Bird in the Cage

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In this activity about afterimages, learners explore what happens when receptor cells called cones in your eye's retina get tired. Learners will stare at a simple red shape, such as a bird, glued onto white poster board and then quickly stare at an image of a birdcage. Learners will be surprised to see a bluish-green (cyan) bird in the cage. Learners repeat the process with a green bird and a blue bird to discover what color images appear when their eyes become fatigued.

Quick Guide

Preparation Time:
10 to 30 minutes

Learning Time:
10 to 30 minutes

Estimated Materials Cost:
$1 - $5 per student

Age Range:
Ages 6 - 14

Resource Type:


Materials List (per student)

  • 4 white posterboards or pieces of paper
  • Bright red, green, and blue construction or contact paper
  • Small piece of black construction or contact paper, or black marking pen
  • Scissors
  • Glue or glue stick (if you are using construction paper)
  • Adult help


  • Life Sciences
    • Human Body
      • The Brain and Nervous System
    • Human Senses and Perception
      • Vision
      • Perception
  • Physical Sciences
    • Vibration and Waves
      • Light and Optics
    • Light and Optics
      • Sunlight and Color
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations


To use this activity, learners need to:

  • see
  • see color

Learning styles supported:

  • Involves hands-on or lab activities


This resource is part of:

Access Rights:

  • Free access



Funding Sources:

  • National Science Foundation
  • California Department of Education
  • NEC Foundation of America