Seeing Different Images in Optical Illusions! Is It a Boy or Girl Thing?

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Author: Muriel Gerhard



Middle School

Difficulty of Project



$5 at most

Safety Issues


Material Availability

Free pictures of optical illusions are readily available at

Approximate Time Required to Complete the Project

One week.  This includes collection, recording and analysis of data, summary of results and completion of bibliography.


To design and conduct an experiment to determine whether there are gender differences when boys and girls view optical illusions?

Materials, Equipment  and Subjects Required

The following  free samples of optical illusions obtained from

  • Crazy Line Trick
  • The Wacky Spiral
  • Rabbit or Duck Illusion
  • The Picture of Many Faces
  • The Circle Illusion

Graph paper for summarizing data. 5 boys and 5 girls of the same age who will volunteer to participate in this experiment.


Background Information

On the information level, this experiment serves to acquaint students with the phenomenon of optical illusions and the question of whether seeing is always believing. They readily learn that things are not always what they seem and that we all do not instantly and consistently see things in the same form or context.

In addition, this science fair experiment also serves to acquaint students with the essential processes of sciencing such as formulating a hypothesis, researching  data to support their hypothesis, identifying dependent and independent variables, using a control when warranted, obtaining an adequate sample of test subjects, collecting and recording  data,  presenting data in a pictorial and / or graphic format and of being able to make better judgments as to the validity and reliability of their findings.  They take on the role of scientists and in the process they learn to act as one.

Research Terms

  • Optics
  • Illusion
  • Physiological
  • Cognitive
  • Depth perception
  • Visual phenomena
  • Paradox
  • Mirage

Research Questions

  • What are optical illusions?
  • What are physiological illusions?
  • What are cognitive illusions?  
  • How do scientists explain these different illusions?
  • How have they been used?
  • Why do you think we see what we do?

Terms, Concepts and Questions to Start Experimental Research

  • What is a control?  A control is the variable that is not changed in the experiment.
  • What purpose does a control serve? It is used to make comparisons as to what changed or possibly caused the change.
  • Note: Not every experiment requires a control. In this case, none is needed.
  • What are variables?  Variables are factors that can be changed in an experiment.
  • What is an independent variable? The independent variable is the one that is changed in the experiment.
  • What is a dependent variable? The dependent variable is the one that changes as a result of the change in the independent variable.

Charting Data

In this experiment, use charts to display the obtained data such the following sample:

Question:  What did you see?

Subjects: Girls

Crazy Line

Wacky Spiral

Rabbit or Duck

Picture of Many Faces

Circle Illusion































Construct a similar chart for boys.  Use a full page for each chart, providing ample space for subjects to record their observations. You may choose to graph these data and display the resultant graphs. A picture is always worth a thousand words!

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