The study of illusions provides unique insights into how our brains construct normal, everyday perceptual experience. The Poggendorff illusion falls into the class of distortion illusions. This illusion will distort your perception of continuity--specifically, your perception of a straight line. The activity begins with a few illustrations of the Poggendorff illusion and it's variants. This is followed by an interactive activity in which the student can manipulate the objects that comprise the illusion. Finally, there is a brief (5 minutes) experiment, the results of which reveal the magnitude of judgment error. Attention is given to clarify the independent variable and the experimental design.
Type of Material:
A text-based description and a java applet experiment.
Recommended Uses:
This activity provides an interesting and compelling introduction to one type of visual illusions. It is recommended as an ancillary activity to a more thorough discussion of the topic.
Technical Requirements:
Monitor setting is relevant. Students select their monitor setting prior to beginning the experiment.
Identify Major Learning Goals:
The goal of this website is to provide students with an understanding of distortion-based visual illusions. This activity leads to a better understanding of how humans organize and interpret certain kinds of visual information
Target Student Population:
Undergraduate Psychology students.
Prerequisite Knowledge or Skills:
College-level reading ability required.
Content Quality
Rating:
Strengths:
This activity provides both a cognitive and a hands-on learning experience. The experiential basis of this type of visual illusion is implicitly, rather than explicitly taught. The text material is challenging, and is clearly designed to provide an academic approach to the material. Students are provided immediate feedback on the accuracy of their ability to judge the colinearity of the stimulus lines using an active learning activity that is likely to maintain a high level of attention and result in a fuller understanding of the Poggendorf illusion as well as deception-based illusions in general.
Concerns:
None.
Potential Effectiveness as a Teaching Tool
Rating:
Strengths:
This activity provides an interesting and compelling introduction to one type of visual illusions. It is recommended as an ancillary activity to a more thorough discussion.
Concerns:
None.
Ease of Use for Both Students and Faculty
Rating:
Strengths:
See concerns.
Concerns:
This application requires a java-ready browser, such as any recent release of Netscape Communicator or Internet Explorer. It may also perform better on the Windows (rather than the Macintosh) platform. The experimental trials are very easy to understand and to complete. During the experimental trials the student is asked to judge the colinearity of two lines. A button is provided for "Above" and "Below", but not for "Colinear". The instructions, which may appear counterintuitive, require the subject to press either the "Above" or "Below" buttons "as Random" when the lines are judged to be collinear. A third "Colinear" button might serve to improve the face validity of the experiment.
Creative Commons:
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