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DEPENDENT MEASURES and RESULTS

After you are finished, a results window will appear. (You may want to print this page in order to refer to it after you are finished with the experiment):

The values along the x-axis are comparison line offsets from the true connection point; for example, an offset of 0 means the comparison line was shown at the true connection point; the other offset values mean that the comparison line was located anywhere from -33 pixels below the true connection point to 33 pixels above the true connection point.

The y-axis shows the percentage of "above" responses for those trials showing a comparison line at a given offset. For example, for those trials showing the comparison line at offset = -33, the subject thought the comparison line was below the true connection point each time (i.e., there were 0% "above" responses). For those trials showing the comparison line at offset = -12, the subject thought the comparison line was above the true connection point 70% of the time (30% of the time, the subject thought it was below the true connection point). Note that the curve is color-coded: red indicates the percentage of "above" responses for those trials where the comparison line is actually below the true connection point. The white curve point indicates the percentage of "above" responses for those trials where the comparison line is actually at the true connection point; and green is for those trials where the comparison line is actually above the true connection point.

POINT OF SUBJECTIVE CONNECTION

The point of subjective connection is that offset value where a subject perceives the comparison and standard lines to be connected. For example, assume that the illusion has no effect. In this case, when the comparison line is located at the true connection point, the comparison and standard lines will appear collinear, and we expect a subject to choose "above" 50% of the time and choose "below" the rest of the time (on the graph, the white curve point should be located at point offset = 0 and % above = 50%). This is because a subject does not have theoption to report that the standard and comparison lines are truly connected. Therefore the subject will, most likely, randomly choose a response (i.e., either "above" or "below"). However, if the illusion does have an effect on a subject's perception (i.e., the point of subjective connection will not be equal to the true connect point), then the 50% response rate will lie at some non-zero offset value. The is the case above: the blue line connects the 50% "above" response rate with an offset value of -18. This offset value is the point of subjective connection for the subject. (If the results button is pressed, a dialog box will display the interpolated point of subjective connection). So...what's your point of subjective connection? Try the experiment and see!

These pages maintained by Christopher Currie & Clara Fitzgerald. The applets were created by Christopher Currie.
Send questions concerning this unit or applets to The IPL Development team or to ccurrie@s.psych.uiuc.edu.
(Last update: February 2, 1998).