape format, etc.) Explain in your own words what the experiment and data are showing.

3. Print out the following two images on separate sheets of paper.

4. Start with the image of the x and dot. Hold the paper up in front of your face about 8 inches away. Cover your left eye and stare at the x. Move the image away from your face until the black dot disappears (it will be in your peripheral vision). When it does, it has entered your blind spot. Now substitute the image with the bars and stare at the x again. Move the sheet forward and back so that the gap in the bar goes in and out of your blind spot. When the gap between the bars falls into your blind spot you should not "see" any gap between the bars and should instead perceive one solid vertical bar. These two experiences may at first seem incompatible. These results, however, give us information about how the brain organizes and interprets visual information. For your answer, provide an explanation that could account for why the isolated dot would disappear in the blind spot, while the white gap in the vertical bar is perceived as a part of one long black bar? Hint: if you close one eye and look around your surroundings you do not experience a "hole" in your visual field where your blind spot is. You see a complete visual scene. This is the same phenomenon as perceiving the vertical bar as complete.